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which describes the associated sum of squares, while the same is true for "treatments" if there is no treatment effect. see also lack-of-fit sum of squares. the f-test the f-test is used for comparing the factors of the total deviation. for example, in one-way, or single-factor anova, statistical significance is tested for by comparing the f test statistic where ms is mean square, is the number of treatments and is the total number of cases to the f-distribution with , degrees of freedom. using the f-distribution is a natural candidate because the test statistic is the ratio of two scaled sums of squares each of which follows a scaled chi-squared distribution. the expected value of f is (where is the treatment sample size) which is 1 for no treatment effect. as values of f increase above 1, the evidence

is increasingly inconsistent with the null hypothesis. two apparent experimental methods of increasing f are increasing the sample size and reducing the error variance by tight experimental controls. there are two methods of concluding the anova hypothesis test, both of which produce the same result: the textbook method is to compare the observed value of f with the critical value of f determined from tables. the critical value of f is a function of the degrees of freedom of the numerator and the denominator and the significance level (). if f fcritical, the null hypothesis is rejected. the computer method calculates the probability (p-value) of a value of f greater than or equal to the observed value. the null hypothesis is rejected if this probability is less than or equal to the significance level (). the

anova f-test is known to be nearly optimal in the sense of minimizing false negative errors for a fixed rate of false positive errors (i.e. maximizing power for a fixed significance level). for example, to test the hypothesis that various medical treatments have exactly the same effect, the f-test's p-values closely approximate the permutation test's p-values: the approximation is particularly close when the design is balanced. such permutation tests characterize tests with maximum power against all alternative hypotheses, as observed by rosenbaum. the anova f-test (of the null-hypothesis that all treatments have exactly the same effect) is recommended as a practical test, because of its robustness against many alternative distributions. extended logic anova consists of separable parts; partitioning sources

of variance and hypothesis testing can be used individually. anova is used to support other statistical tools. regression is first used to fit more complex models to data, then anova is used to compare models with the objective of selecting simple(r) models that adequately describe the data. "such models could be fit without any reference to anova, but anova tools could then be used to make some sense of the fitted models, and to test hypotheses about batches of coefficients." "[w]e think of the analysis of variance as a way of understanding and structuring multilevel modelsnot as an alternative to regression but as a tool for summarizing complex high-dimensional inferences..." for a single factor the simplest experiment suitable for anova analysis is the completely randomized experiment with a single factor.

more complex experiments with a single factor involve constraints on randomization and include completely randomized blocks and latin squares (and variants: graeco-latin squares, etc.). the more complex experiments share many of the complexities of multiple factors. a relatively complete discussion of the analysis (models, data summaries, anova table) of the completely randomized experiment is available. there are some alternatives to conventional one-way analysis of variance, e.g.: welch's heteroscedastic f test, welch's heteroscedastic f test with trimmed means and winsorized variances, brown-forsythe test, alexander-govern test, james second order test and kruskal-wallis test, available in onewaytests r it is useful to represent each data point in the following form, called a statistical model: where i

= 1, 2, 3, , r j = 1, 2, 3, , c = overall average (mean) j = differential effect (response) associated with the j level of x; this assumes that overall the values of j add to zero (that is, ) ij = noise or error associated with the particular ij data value that is, we envision an additive model that says every data point can be represented by summing three quantities: the true mean, averaged over all factor levels being investigated, plus an incremental component associated with the particular column (factor level), plus a final component associated with everything else affecting that specific data value. for multiple factors anova generalizes to the study of the effects of multiple factors. when the experiment includes observations at all combinations of levels of each factor, it is termed factorial.

factorial experiments are more efficient than a series of single factor experiments and the efficiency grows as the number of factors increases. consequently, factorial designs are heavily used. the use of anova to study the effects of multiple factors has a complication. in a 3-way anova with factors x, y and z, the anova model includes terms for the main effects (x, y, z) and terms for interactions (xy, xz, yz, xyz). all terms require hypothesis tests. the proliferation of interaction terms increases the risk that some hypothesis test will produce a false positive by chance. fortunately, experience says that high order interactions are rare. the ability to detect interactions is a major advantage of multiple factor anova. testing one factor at a time hides interactions, but produces apparently inconsistent

experimental results. caution is advised when encountering interactions; test interaction terms first and expand the analysis beyond anova if interactions are found. texts vary in their recommendations regarding the continuation of the anova procedure after encountering an interaction. interactions complicate the interpretation of experimental data. neither the calculations of significance nor the estimated treatment effects can be taken at face value. "a significant interaction will often mask the significance of main effects." graphical methods are recommended to enhance understanding. regression is often useful. a lengthy discussion of interactions is available in cox (1958). some interactions can be removed (by transformations) while others cannot. a variety of techniques are used with multiple factor anova

to reduce expense. one technique used in factorial designs is to minimize replication (possibly no replication with support of analytical trickery) and to combine groups when effects are found to be statistically (or practically) insignificant. an experiment with many insignificant factors may collapse into one with a few factors supported by many replications. associated analysis some analysis is required in support of the design of the experiment while other analysis is performed after changes in the factors are formally found to produce statistically significant changes in the responses. because experimentation is iterative, the results of one experiment alter plans for following experiments. preparatory analysis the number of experimental units in the design of an experiment, the number of experimental

units is planned to satisfy the goals of the experiment. experimentation is often sequential. early experiments are often designed to provide mean-unbiased estimates of treatment effects and of experimental error. later experiments are often designed to test a hypothesis that a treatment effect has an important magnitude; in this case, the number of experimental units is chosen so that the experiment is within budget and has adequate power, among other goals. reporting sample size analysis is generally required in psychology. "provide information on sample size and the process that led to sample size decisions." the analysis, which is written in the experimental protocol before the experiment is conducted, is examined in grant applications and administrative review boards. besides the power analysis, there

are less formal methods for selecting the number of experimental units. these include graphical methods based on limiting the probability of false negative errors, graphical methods based on an expected variation increase (above the residuals) and methods based on achieving a desired confidence interval. power analysis power analysis is often applied in the context of anova in order to assess the probability of successfully rejecting the null hypothesis if we assume a certain anova design, effect size in the population, sample size and significance level. power analysis can assist in study design by determining what sample size would be required in order to have a reasonable chance of rejecting the null hypothesis when the alternative hypothesis is true. effect size several standardized measures of effect

have been proposed for anova to summarize the strength of the association between a predictor(s) and the dependent variable or the overall standardized difference of the complete model. standardized effect-size estimates facilitate comparison of findings across studies and disciplines. however, while standardized effect sizes are commonly used in much of the professional literature, a non-standardized measure of effect size that has immediately "meaningful" units may be preferable for reporting purposes. model confirmation sometimes tests are conducted to determine whether the assumptions of anova appear to be violated. residuals are examined or analyzed to confirm homoscedasticity and gross normality. residuals should have the appearance of (zero mean normal distribution) noise when plotted as a function of

anything including time and modeled data values. trends hint at interactions among factors or among observations. follow-up tests a statistically significant effect in anova is often followed by additional tests. this can be done in order to assess which groups are different from which other groups or to test various other focused hypotheses. follow-up tests are often distinguished in terms of whether they are "planned" (a priori) or "post hoc." planned tests are determined before looking at the data, and post hoc tests are conceived only after looking at the data (though the term "post hoc" is inconsistently used). the follow-up tests may be "simple" pairwise comparisons of individual group means or may be "compound" comparisons (e.g., comparing the mean pooling across groups a, b and c to the mean of group

d). comparisons can also look at tests of trend, such as linear and quadratic relationships, when the independent variable involves ordered levels. often the follow-up tests incorporate a method of adjusting for the multiple comparisons problem. study designs there are several types of anova. many statisticians base anova on the design of the experiment, especially on the protocol that specifies the random assignment of treatments to subjects; the protocol's description of the assignment mechanism should include a specification of the structure of the treatments and of any blocking. it is also common to apply anova to observational data using an appropriate statistical model. some popular designs use the following types of anova: one-way anova is used to test for differences among two or more independent groups

(means), e.g. different levels of urea application in a crop, or different levels of antibiotic action on several different bacterial species, or different levels of effect of some medicine on groups of patients. however, should these groups not be independent, and there is an order in the groups (such as mild, moderate and severe disease), or in the dose of a drug (such as 5mg/ml, 10mg/ml, 20mg/ml) given to the same group of patients, then a linear trend estimation should be used. typically, however, the one-way anova is used to test for differences among at least three groups, since the two-group case can be covered by a t-test. when there are only two means to compare, the t-test and the anova f-test are equivalent; the relation between anova and t is given by . factorial anova is used when there is more than

one factor. repeated measures anova is used when the same subjects are used for each factor (e.g., in a longitudinal study). multivariate analysis of variance (manova) is used when there is more than one response variable. cautions balanced experiments (those with an equal sample size for each treatment) are relatively easy to interpret; unbalanced experiments offer more complexity. for single-factor (one-way) anova, the adjustment for unbalanced data is easy, but the unbalanced analysis lacks both robustness and power. for more complex designs the lack of balance leads to further complications. "the orthogonality property of main effects and interactions present in balanced data does not carry over to the unbalanced case. this means that the usual analysis of variance techniques do not apply. consequently,

the analysis of unbalanced factorials is much more difficult than that for balanced designs." in the general case, "the analysis of variance can also be applied to unbalanced data, but then the sums of squares, mean squares, and f-ratios will depend on the order in which the sources of variation are considered." anova is (in part) a test of statistical significance. the american psychological association (and many other organisations) holds the view that simply reporting statistical significance is insufficient and that reporting confidence bounds is preferred. generalizations anova is considered to be a special case of linear regression which in turn is a special case of the general linear model. all consider the observations to be the sum of a model (fit) and a residual (error) to be minimized. the kruskalwallis

test and the friedman test are nonparametric tests, which do not rely on an assumption of normality. connection to linear regression below we make clear the connection between multi-way anova and linear regression. linearly re-order the data so that -th observation is associated with a response and factors where denotes the different factors and is the total number of factors. in one-way anova and in two-way anova . furthermore, we assume the -th factor has levels, namely . now, we can one-hot encode the factors into the dimensional vector . the one-hot encoding function is defined such that the -th entry of is the vector is the concatenation of all of the above vectors for all . thus, . in order to obtain a fully general -way interaction anova we must also concatenate every additional interaction term in

the vector and then add an intercept term. let that vector be . with this notation in place, we now have the exact connection with linear regression. we simply regress response against the vector . however, there is a concern about identifiability. in order to overcome such issues we assume that the sum of the parameters within each set of interactions is equal to zero. from here, one can use f-statistics or other methods to determine the relevance of the individual factors. example we can consider the 2-way interaction example where we assume that the first factor has 2 levels and the second factor has 3 levels. define if and if , i.e. is the one-hot encoding of the first factor and is the one-hot encoding of the second factor. with that, where the last term is an intercept term. for a more concrete example

suppose that then, see also anova on ranks anova-simultaneous component analysis analysis of covariance (ancova) analysis of molecular variance (amova) analysis of rhythmic variance (anorva) explained variation linear trend estimation mixed-design analysis of variance multivariate analysis of covariance (mancova) permutational analysis of variance variance decomposition expected mean squares footnotes notes references pre-publication chapters are available on-line. cohen, jacob (1988). statistical power analysis for the behavior sciences (2nd ed.). routledge cox, david r. (1958). planning of experiments. reprinted as freedman, david a.(2005). statistical models: theory and practice, cambridge university press. lehmann, e.l. (1959) testing statistical hypotheses. john wiley & sons.

moore, david s. & mccabe, george p. (2003). introduction to the practice of statistics (4e). w h freeman & co. rosenbaum, paul r. (2002). observational studies (2nd ed.). new york: springer-verlag. further reading cox, david r. & reid, nancy m. (2000). the theory of design of experiments. (chapman & hall/crc). freedman, david a.; pisani, robert; purves, roger (2007) statistics, 4th edition. w.w. norton & company tabachnick, barbara g. & fidell, linda s. (2007). using multivariate statistics (5th ed.). boston: pearson international edition. external links socr anova activity examples of all anova and ancova models with up to three treatment factors, including randomized block, split plot, repeated measures, and latin squares, and their analysis in r (university of southampton) nist/sematech

in organic chemistry, an alkane, or paraffin (a historical trivial name that also has other meanings), is an acyclic saturated hydrocarbon. in other words, an alkane consists of hydrogen and carbon atoms arranged in a tree structure in which all the carboncarbon bonds are single. alkanes have the general chemical formula . the alkanes range in complexity from the simplest case of methane (), where n=1 (sometimes called the parent molecule), to arbitrarily large and complex molecules, like pentacontane () or 6-ethyl-2-methyl-5-(1-methylethyl) octane, an isomer of tetradecane (). the international union of pure and applied chemistry (iupac) defines alkanes as "acyclic branched or unbranched hydrocarbons having the general formula , and therefore consisting entirely of hydrogen atoms and saturated carbon atoms".

however, some sources use the term to denote any saturated hydrocarbon, including those that are either monocyclic (i.e. the cycloalkanes) or polycyclic, despite their having a distinct general formula (i.e. cycloalkanes are ). in an alkane, each carbon atom is sp3-hybridized with 4 sigma bonds (either cc or ch), and each hydrogen atom is joined to one of the carbon atoms (in a ch bond). the longest series of linked carbon atoms in a molecule is known as its carbon skeleton or carbon backbone. the number of carbon atoms may be considered as the size of the alkane. one group of the higher alkanes are waxes, solids at standard ambient temperature and pressure (satp), for which the number of carbon atoms in the carbon backbone is greater than about 17. with their repeated units, the alkanes constitute a homologous

series of organic compounds in which the members differ in molecular mass by multiples of 14.03u (the total mass of each such methylene-bridge unit, which comprises a single carbon atom of mass 12.01u and two hydrogen atoms of mass ~1.01u each). methane is produced by methanogenic bacteria and some long-chain alkanes function as pheromones in certain animal species or as protective waxes in plants and fungi. nevertheless, most alkanes do not have much biological activity. they can be viewed as molecular trees upon which can be hung the more active/reactive functional groups of biological molecules. the alkanes have two main commercial sources: petroleum (crude oil) and natural gas. an alkyl group is an alkane-based molecular fragment that bears one open valence for bonding. they are generally abbreviated with

the symbol for any organyl group, r, although alk is sometimes used to specifically symbolize an alkyl group (as opposed to an alkenyl group or aryl group). structure and classification ordinarily the c-c single bond distance is . saturated hydrocarbons can be linear, branched, or cyclic. the third group is sometimes called cycloalkanes. very complicated structures are possible by combining linear, branch, cyclic alkanes. isomerism alkanes with more than three carbon atoms can be arranged in various ways, forming structural isomers. the simplest isomer of an alkane is the one in which the carbon atoms are arranged in a single chain with no branches. this isomer is sometimes called the n-isomer (n for "normal", although it is not necessarily the most common). however, the chain of carbon atoms may also be

branched at one or more points. the number of possible isomers increases rapidly with the number of carbon atoms. for example, for acyclic alkanes: c1: methane only c2: ethane only c3: propane only c4: 2 isomers: butane and isobutane c5: 3 isomers: pentane, isopentane, and neopentane c6: 5 isomers: hexane, 2-methylpentane, 3-methylpentane, 2,2-dimethylbutane, and 2,3-dimethylbutane c7: 9 isomers: heptane, methylhexane (2 isomers), dimethylpentane (4 isomers), 3-ethylpentane, 2,2,3-trimethylbutane c8: 18 isomers: octane, 2-methylheptane, 3-methylheptane, 2,3-dimethylhexane, 3,4-dimethylhexane, 2,3,4-trimethylpentane, 3,3-dimethylhexane, 2,2-trimethylpentane, 2,4-dimethylhexane, 2,2,4-trimethylpentane, 2,3,3-trimethylpentane, 3,3,4-trimethyl-pentane, 3,4,4-trimethylpentane, 2,4,4-trimethylpentane, (5 isomers)

c9: 35 isomers c10: 75 isomers c12: 355 isomers c32: 27,711,253,769 isomers c60: 22,158,734,535,770,411,074,184 isomers, many of which are not stable. branched alkanes can be chiral. for example, 3-methylhexane and its higher homologues are chiral due to their stereogenic center at carbon atom number 3. the above list only includes differences of connectivity, not stereochemistry. in addition to the alkane isomers, the chain of carbon atoms may form one or more rings. such compounds are called cycloalkanes, and are also excluded from the above list because changing the number of rings changes the molecular formula. for example, cyclobutane and methylcyclopropane are isomers of each other (c4h8), but are not isomers of butane (c4h10). nomenclature the iupac nomenclature (systematic way of naming compounds)

for alkanes is based on identifying hydrocarbon chains. unbranched, saturated hydrocarbon chains are named systematically with a greek numerical prefix denoting the number of carbons and the suffix "-ane". in 1866, august wilhelm von hofmann suggested systematizing nomenclature by using the whole sequence of vowels a, e, i, o and u to create suffixes -ane, -ene, -ine (or -yne), -one, -une, for the hydrocarbons cnh2n+2, cnh2n, cnh2n2, cnh2n4, cnh2n6. in modern nomenclature, the first three specifically name hydrocarbons with single, double and triple bonds; while "-one" now represents a ketone. linear alkanes straight-chain alkanes are sometimes indicated by the prefix "n-" or "n-"(for "normal") where a non-linear isomer exists. although this is not strictly necessary and is not part of the iupac naming system,

the usage is still common in cases where one wishes to emphasize or distinguish between the straight-chain and branched-chain isomers, e.g., "n-butane" rather than simply "butane" to differentiate it from isobutane. alternative names for this group used in the petroleum industry are linear paraffins or n-paraffins. the first six members of the series (in terms of number of carbon atoms) are named as follows: methane ch4 one carbon and 4 hydrogen ethane c2h6 two carbon and 6 hydrogen propane c3h8 three carbon and 8 hydrogen butane c4h10 four carbon and 10 hydrogen pentane c5h12 five carbon and 12 hydrogen hexane c6h14 six carbon and 14 hydrogen the first four names were derived from methanol, ether, propionic acid and butyric acid. alkanes with five or more carbon atoms are named by adding the suffix

-ane to the appropriate numerical multiplier prefix with elision of any terminal vowel (-a or -o) from the basic numerical term. hence, pentane, c5h12; hexane, c6h14; heptane, c7h16; octane, c8h18; etc. the numeral prefix is generally greek, however alkanes with a carbon atom count ending in nine, for example nonane, use the latin prefix non-. for a more complete list, see list of straight-chain alkanes. branched alkanes simple branched alkanes often have a common name using a prefix to distinguish them from linear alkanes, for example n-pentane, isopentane, and neopentane. iupac naming conventions can be used to produce a systematic name. the key steps in the naming of more complicated branched alkanes are as follows: identify the longest continuous chain of carbon atoms name this longest root chain using

standard naming rules name each side chain by changing the suffix of the name of the alkane from "-ane" to "-yl" number the longest continuous chain in order to give the lowest possible numbers for the side-chains number and name the side chains before the name of the root chain if there are multiple side chains of the same type, use prefixes such as "di-" and "tri-" to indicate it as such, and number each one. add side chain names in alphabetical (disregarding "di-" etc. prefixes) order in front of the name of the root chain saturated cyclic hydrocarbons though technically distinct from the alkanes, this class of hydrocarbons is referred to by some as the "cyclic alkanes." as their description implies, they contain one or more rings. simple cycloalkanes have a prefix "cyclo-" to distinguish them from

alkanes. cycloalkanes are named as per their acyclic counterparts with respect to the number of carbon atoms in their backbones, e.g., cyclopentane (c5h10) is a cycloalkane with 5 carbon atoms just like pentane (c5h12), but they are joined up in a five-membered ring. in a similar manner, propane and cyclopropane, butane and cyclobutane, etc. substituted cycloalkanes are named similarly to substituted alkanes the cycloalkane ring is stated, and the substituents are according to their position on the ring, with the numbering decided by the cahningoldprelog priority rules. trivial/common names the trivial (non-systematic) name for alkanes is 'paraffins'. together, alkanes are known as the 'paraffin series'. trivial names for compounds are usually historical artifacts. they were coined before the development

of systematic names, and have been retained due to familiar usage in industry. cycloalkanes are also called naphthenes. branched-chain alkanes are called isoparaffins. "paraffin" is a general term and often does not distinguish between pure compounds and mixtures of isomers, i.e., compounds of the same chemical formula, e.g., pentane and isopentane. in iupac the following trivial names are retained in the iupac system: isobutane for 2-methylpropane isopentane for 2-methylbutane neopentane for 2,2-dimethylpropane. non-iupac some non-iupac trivial names are occasionally used: cetane, for hexadecane cerane, for hexacosane physical properties all alkanes are colorless. alkanes with the lowest molecular weights are gasses, those of intermediate molecular weight are liquids, and the heaviest are waxy solids. table

of alkanes boiling point alkanes experience intermolecular van der waals forces. stronger intermolecular van der waals forces give rise to greater boiling points of alkanes. there are two determinants for the strength of the van der waals forces: the number of electrons surrounding the molecule, which increases with the alkane's molecular weight the surface area of the molecule under standard conditions, from ch4 to c4h10 alkanes are gaseous; from c5h12 to c17h36 they are liquids; and after c18h38 they are solids. as the boiling point of alkanes is primarily determined by weight, it should not be a surprise that the boiling point has almost a linear relationship with the size (molecular weight) of the molecule. as a rule of thumb, the boiling point rises 2030c for each carbon added to the chain; this rule

applies to other homologous series. a straight-chain alkane will have a boiling point higher than a branched-chain alkane due to the greater surface area in contact, thus the greater van der waals forces, between adjacent molecules. for example, compare isobutane (2-methylpropane) and n-butane (butane), which boil at 12 and 0c, and 2,2-dimethylbutane and 2,3-dimethylbutane which boil at 50 and 58c, respectively. on the other hand, cycloalkanes tend to have higher boiling points than their linear counterparts due to the locked conformations of the molecules, which give a plane of intermolecular contact. melting points the melting points of the alkanes follow a similar trend to boiling points for the same reason as outlined above. that is, (all other things being equal) the larger the molecule the higher the

melting point. there is one significant difference between boiling points and melting points. solids have more rigid and fixed structure than liquids. this rigid structure requires energy to break down. thus the better put together solid structures will require more energy to break apart. for alkanes, this can be seen from the graph above (i.e., the blue line). the odd-numbered alkanes have a lower trend in melting points than even numbered alkanes. this is because even numbered alkanes pack well in the solid phase, forming a well-organized structure, which requires more energy to break apart. the odd-numbered alkanes pack less well and so the "looser" organized solid packing structure requires less energy to break apart. for a visualization of the crystal structures see. the melting points of branched-chain

alkanes can be either higher or lower than those of the corresponding straight-chain alkanes, again depending on the ability of the alkane in question to pack well in the solid phase. conductivity and solubility alkanes do not conduct electricity in any way, nor are they substantially polarized by an electric field. for this reason, they do not form hydrogen bonds and are insoluble in polar solvents such as water. since the hydrogen bonds between individual water molecules are aligned away from an alkane molecule, the coexistence of an alkane and water leads to an increase in molecular order (a reduction in entropy). as there is no significant bonding between water molecules and alkane molecules, the second law of thermodynamics suggests that this reduction in entropy should be minimized by minimizing the contact

between alkane and water: alkanes are said to be hydrophobic as they are insoluble in water. their solubility in nonpolar solvents is relatively high, a property that is called lipophilicity. alkanes are, for example, miscible in all proportions among themselves. the density of the alkanes usually increases with the number of carbon atoms but remains less than that of water. hence, alkanes form the upper layer in an alkanewater mixture. molecular geometry the molecular structure of the alkanes directly affects their physical and chemical characteristics. it is derived from the electron configuration of carbon, which has four valence electrons. the carbon atoms in alkanes are described as sp3 hybrids, that is to say that, to a good approximation, the valence electrons are in orbitals directed towards the corners

of a tetrahedron which are derived from the combination of the 2s orbital and the three 2p orbitals. geometrically, the angle between the bonds are cos1()109.47. this is exact for the case of methane, while larger alkanes containing a combination of ch and cc bonds generally have bonds that are within several degrees of this idealized value. bond lengths and bond angles an alkane has only ch and cc single bonds. the former result from the overlap of an sp3 orbital of carbon with the 1s orbital of a hydrogen; the latter by the overlap of two sp3 orbitals on adjacent carbon atoms. the bond lengths amount to 1.091010m for a ch bond and 1.541010m for a cc bond. the spatial arrangement of the bonds is similar to that of the four sp3 orbitalsthey are tetrahedrally arranged, with an angle of 109.47 between them. structural

formulae that represent the bonds as being at right angles to one another, while both common and useful, do not accurately depict the geometry. conformation the structural formula and the bond angles are not usually sufficient to completely describe the geometry of a molecule. there is a further degree of freedom for each carboncarbon bond: the torsion angle between the atoms or groups bound to the atoms at each end of the bond. the spatial arrangement described by the torsion angles of the molecule is known as its conformation. ethane forms the simplest case for studying the conformation of alkanes, as there is only one cc bond. if one looks down the axis of the cc bond, one will see the so-called newman projection. the hydrogen atoms on both the front and rear carbon atoms have an angle of 120 between them,

resulting from the projection of the base of the tetrahedron onto a flat plane. however, the torsion angle between a given hydrogen atom attached to the front carbon and a given hydrogen atom attached to the rear carbon can vary freely between 0 and 360. this is a consequence of the free rotation about a carboncarbon single bond. despite this apparent freedom, only two limiting conformations are important: eclipsed conformation and staggered conformation. the two conformations differ in energy: the staggered conformation is 12.6kj/mol (3.0 kcal/mol) lower in energy (more stable) than the eclipsed conformation (the least stable). this difference in energy between the two conformations, known as the torsion energy, is low compared to the thermal energy of an ethane molecule at ambient temperature. there is constant

rotation about the cc bond. the time taken for an ethane molecule to pass from one staggered conformation to the next, equivalent to the rotation of one ch3 group by 120 relative to the other, is of the order of 1011seconds. the case of higher alkanes is more complex but based on similar principles, with the antiperiplanar conformation always being the most favored around each carboncarbon bond. for this reason, alkanes are usually shown in a zigzag arrangement in diagrams or in models. the actual structure will always differ somewhat from these idealized forms, as the differences in energy between the conformations are small compared to the thermal energy of the molecules: alkane molecules have no fixed structural form, whatever the models may suggest. spectroscopic properties virtually all organic compounds

contain carboncarbon, and carbonhydrogen bonds, and so show some of the features of alkanes in their spectra. alkanes are notable for having no other groups, and therefore for the absence of other characteristic spectroscopic features of a functional group like oh, cho, cooh etc. infrared spectroscopy the carbonhydrogen stretching mode gives a strong absorption between 2850 and 2960cm1, while the carboncarbon stretching mode absorbs between 800 and 1300cm1. the carbonhydrogen bending modes depend on the nature of the group: methyl groups show bands at 1450cm1 and 1375cm1, while methylene groups show bands at 1465cm1 and 1450cm1. carbon chains with more than four carbon atoms show a weak absorption at around 725cm1. nmr spectroscopy the proton resonances of alkanes are usually found at h = 0.51.5. the carbon-13

resonances depend on the number of hydrogen atoms attached to the carbon: c = 830 (primary, methyl, ch3), 1555 (secondary, methylene, ch2), 2060 (tertiary, methyne, ch) and quaternary. the carbon-13 resonance of quaternary carbon atoms is characteristically weak, due to the lack of nuclear overhauser effect and the long relaxation time, and can be missed in weak samples, or samples that have not been run for a sufficiently long time. mass spectrometry alkanes have a high ionization energy, and the molecular ion is usually weak. the fragmentation pattern can be difficult to interpret, but, in the case of branched chain alkanes, the carbon chain is preferentially cleaved at tertiary or quaternary carbons due to the relative stability of the resulting free radicals. the fragment resulting from the loss of a single

methyl group (m15) is often absent, and other fragments are often spaced by intervals of fourteen mass units, corresponding to sequential loss of ch2 groups. chemical properties alkanes are only weakly reactive with most chemical compounds. the acid dissociation constant (pka) values of all alkanes are estimated to range from 50 to 70, depending on the extrapolation method, hence they are extremely weak acids that are practically inert to bases (see: carbon acids). they are also extremely weak bases, undergoing no observable protonation in pure sulfuric acid (h0 ~ 12), although superacids that are at least millions of times stronger have been known to protonate them to give hypercoordinate alkanium ions (see: methanium ion). similarly, they only show reactivity with the strongest of electrophilic reagents (e.g.,

dioxiranes and salts containing the nf4+ cation). by virtue of their strongly ch bonds (~100 kcal/mol) and cc bonds (~90 kcal/mol, but usually less sterically accessible), they are also relatively unreactive toward free radicals, although many electron-deficient radicals will react with alkanes in the absence of other electron-rich bonds (see below). this inertness is the source of the term paraffins (with the meaning here of "lacking affinity"). in crude oil the alkane molecules have remained chemically unchanged for millions of years. free radicals, molecules with unpaired electrons, play a large role in most reactions of alkanes, such as cracking and reformation where long-chain alkanes are converted into shorter-chain alkanes and straight-chain alkanes into branched-chain isomers. moreover, redox reactions

of alkanes involving free radical intermediates, in particular with oxygen and the halogens, are possible as the carbon atoms are in a strongly reduced state; in the case of methane, carbon is in its lowest possible oxidation state (4). reaction with oxygen (if present in sufficient quantity to satisfy the reaction stoichiometry) leads to combustion without any smoke, producing carbon dioxide and water. free radical halogenation reactions occur with halogens, leading to the production of haloalkanes. in addition, alkanes have been shown to interact with, and bind to, certain transition metal complexes in ch bond activation reactions. in highly branched alkanes, the bond angle may differ significantly from the optimal value (109.5) to accommodate bulky groups. such distortions introduce a tension in the molecule,

known as steric hindrance or strain. strain substantially increases reactivity. however, in general and perhaps surprisingly, when branching is not extensive enough to make highly disfavorable 1,2- and 1,3-alkylalkyl steric interactions (worth ~3.1 kcal/mol and ~3.7 kcal/mol in the case of the eclipsing conformations of butane and pentane, respectively) unavoidable, the branched alkanes are actually more thermodynamically stable than their linear (or less branched) isomers. for example, the highly branched 2,2,3,3-tetramethylbutane is about 1.9 kcal/mol more stable than its linear isomer, n-octane. due to the subtlety of this effect, the exact reasons for this rule have been vigorously debated in the chemical literature and is yet unsettled. several explanations, including stabilization of branched alkanes by

electron correlation, destabilization of linear alkanes by steric repulsion, stabilization by neutral hyperconjugation, and/or electrostatic effects have been advanced as possibilities. the controversy is related to the question of whether the traditional explanation of hyperconjugation is the primary factor governing the stability of alkyl radicals. reactions with oxygen (combustion reaction) all alkanes react with oxygen in a combustion reaction, although they become increasingly difficult to ignite as the number of carbon atoms increases. the general equation for complete combustion is: cnh2n+2 + (n+)o2 (n+1)h2o + nco2 or cnh2n+2 + ()o2 (n+1)h2o + nco2 in the absence of sufficient oxygen, carbon monoxide or even soot can be formed, as shown below: cnh2n+2 + (n+)o2 (n+1)h2o + nco cnh2n+2 + (n+)o2 (n+1)h2o

+ nc for example, methane: 2ch4 + 3o2 4h2o + 2co ch4 + o2 2h2o + c see the alkane heat of formation table for detailed data. the standard enthalpy change of combustion, ch, for alkanes increases by about 650kj/mol per ch2 group. branched-chain alkanes have lower values of ch than straight-chain alkanes of the same number of carbon atoms, and so can be seen to be somewhat more stable. reactions with halogens alkanes react with halogens in a so-called free radical halogenation reaction. the hydrogen atoms of the alkane are progressively replaced by halogen atoms. free radicals are the reactive species that participate in the reaction, which usually leads to a mixture of products. the reaction is highly exothermic with halogen fluorine and can lead to an explosion. these reactions are an important industrial

route to halogenated hydrocarbons. there are three steps: initiation the halogen radicals form by homolysis. usually, energy in the form of heat or light is required. chain reaction or propagation then takes placethe halogen radical abstracts a hydrogen from the alkane to give an alkyl radical. this reacts further. chain termination where the radicals recombine. experiments have shown that all halogenation produces a mixture of all possible isomers, indicating that all hydrogen atoms are susceptible to reaction. the mixture produced, however, is not a statistical mixture: secondary and tertiary hydrogen atoms are preferentially replaced due to the greater stability of secondary and tertiary free-radicals. an example can be seen in the monobromination of propane: cracking cracking breaks larger molecules

into smaller ones. this can be done with a thermal or catalytic method. the thermal cracking process follows a homolytic mechanism with formation of free radicals. the catalytic cracking process involves the presence of acid catalysts (usually solid acids such as silica-alumina and zeolites), which promote a heterolytic (asymmetric) breakage of bonds yielding pairs of ions of opposite charges, usually a carbocation and the very unstable hydride anion. carbon-localized free radicals and cations are both highly unstable and undergo processes of chain rearrangement, cc scission in position beta (i.e., cracking) and intra- and intermolecular hydrogen transfer or hydride transfer. in both types of processes, the corresponding reactive intermediates (radicals, ions) are permanently regenerated, and thus they proceed

by a self-propagating chain mechanism. the chain of reactions is eventually terminated by radical or ion recombination. isomerization and reformation dragan and his colleague were the first to report about isomerization in alkanes. isomerization and reformation are processes in which straight-chain alkanes are heated in the presence of a platinum catalyst. in isomerization, the alkanes become branched-chain isomers. in other words, it does not lose any carbons or hydrogens, keeping the same molecular weight. in reformation, the alkanes become cycloalkanes or aromatic hydrocarbons, giving off hydrogen as a by-product. both of these processes raise the octane number of the substance. butane is the most common alkane that is put under the process of isomerization, as it makes many branched alkanes with high octane

numbers. other reactions alkanes will react with steam in the presence of a nickel catalyst to give hydrogen. alkanes can be chlorosulfonated and nitrated, although both reactions require special conditions. the fermentation of alkanes to carboxylic acids is of some technical importance. in the reed reaction, sulfur dioxide, chlorine and light convert hydrocarbons to sulfonyl chlorides. nucleophilic abstraction can be used to separate an alkane from a metal. alkyl groups can be transferred from one compound to another by transmetalation reactions. a mixture of antimony pentafluoride (sbf5) and fluorosulfonic acid (hso3f), called magic acid, can protonate alkanes. occurrence occurrence of alkanes in the universe alkanes form a small portion of the atmospheres of the outer gas planets such as jupiter (0.1%

methane, 2ppm ethane), saturn (0.2% methane, 5ppm ethane), uranus (1.99% methane, 2.5ppm ethane) and neptune (1.5% methane, 1.5ppm ethane). titan (1.6% methane), a satellite of saturn, was examined by the huygens probe, which indicated that titan's atmosphere periodically rains liquid methane onto the moon's surface. also on titan the cassini mission has imaged seasonal methane/ethane lakes near the polar regions of titan. methane and ethane have also been detected in the tail of the comet hyakutake. chemical analysis showed that the abundances of ethane and methane were roughly equal, which is thought to imply that its ices formed in interstellar space, away from the sun, which would have evaporated these volatile molecules. alkanes have also been detected in meteorites such as carbonaceous chondrites. occurrence

of alkanes on earth traces of methane gas (about 0.0002% or 1745ppb) occur in the earth's atmosphere, produced primarily by methanogenic microorganisms, such as archaea in the gut of ruminants. the most important commercial sources for alkanes are natural gas and oil. natural gas contains primarily methane and ethane, with some propane and butane: oil is a mixture of liquid alkanes and other hydrocarbons. these hydrocarbons were formed when marine animals and plants (zooplankton and phytoplankton) died and sank to the bottom of ancient seas and were covered with sediments in an anoxic environment and converted over many millions of years at high temperatures and high pressure to their current form. natural gas resulted thereby for example from the following reaction: c6h12o6 3ch4 + 3co2 these hydrocarbon deposits,

collected in porous rocks trapped beneath impermeable cap rocks, comprise commercial oil fields. they have formed over millions of years and once exhausted cannot be readily replaced. the depletion of these hydrocarbons reserves is the basis for what is known as the energy crisis. methane is also present in what is called biogas, produced by animals and decaying matter, which is a possible renewable energy source. alkanes have a low solubility in water, so the content in the oceans is negligible; however, at high pressures and low temperatures (such as at the bottom of the oceans), methane can co-crystallize with water to form a solid methane clathrate (methane hydrate). although this cannot be commercially exploited at the present time, the amount of combustible energy of the known methane clathrate fields

exceeds the energy content of all the natural gas and oil deposits put together. methane extracted from methane clathrate is, therefore, a candidate for future fuels. biological occurrence acyclic alkanes occur in nature in various ways. bacteria and archaea certain types of bacteria can metabolize alkanes: they prefer even-numbered carbon chains as they are easier to degrade than odd-numbered chains. on the other hand, certain archaea, the methanogens, produce large quantities of methane by the metabolism of carbon dioxide or other oxidized organic compounds. the energy is released by the oxidation of hydrogen: co2 + 4h2 ch4 + 2h2o methanogens are also the producers of marsh gas in wetlands. the methane output of cattle and other herbivores, which can release 30 to 50 gallons per day, and of termites,

is also due to methanogens. they also produce this simplest of all alkanes in the intestines of humans. methanogenic archaea are, hence, at the end of the carbon cycle, with carbon being released back into the atmosphere after having been fixed by photosynthesis. it is probable that our current deposits of natural gas were formed in a similar way. fungi and plants alkanes also play a role, if a minor role, in the biology of the three eukaryotic groups of organisms: fungi, plants and animals. some specialized yeasts, e.g., candida tropicale, pichia sp., rhodotorula sp., can use alkanes as a source of carbon or energy. the fungus amorphotheca resinae prefers the longer-chain alkanes in aviation fuel, and can cause serious problems for aircraft in tropical regions. in plants, the solid long-chain alkanes are found

in the plant cuticle and epicuticular wax of many species, but are only rarely major constituents. they protect the plant against water loss, prevent the leaching of important minerals by the rain, and protect against bacteria, fungi, and harmful insects. the carbon chains in plant alkanes are usually odd-numbered, between 27 and 33 carbon atoms in length and are made by the plants by decarboxylation of even-numbered fatty acids. the exact composition of the layer of wax is not only species-dependent but changes also with the season and such environmental factors as lighting conditions, temperature or humidity. more volatile short-chain alkanes are also produced by and found in plant tissues. the jeffrey pine is noted for producing exceptionally high levels of n-heptane in its resin, for which reason its distillate

was designated as the zero point for one octane rating. floral scents have also long been known to contain volatile alkane components, and n-nonane is a significant component in the scent of some roses. emission of gaseous and volatile alkanes such as ethane, pentane, and hexane by plants has also been documented at low levels, though they are not generally considered to be a major component of biogenic air pollution. edible vegetable oils also typically contain small fractions of biogenic alkanes with a wide spectrum of carbon numbers, mainly 8 to 35, usually peaking in the low to upper 20s, with concentrations up to dozens of milligrams per kilogram (parts per million by weight) and sometimes over a hundred for the total alkane fraction. animals alkanes are found in animal products, although they are less

important than unsaturated hydrocarbons. one example is the shark liver oil, which is approximately 14% pristane (2,6,10,14-tetramethylpentadecane, c19h40). they are important as pheromones, chemical messenger materials, on which insects depend for communication. in some species, e.g. the support beetle xylotrechus colonus, pentacosane (c25h52), 3-methylpentaicosane (c26h54) and 9-methylpentaicosane (c26h54) are transferred by body contact. with others like the tsetse fly glossina morsitans morsitans, the pheromone contains the four alkanes 2-methylheptadecane (c18h38), 17,21-dimethylheptatriacontane (c39h80), 15,19-dimethylheptatriacontane (c39h80) and 15,19,23-trimethylheptatriacontane (c40h82), and acts by smell over longer distances. waggle-dancing honey bees produce and release two alkanes, tricosane and

pentacosane. ecological relations one example, in which both plant and animal alkanes play a role, is the ecological relationship between the sand bee (andrena nigroaenea) and the early spider orchid (ophrys sphegodes); the latter is dependent for pollination on the former. sand bees use pheromones in order to identify a mate; in the case of a. nigroaenea, the females emit a mixture of tricosane (c23h48), pentacosane (c25h52) and heptacosane (c27h56) in the ratio 3:3:1, and males are attracted by specifically this odor. the orchid takes advantage of this mating arrangement to get the male bee to collect and disseminate its pollen; parts of its flower not only resemble the appearance of sand bees but also produce large quantities of the three alkanes in the same ratio as female sand bees. as a result, numerous

males are lured to the blooms and attempt to copulate with their imaginary partner: although this endeavor is not crowned with success for the bee, it allows the orchid to transfer its pollen, which will be dispersed after the departure of the frustrated male to other blooms. production petroleum refining as stated earlier, the most important source of alkanes is natural gas and crude oil. alkanes are separated in an oil refinery by fractional distillation and processed into many products. fischertropsch the fischertropsch process is a method to synthesize liquid hydrocarbons, including alkanes, from carbon monoxide and hydrogen. this method is used to produce substitutes for petroleum distillates. laboratory preparation there is usually little need for alkanes to be synthesized in the laboratory, since

they are usually commercially available. also, alkanes are generally unreactive chemically or biologically, and do not undergo functional group interconversions cleanly. when alkanes are produced in the laboratory, it is often a side-product of a reaction. for example, the use of n-butyllithium as a strong base gives the conjugate acid, n-butane as a side-product: c4h9li + h2o c4h10 + lioh however, at times it may be desirable to make a section of a molecule into an alkane-like functionality (alkyl group) using the above or similar methods. for example, an ethyl group is an alkyl group; when this is attached to a hydroxy group, it gives ethanol, which is not an alkane. to do so, the best-known methods are hydrogenation of alkenes: rch=ch2 + h2 rch2ch3(r = alkyl) alkanes or alkyl groups can also be prepared

directly from alkyl halides in the coreyhouseposnerwhitesides reaction. the bartonmccombie deoxygenation removes hydroxyl groups from alcohols e.g. and the clemmensen reduction removes carbonyl groups from aldehydes and ketones to form alkanes or alkyl-substituted compounds e.g.: preparation from other organic compounds alkanes can be prepared from a variety of organic compounds. these include alkenes, alkynes, haloalkanes, alcohols, aldehydes, ketones and carboxylic acids. from alkenes and alkynes addition of molecular hydrogen across the bond(s) of alkenes and alkynes give alkanes. this hydrogenation reaction is typically performed using a powdered metal catalyst, such as palladium, platinum, or nickel. the reaction is exothermic because the product alkane is more stable. this is an important process

in several fields of industrial and research chemistry. from haloalkanes several methods produce alkanes from haloalkanes. in the wurtz reaction, a haloalkane is treated with sodium in dry ether to yield an alkane having double the number of carbon atoms. this reaction proceeds through a free radical intermediate and has the possibility of alkene formation in case of tertiary haloalkanes and vicinal dihalides. 2 rx + 2 na rr + 2 na+x in coreyhouse synthesis, a haloalkane is treated with dialkyl lithium cuprate, a gilman reagent, to yield a higher alkane: li+[rcur] + r'x rr' + rcu + li+x haloalkanes can be reduced to alkanes by reaction with hydride reagents such as lithium aluminium hydride. rx + h rh + x applications the applications of alkanes depend on the number of carbon atoms. the first four

alkanes are used mainly for heating and cooking purposes, and in some countries for electricity generation. methane and ethane are the main components of natural gas; they are normally stored as gases under pressure. it is, however, easier to transport them as liquids: this requires both compression and cooling of the gas. propane and butane are gases at atmospheric pressure that can be liquefied at fairly low pressures and are commonly known as liquified petroleum gas (lpg). propane is used in propane gas burners and as a fuel for road vehicles, butane in space heaters and disposable cigarette lighters. both are used as propellants in aerosol sprays. from pentane to octane the alkanes are highly volatile liquids. they are used as fuels in internal combustion engines, as they vaporize easily on entry into the

combustion chamber without forming droplets, which would impair the uniformity of the combustion. branched-chain alkanes are preferred as they are much less prone to premature ignition, which causes knocking, than their straight-chain homologues. this propensity to premature ignition is measured by the octane rating of the fuel, where 2,2,4-trimethylpentane (isooctane) has an arbitrary value of 100, and heptane has a value of zero. apart from their use as fuels, the middle alkanes are also good solvents for nonpolar substances. alkanes from nonane to, for instance, hexadecane (an alkane with sixteen carbon atoms) are liquids of higher viscosity, less and less suitable for use in gasoline. they form instead the major part of diesel and aviation fuel. diesel fuels are characterized by their cetane number, cetane

being an old name for hexadecane. however, the higher melting points of these alkanes can cause problems at low temperatures and in polar regions, where the fuel becomes too thick to flow correctly. alkanes from hexadecane upwards form the most important components of fuel oil and lubricating oil. in the latter function, they work at the same time as anti-corrosive agents, as their hydrophobic nature means that water cannot reach the metal surface. many solid alkanes find use as paraffin wax, for example, in candles. this should not be confused however with true wax, which consists primarily of esters. alkanes with a chain length of approximately 35 or more carbon atoms are found in bitumen, used, for example, in road surfacing. however, the higher alkanes have little value and are usually split into lower

alkanes by cracking. some synthetic polymers such as polyethylene and polypropylene are alkanes with chains containing hundreds or thousands of carbon atoms. these materials are used in innumerable applications, and billions of kilograms of these materials are made and used each year. environmental transformations alkanes are chemically very inert apolar molecules which are not very reactive as organic compounds. this inertness yields serious ecological issues if they are released into the environment. due to their lack of functional groups and low water solubility, alkanes show poor bioavailability for microorganisms. there are, however, some microorganisms possessing the metabolic capacity to utilize n-alkanes as both carbon and energy sources. some bacterial species are highly specialised in degrading

alkanes; these are referred to as hydrocarbonoclastic bacteria. hazards methane is flammable, explosive and dangerous to inhale; because it is a colorless, odorless gas, special caution must be taken around methane. ethane is also extremely flammable, explosive, and dangerous to inhale. both of them may cause suffocation. propane, too, is flammable and explosive, and may cause drowsiness or unconsciousness if inhaled. butane presents the same hazards as propane. alkanes also pose a threat to the environment. branched alkanes have a lower biodegradability than unbranched alkanes. methane is considered to be the greenhouse gas that is most dangerous to the environment, although the amount of methane in the atmosphere is relatively low. see also alkene alkyne cycloalkane higher alkanes references further

united states appellate procedure involves the rules and regulations for filing appeals in state courts and federal courts. the nature of an appeal can vary greatly depending on the type of case and the rules of the court in the jurisdiction where the case was prosecuted. there are many types of standard of review for appeals, such as de novo and abuse of discretion. however, most appeals begin when a party files a petition for review to a higher court for the purpose of overturning the lower court's decision. an appellate court is a court that hears cases on appeal from another court. depending on the particular legal rules that apply to each circumstance, a party to a court case who is unhappy with the result might be able to challenge that result in an appellate court on specific grounds. these grounds typically

could include errors of law, fact, procedure or due process. in different jurisdictions, appellate courts are also called appeals courts, courts of appeals, superior courts, or supreme courts. the specific procedures for appealing, including even whether there is a right of appeal from a particular type of decision, can vary greatly from state to state. the right to file an appeal can also vary from state to state; for example, the new jersey constitution vests judicial power in a supreme court, a superior court, and other courts of limited jurisdiction, with an appellate court being part of the superior court. access to appellant status a party who files an appeal is called an "appellant", "plaintiff in error", "petitioner" or "pursuer", and a party on the other side is called an "appellee". a "cross-appeal"

is an appeal brought by the respondent. for example, suppose at trial the judge found for the plaintiff and ordered the defendant to pay $50,000. if the defendant files an appeal arguing that he should not have to pay any money, then the plaintiff might file a cross-appeal arguing that the defendant should have to pay $200,000 instead of $50,000. the appellant is the party who, having lost part or all their claim in a lower court decision, is appealing to a higher court to have their case reconsidered. this is usually done on the basis that the lower court judge erred in the application of law, but it may also be possible to appeal on the basis of court misconduct, or that a finding of fact was entirely unreasonable to make on the evidence. the appellant in the new case can be either the plaintiff (or claimant),

defendant, third-party intervenor, or respondent (appellee) from the lower case, depending on who was the losing party. the winning party from the lower court, however, is now the respondent. in unusual cases the appellant can be the victor in the court below, but still appeal. an appellee is the party to an appeal in which the lower court judgment was in its favor. the appellee is required to respond to the petition, oral arguments, and legal briefs of the appellant. in general, the appellee takes the procedural posture that the lower court's decision should be affirmed. ability to appeal an appeal "as of right" is one that is guaranteed by statute or some underlying constitutional or legal principle. the appellate court cannot refuse to listen to the appeal. an appeal "by leave" or "permission" requires the

appellant to obtain leave to appeal; in such a situation either or both of the lower court and the court may have the discretion to grant or refuse the appellant's demand to appeal the lower court's decision. in the supreme court, review in most cases is available only if the court exercises its discretion and grants a writ of certiorari. in tort, equity, or other civil matters either party to a previous case may file an appeal. in criminal matters, however, the state or prosecution generally has no appeal "as of right". and due to the double jeopardy principle, the state or prosecution may never appeal a jury or bench verdict of acquittal. but in some jurisdictions, the state or prosecution may appeal "as of right" from a trial court's dismissal of an indictment in whole or in part or from a trial court's granting

of a defendant's suppression motion. likewise, in some jurisdictions, the state or prosecution may appeal an issue of law "by leave" from the trial court or the appellate court. the ability of the prosecution to appeal a decision in favor of a defendant varies significantly internationally. all parties must present grounds to appeal, or it will not be heard. by convention in some law reports, the appellant is named first. this can mean that where it is the defendant who appeals, the name of the case in the law reports reverses (in some cases twice) as the appeals work their way up the court hierarchy. this is not always true, however. in the federal courts, the parties' names always stay in the same order as the lower court when an appeal is taken to the circuit courts of appeals, and are re-ordered only if

the appeal reaches the supreme court. direct or collateral: appealing criminal convictions many jurisdictions recognize two types of appeals, particularly in the criminal context. the first is the traditional "direct" appeal in which the appellant files an appeal with the next higher court of review. the second is the collateral appeal or post-conviction petition, in which the petitioner-appellant files the appeal in a court of first instanceusually the court that tried the case. the key distinguishing factor between direct and collateral appeals is that the former occurs in state courts, and the latter in federal courts. relief in post-conviction is rare and is most often found in capital or violent felony cases. the typical scenario involves an incarcerated defendant locating dna evidence demonstrating the

defendant's actual innocence. appellate review "appellate review" is the general term for the process by which courts with appellate jurisdiction take jurisdiction of matters decided by lower courts. it is distinguished from judicial review, which refers to the court's overriding constitutional or statutory right to determine if a legislative act or administrative decision is defective for jurisdictional or other reasons (which may vary by jurisdiction). in most jurisdictions the normal and preferred way of seeking appellate review is by filing an appeal of the final judgment. generally, an appeal of the judgment will also allow appeal of all other orders or rulings made by the trial court in the course of the case. this is because such orders cannot be appealed "as of right". however, certain critical interlocutory

court orders, such as the denial of a request for an interim injunction, or an order holding a person in contempt of court, can be appealed immediately although the case may otherwise not have been fully disposed of. there are two distinct forms of appellate review, "direct" and "collateral". for example, a criminal defendant may be convicted in state court, and lose on "direct appeal" to higher state appellate courts, and if unsuccessful, mount a "collateral" action such as filing for a writ of habeas corpus in the federal courts. generally speaking, "[d]irect appeal statutes afford defendants the opportunity to challenge the merits of a judgment and allege errors of law or fact. ... [collateral review], on the other hand, provide[s] an independent and civil inquiry into the validity of a conviction and sentence,

and as such are generally limited to challenges to constitutional, jurisdictional, or other fundamental violations that occurred at trial." "graham v. borgen", 483 f 3d. 475 (7th cir. 2007) (no. 044103) (slip op. at 7) (citation omitted). in anglo-american common law courts, appellate review of lower court decisions may also be obtained by filing a petition for review by prerogative writ in certain cases. there is no corresponding right to a writ in any pure or continental civil law legal systems, though some mixed systems such as quebec recognize these prerogative writs. direct appeal after exhausting the first appeal as of right, defendants usually petition the highest state court to review the decision. this appeal is known as a direct appeal. the highest state court, generally known as the supreme court,

exercises discretion over whether it will review the case. on direct appeal, a prisoner challenges the grounds of the conviction based on an error that occurred at trial or some other stage in the adjudicative process. preservation issues an appellant's claim(s) must usually be preserved at trial. this means that the defendant had to object to the error when it occurred in the trial. because constitutional claims are of great magnitude, appellate courts might be more lenient to review the claim even if it was not preserved. for example, connecticut applies the following standard to review unpreserved claims: 1.the record is adequate to review the alleged claim of error; 2. the claim is of constitutional magnitude alleging the violation of a fundamental right; 3. the alleged constitutional violation clearly exists

and clearly deprived the defendant of a fair trial; 4. if subject to harmless error analysis, the state has failed to demonstrate harmlessness of the alleged constitutional violation beyond a reasonable doubt. state post-conviction relief: collateral appeal all states have a post-conviction relief process. similar to federal post-conviction relief, an appellant can petition the court to correct alleged fundamental errors that were not corrected on direct review. typical claims might include ineffective assistance of counsel and actual innocence based on new evidence. these proceedings are normally separate from the direct appeal, however some states allow for collateral relief to be sought on direct appeal. after direct appeal, the conviction is considered final. an appeal from the post conviction court proceeds

just as a direct appeal. that is, it goes to the intermediate appellate court, followed by the highest court. if the petition is granted the appellant could be released from incarceration, the sentence could be modified, or a new trial could be ordered. habeas corpus notice of appeal a "notice of appeal" is a form or document that in many cases is required to begin an appeal. the form is completed by the appellant or by the appellant's legal representative. the nature of this form can vary greatly from country to country and from court to court within a country. the specific rules of the legal system will dictate exactly how the appeal is officially begun. for example, the appellant might have to file the notice of appeal with the appellate court, or with the court from which the appeal is taken, or both. some

courts have samples of a notice of appeal on the court's own web site. in new jersey, for example, the administrative office of the court has promulgated a form of notice of appeal for use by appellants, though using this exact form is not mandatory and the failure to use it is not a jurisdictional defect provided that all pertinent information is set forth in whatever form of notice of appeal is used. the deadline for beginning an appeal can often be very short: traditionally, it is measured in days, not months. this can vary from country to country, as well as within a country, depending on the specific rules in force. in the u.s. federal court system, criminal defendants must file a notice of appeal within 10 days of the entry of either the judgment or the order being appealed, or the right to appeal is forfeited. appellate

procedure generally speaking the appellate court examines the record of evidence presented in the trial court and the law that the lower court applied and decides whether that decision was legally sound or not. the appellate court will typically be deferential to the lower court's findings of fact (such as whether a defendant committed a particular act), unless clearly erroneous, and so will focus on the court's application of the law to those facts (such as whether the act found by the court to have occurred fits a legal definition at issue). if the appellate court finds no defect, it "affirms" the judgment. if the appellate court does find a legal defect in the decision "below" (i.e., in the lower court), it may "modify" the ruling to correct the defect, or it may nullify ("reverse" or "vacate") the whole

decision or any part of it. it may, in addition, send the case back ("remand" or "remit") to the lower court for further proceedings to remedy the defect. in some cases, an appellate court may review a lower court decision "de novo" (or completely), challenging even the lower court's findings of fact. this might be the proper standard of review, for example, if the lower court resolved the case by granting a pre-trial motion to dismiss or motion for summary judgment which is usually based only upon written submissions to the trial court and not on any trial testimony. another situation is where appeal is by way of "re-hearing". certain jurisdictions permit certain appeals to cause the trial to be heard afresh in the appellate court. sometimes, the appellate court finds a defect in the procedure the parties

used in filing the appeal and dismisses the appeal without considering its merits, which has the same effect as affirming the judgment below. (this would happen, for example, if the appellant waited too long, under the appellate court's rules, to file the appeal.) generally, there is no trial in an appellate court, only consideration of the record of the evidence presented to the trial court and all the pre-trial and trial court proceedings are reviewedunless the appeal is by way of re-hearing, new evidence will usually only be considered on appeal in "very" rare instances, for example if that material evidence was unavailable to a party for some very significant reason such as prosecutorial misconduct. in some systems, an appellate court will only consider the written decision of the lower court, together

with any written evidence that was before that court and is relevant to the appeal. in other systems, the appellate court will normally consider the record of the lower court. in those cases the record will first be certified by the lower court. the appellant has the opportunity to present arguments for the granting of the appeal and the appellee (or respondent) can present arguments against it. arguments of the parties to the appeal are presented through their appellate lawyers, if represented, or "pro se" if the party has not engaged legal representation. those arguments are presented in written briefs and sometimes in oral argument to the court at a hearing. at such hearings each party is allowed a brief presentation at which the appellate judges ask questions based on their review of the record below and

the submitted briefs. in an adversarial system, appellate courts do not have the power to review lower court decisions unless a party appeals it. therefore, if a lower court has ruled in an improper manner, or against legal precedent, that judgment will stand if not appealed even if it might have been overturned on appeal. the united states legal system generally recognizes two types of appeals: a trial "de novo" or an appeal on the record. a trial de novo is usually available for review of informal proceedings conducted by some minor judicial tribunals in proceedings that do not provide all the procedural attributes of a formal judicial trial. if unchallenged, these decisions have the power to settle more minor legal disputes once and for all. if a party is dissatisfied with the finding of such a tribunal,

one generally has the power to request a trial "de novo" by a court of record. in such a proceeding, all issues and evidence may be developed newly, as though never heard before, and one is not restricted to the evidence heard in the lower proceeding. sometimes, however, the decision of the lower proceeding is itself admissible as evidence, thus helping to curb frivolous appeals. in some cases, an application for "trial de novo" effectively erases the prior trial as if it had never taken place. the supreme court of virginia has stated that '"this court has repeatedly held that the effect of an appeal to circuit court is to "annul the judgment of the inferior tribunal as completely as if there had been no previous trial."' the only exception to this is that if a defendant appeals a conviction for a crime having

multiple levels of offenses, where they are convicted on a lesser offense, the appeal is of the lesser offense; the conviction represents an acquittal of the more serious offenses. "[a] trial on the same charges in the circuit court does not violate double jeopardy principles, . . . subject only to the limitation that conviction in [the] district court for an offense lesser included in the one charged constitutes an acquittal of the greater offense, permitting trial de novo in the circuit court only for the lesser-included offense." in an appeal on the record from a decision in a judicial proceeding, both appellant and respondent are bound to base their arguments wholly on the proceedings and body of evidence as they were presented in the lower tribunal. each seeks to prove to the higher court that the result

they desired was the just result. precedent and case law figure prominently in the arguments. in order for the appeal to succeed, the appellant must prove that the lower court committed reversible error, that is, an impermissible action by the court acted to cause a result that was unjust, and which would not have resulted had the court acted properly. some examples of reversible error would be erroneously instructing the jury on the law applicable to the case, permitting seriously improper argument by an attorney, admitting or excluding evidence improperly, acting outside the court's jurisdiction, injecting bias into the proceeding or appearing to do so, juror misconduct, etc. the failure to formally object at the time, to what one views as improper action in the lower court, may result in the affirmance of

the lower court's judgment on the grounds that one did not "preserve the issue for appeal" by objecting. in cases where a judge rather than a jury decided issues of fact, an appellate court will apply an "abuse of discretion" standard of review. under this standard, the appellate court gives deference to the lower court's view of the evidence, and reverses its decision only if it were a clear abuse of discretion. this is usually defined as a decision outside the bounds of reasonableness. on the other hand, the appellate court normally gives less deference to a lower court's decision on issues of law, and may reverse if it finds that the lower court applied the wrong legal standard. in some cases, an appellant may successfully argue that the law under which the lower decision was rendered was unconstitutional

or otherwise invalid, or may convince the higher court to order a new trial on the basis that evidence earlier sought was concealed or only recently discovered. in the case of new evidence, there must be a high probability that its presence or absence would have made a material difference in the trial. another issue suitable for appeal in criminal cases is effective assistance of counsel. if a defendant has been convicted and can prove that his lawyer did not adequately handle his case and that there is a reasonable probability that the result of the trial would have been different had the lawyer given competent representation, he is entitled to a new trial. a lawyer traditionally starts an oral argument to any appellate court with the words "may it please the court." after an appeal is heard, the "mandate"

is a formal notice of a decision by a court of appeal; this notice is transmitted to the trial court and, when filed by the clerk of the trial court, constitutes the final judgment on the case, unless the appeal court has directed further proceedings in the trial court. the mandate is distinguished from the appeal court's opinion, which sets out the legal reasoning for its decision. in some jurisdictions the mandate is known as the "remittitur". results the result of an appeal can be: affirmed: where the reviewing court basically agrees with the result of the lower courts' ruling(s). reversed: where the reviewing court basically disagrees with the result of the lower courts' ruling(s), and overturns their decision. vacated: where the reviewing court overturns the lower courts' ruling(s) as invalid, without

necessarily disagreeing with it/them, e.g. because the case was decided on the basis of a legal principle that no longer applies. remanded: where the reviewing court sends the case back to the lower court. there can be multiple outcomes, so that the reviewing court can affirm some rulings, reverse others and remand the case all at the same time. remand is not required where there is nothing left to do in the case. "generally speaking, an appellate court's judgment provides 'the final directive of the appeals courts as to the matter appealed, setting out with specificity the court's determination that the action appealed from should be affirmed, reversed, remanded or modified'". some reviewing courts who have discretionary review may send a case back without comment other than review improvidently granted. in

other words, after looking at the case, they chose not to say anything. the result for the case of review improvidently granted is effectively the same as affirmed, but without that extra higher court stamp of approval. see also appellate court appellee civil procedure court of appeals courts-martial in the united states criminal procedure defendant en banc interlocutory appeal list of legal topics list of wrongful convictions in the united states petition for stay plaintiff pursuer reversible error supreme court of the united states writ of certiorari writ of habeas corpus writ of mandamus references external links legal procedure united states procedural law

in law, an answer was originally a solemn assertion in opposition to someone or something, and thus generally any counter-statement or defense, a reply to a question or response, or objection, or a correct solution of a problem. in the common law, an answer is the first pleading by a defendant, usually filed and served upon the plaintiff within a certain strict time limit after a civil complaint or criminal information or indictment has been served upon the defendant. it may have been preceded by an optional "pre-answer" motion to dismiss or demurrer; if such a motion is unsuccessful, the defendant must file an answer to the complaint or risk an adverse default judgment. in a criminal case, there is usually an arraignment or some other kind of appearance before the defendant comes to court. the pleading in the