In organic chemistry, an alkyl group is an

alkane 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 ...

missing one hydrogen. The term ''alkyl'' is intentionally unspecific to include many possible substitutions. An acyclic alkyl has the general formula of . A cycloalkyl is derived from a

cycloalkane In organic chemistry, the cycloalkanes (also called naphthenes, but distinct from naphthalene) are the monocyclic saturated hydrocarbons. In other words, a cycloalkane consists only of hydrogen and carbon atoms arranged in a structure containing ...

by removal of a hydrogen atom from a ring and has the general formula . Typically an alkyl is a part of a larger molecule. In

structural formula The structural formula of a chemical compound is a graphic representation of the molecular structure (determined by structural chemistry methods), showing how the atoms are possibly arranged in the real three-dimensional space. The chemical bondi ...

e, the symbol R is used to designate a generic (unspecified) alkyl group. The smallest alkyl group is

methyl In organic chemistry, a methyl group is an alkyl derived from methane, containing one carbon atom bonded to three hydrogen atoms, having chemical formula . In formulas, the group is often abbreviated as Me. This hydrocarbon group occurs in many ...

, with the formula .

Related concepts

Alkylation is an important operation in refineries, for example in the production of high-octane gasoline. Alkylating antineoplastic agents are a class of compounds that are used to treat cancer. In such case, the term alkyl is used loosely. For example,

nitrogen mustard Nitrogen mustards are cytotoxic organic compounds with the chloroethylamine (Cl(CH2)2NR2) functional group. Although originally produced as chemical warfare agents, they were the first chemotherapeutic agents for treatment of cancer. Nitrogen m ...

s are well-known alkylating agents, but they are not simple hydrocarbons. In chemistry, alkyl is a group, a substituent, that is attached to other molecular fragments. For example, alkyl lithium reagents have the empirical formula Li(alkyl), where alkyl = methyl, ethyl, etc. A ''dialkyl'' ether is an ether with two alkyl groups, e.g., diethyl ether (O(C₂H₅)₂).

In medicinal chemistry

In medicinal chemistry, the incorporation of alkyl chains into some chemical compounds increases their lipophilicity. This strategy has been used to increase the antimicrobial activity of flavanones and

chalcone Chalcone is the organic compound C6H5C(O)CH=CHC6H5. It is an α,β-unsaturated ketone. A variety of important biological compounds are known collectively as chalcones or chalconoids. Chemical properties Chalcones have two absorption maxima a ...

Alkyl cations, anions, and radicals

Usually, alkyl groups are attached to other atoms or groups of atoms. Free alkyls occur as neutral compounds, as anions, or as cations. The cations are called

carbocation A carbocation is an ion with a positively charged carbon atom. Among the simplest examples are the methenium , methanium and vinyl cations. Occasionally, carbocations that bear more than one positively charged carbon atom are also encountere ...

s. The anions are called

carbanion In organic chemistry, a carbanion is an anion in which carbon is trivalent (forms three bonds) and bears a formal negative charge (in at least one significant resonance form). Formally, a carbanion is the conjugate base of a carbon acid: :R3C ...

s. The neutral alkyl free radicals have no special name. Such species are usually encountered only as transient intermediates, but some are quite stable and can be "put into a bottle". Typically alkyl cations are generated using super acids, alkyl anions are observed in the presence of strong bases, and alkyl radicals are generated by a photochemical reaction. Alkyls are commonly observed in

mass spectrometry Mass spectrometry (MS) is an analytical technique that is used to measure the mass-to-charge ratio of ions. The results are presented as a ''mass spectrum'', a plot of intensity as a function of the mass-to-charge ratio. Mass spectrometry is use ...

of organic compounds.

Nomenclature

Alkyls form

homologous series In organic chemistry, a homologous series is a sequence of compounds with the same functional group and similar chemical properties in which the members of the series can be branched or unbranched, or differ by molecular formula of and molecu ...

. The simplest series have the general formula C_''n''H_2''n''+1. Alkyls include ''

'', (CH₃·), ''

ethyl Ethyl may refer to: Arts and entertainment * Cold Ethyl, a Swedish rock band *Ethyl Sinclair, a character in the ''Dinosaurs'' television show Science and technology * Ethyl group, an organic chemistry moiety * Ethyl alcohol (or ethanol) * E ...

'' (C₂H₅·), '' propyl'' (C₃H₇·), '' butyl'' (C₄H₉·), '' pentyl'' (C₅H₁₁·), and so on. Alkyl groups that contain one ring have the formula C_''n''H_2''n''−1, e.g. cyclopropyl and cyclohexyl. The naming convention is taken from IUPAC nomenclature: These names are used to name branched chained structures, for example 3-methylpentane: The structure of 3-methylpentane is viewed as consisting of two parts. First, five atoms comprise the longest straight chain of carbon centers. The parent five-carbon compound is named

pentane Pentane is an organic compound with the formula C5H12—that is, an alkane with five carbon atoms. The term may refer to any of three structural isomers, or to a mixture of them: in the IUPAC nomenclature, however, pentane means exclusively the ' ...

(highlighted blue). The methyl "substituent" or "group" is highlighted red. According to the usual rules of nomenclature, alkyl groups are included in the name of the molecule before the root, as in

methylpentane Methylpentane may refer to: * 2-Methylpentane * 3-Methylpentane You could also have been looking for: * Methylpentenone {{Short pages monitor