In organic chemistry, an alkyl group is an alkane missing one hydrogen. The term alkyl is intentionally unspecific to include many possible substitutions. An acyclic alkyl has the general formula of . A cycloalkyl group is derived from a cycloalkane 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 formulae, the symbol R is used to designate a generic (unspecified) alkyl group. The smallest alkyl group is methyl, with the formula .Virtual Textbook of Organic Chemistry Naming Organic Compounds
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, 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 .
The naming convention is taken from IUPAC nomenclature:
The prefixes taken from IUPAC nomenclature are used to name branched chained structures by their substituent groups, 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 (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. This name is, however, ambiguous, as the methyl branch could be on various carbon atoms. Thus, the name is 3-methylpentane to avoid ambiguity: The 3- is because the methyl is attached to the third of the five carbon atoms.
If there is more than one of the same alkyl group attached to a chain, then the prefixes are used on the alkyl groups to indicate multiples (i.e., di, tri, tetra, etc.)
This compound is known as 2,3,3-trimethylpentane. Here three identical alkyl groups attached to carbon atoms 2, 3, and 3. The numbers are included in the name to avoid ambiguity about the position of the groups, and "tri" indicates that there are three identical methyl groups. If one of the methyl groups attached to the third carbon atom were instead an ethyl group, then the name would be 3-ethyl-2,3-dimethylpentane. When there are different alkyl groups, they are listed in alphabetical order.
In addition, each position on an alkyl chain can be described according to how many other carbon atoms are attached to it. The terms primary carbon, secondary carbon, tertiary carbon, and quaternary refer to a carbon attached to one, two, three, or four other carbons respectively.
Methyl group | Ме | methyl | ||||
Ethyl group | Et | ethyl | ||||
propyl, n-propyl | Pr, nPr, n-Pr | propyl | ||||
isopropyl | iPr, i-Pr, iPr | 2-propyl | ||||
n-butyl | Bu, n-Bu, nBu | butyl | ||||
isobutyl | iBu, i-Bu, iBu | 2-methylpropyl | ||||
sec-butyl | sBu, s-Bu, sBu | 2-butyl | ||||
tert-butyl | tBu, t-Bu, tBu | tert-butyl | ||||
n-pentyl, amyl | Pe, Am, nPe, n-Pe, nPe, nAm | pentyl | ||||
tert-pentyl | tPe, t-Pe, tPe | No longer recommended | 2-methylbutan-2-yl (aka 1,1-dimethylpropyl) | |||
neopentyl | No longer recommended | 2,2-dimethylpropyl | ||||
isopentyl, isoamyl | No longer recommended | 3-methylbutyl | ||||
sec-pentyl | sPe, s-Pe, sPe | pentan-2-yl(or (1-Methylbutyl)) | ||||
3-pentyl | pentan-3-yl (also known as (1-Ethylpropyl)) | |||||
sec-isopentyl, sec-isoamyl, siamyl | Sia | 3-methylbutan-2-yl (or (1,2-Dimethylpropyl)) | ||||
active pentyl | 2-methylbutyl |
|
|