Alkyl

An Alkyl is a univalent radical containing only carbon and hydrogen atoms arranged in a chain. The alkyls form a homologous series with the general formula CnH2n+1. Examples include methyl, CH3· (derived from methane) and butyl C4H9· (derived from butane). They are normally not found on their own but are found as part of larger branched chain organic molecules. On their own they are free radicals and therefore extremely reactive.

Naming Alkyls

The naming convention for alkyls is much the same as alkanes. The suffix is always -yl. The prefix depends on how many carbon atoms are in the molecule. This uses the same system as for Alkanes as shown in this table (taken from IUPAC nomenclature):

Related Topics:
Alkanes - IUPAC nomenclature

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

For example, the first three alkyls are called Methyl, Ethyl and Propyl.

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

These names are used to name branched chained structures, for example 3-MethylPentane:

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

The structure of 3-MethylPentane is made of two parts. First, the longest straight chain of Carbon atoms; 5 Carbons long with no unsaturated bonds, thus named Pentane (Highlighted Blue). Second, there is an Alkyl group; Methyl (Highlighted Red). Alkyl groups are included in the name of a molecule before anything else. Thus the name becomes MethylPentane. This name is, however, ambiguous, as the Methyl branch could be on any one of three different carbon atoms (Second, Third or Fourth, from left to right). Thus the name becomes 3-MethylPentane to avoid ambiguation.

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

If there is more than one of the same Alkyl group attached to a chain, then the name becomes slightly different, for example 2,3,3-triMethylPentane:

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Here there are three identical alkyl groups attached to carbon atoms 2, 3 and 3. There name includes 2,3,3 to avoid ambiguation on the position of the groups and 'tri' to indicate that there are three identical alkyl groups, in this case they are all methyls. Suppose the methyl attached to carbon atom no.2 was, in fact, an Ethyl. The name would become 2-Ethyl-3,3-diMethylPentane. Note that when there are different alkyl groups, they are listed in alphabetical order.

~ ~ ~ ~ ~ ~ ~ ~ ~ ~