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Alkyl

What is an alkyl group?

Alkyl group is formed by removing a hydrogen atom from the molecule of alkane. Alkanes are quite often represented as R-H and here R stands for alkyl group.

The general formula of the alkyl group is CnH2n+1. The smallest alkyl group is CH3 called methyl.

A cycloalkyl is derived from a cycloalkane by removal of a hydrogen atom from a ring. The general formula of cycloalkyl is CnH2n-1.

Table of Contents

Nomenclature of alkyl groups

An alkyl group is named by replacing the suffix “ane” of the alkane with the suffix – “yl”.

Example:

CH4 – H → CH3

(Methane) (Methyl)

Number of carbon atom

Word Root

Name of alkyl group

Structure of alkyl group

1

C1

Meth

Methyl

CH3

2

C2

Eth

Ethyi

CH3-CH2

3

C3

Prop

Propyl

CH3-CH2-CH2

4

C4

But

Butyl

CH3-CH2-CH2-CH2

5

C5

Pent

Pentyl

CH3-CH2-CH2-CH2-CH2

6

C6

Hex

Hexyl

CH3-CH2-CH2-CH2-CH2-CH2

7

C7

Hept

Heptyl

CH3-CH2-CH2-CH2-CH2-CH2-CH2

8

C8

Oct

Octyl

CH3-CH2-CH2-CH2-CH2-CH2-CH2-CH2

9

C9

Non

Nonyl

CH3-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH2

10

C10

Dec

Decyl

CH3-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH2

Formation of alkyl groups

Alkyl group is formed by removing a hydrogen atom from the molecules of alkane. It may be noted that an alkane molecule can lead to more than one alkyl group depending upon the nature of the carbon atoms from which hydrogen is to be removed. For example,

(1) In ethane (C2H6), both the carbon atoms are primary so only one alkyl group can be formed.

(2) In Propane (C3H8), there are two types of carbon atoms present therefore, two different alkyl groups can be formed.

  • The secondary propyl group is called isopropyl group.

(3) n-Butane has also two types of carbon atoms that give two alkyl groups.

(4) Iso-Butane has primary and tertiary carbon so it gives the following alkyl groups.

  • The tertiary butyl group is also called neo butyl group.

Alkyl groups are attached to other atoms or groups of atoms. Free alkyls occur as neutral compounds, as anions, or as cations. Such species are usually encountered only as transient intermediates, but some are quite stable.

Alkyl cations

In the alkyl carbocation the carbon atom contains six electrons in the valence shell to form a positively charged species. Depending upon the nature of carbon atoms these are classified into three types primary, secondary and tertiary carbocation.

Alkyl anions

In the alkyl anion or carbanion, the carbon atom containing eight electrons in the valence shell form a negatively charged species. These are

Alkyl radical

In the alkyl free radical carbon contains seven electrons in the valence shell. Depending upon the nature of carbon atoms bearing unpaired electrons, alkyl free radical is classified as primary, secondary or tertiary in nature. Examples are:

Frequently Asked Questions on Alkyl

What do you mean by alkyl?

Alkyl is the functional group which is formed by removing a hydrogen atom from the molecules of alkane

What is the formula of an alkyl group?

The formula of the alkyl group is CnH2n+1.

What is the formula of the methyl group?

The formula of methyl group is CH3

What is an alkane formula?

The formula of alkane is CnH2n+2

What is alkyl free radical?

In the alkyl free radical carbon contains seven electrons in the valence shell. It is a neutral electron deficiency species.

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