Chapter 10. Organic Chemistry

# 10.5 Nomenclature of Amines

### Learning Objectives

By the end of this section, you will be able to:
• Describe the structure and properties of an amine.
• Distinguish between a primary, secondary and tertiary amine.
• Name and draw structures for primary, secondary and tertiary amines.

An amine is an organic derivative of ammonia (NH3). In amines, one or more of the H atoms in NH3 is substituted with an organic group.

 A primary amine has one H atom substituted with an R group: A secondary amine has two H atoms substituted with an R group: A tertiary amine has all three H atoms substituted with R groups:

Like ammonia, amines are weak bases due to the lone pair of electrons on their nitrogen atoms:

The basicity of an amine’s nitrogen atom plays an important role in much of the compound’s chemistry.

## Naming Amines

The alkyl groups connected to the nitrogen atom are named separately and followed by “amine.”  If some alkyl groups are the same, then a prefix is used (di or tri), as illustrated here for a few simple examples:

### Example 1

Name the following organic compounds:

a) (CH3)2NCH2CH3    b) CH3CH2CH2NHCH3   c) CH3(CH3CH2)NCH2CH2CH3

Solution
a) ethyldimethylamine    b) methylpropylamine   c) ethylmethylpropylamine

Test Yourself
Give the condensed structure of the following amines:

a) butylamine   b) trihexylamine   c) methylpentylamine

a) CH3CH2CH2CH2NH2    b) (CH3CH2CH2CH2CH2CH2)3N   c) CH3(CH3CH2CH2CH2CH2)NH

## Key Concepts and Summary

Compounds containing a nitrogen atom bonded in a hydrocarbon framework are classified as amines. Amines are a basic functional group. An acid-base reaction occurs when an amine is mixed with and an acid.

The systematic methods of naming amines follow a simple procedure:
primary amines: ALKYLamine
secondary amines: ALKYLALKYLamine    or   diALKYLamine
tertiary amines: ALKYLALKYLALKYLamine    or   triALKYLamine

### Exercises

1. What are the structure and name of the smallest amine?

2. Identify each compound as a primary, secondary, or tertiary amine.

a)

b)

c)

3. Identify each compound as a primary, secondary, or tertiary amine.

a)

b)

4. Write the chemical reaction between each amine in Exercise 2 and HCl.

5. Name each amine.

a)      b)

c)    d)

1. CH3NH2; methylamine

2. a)  primary  b)  tertiary  c)  secondary

3. a) primary  b) secondary

4. a)  C3H3CO2HSHNH2 + HCl $\longrightarrow$ C3H3CO2HSHNH3Cl

b)  (C6H11)(C2H5)(CH3)N + HCl $\longrightarrow$ (C6H11)(C2H5)(CH3)NHCl

c)  (C2H5)(CH3)NH + HCl $\longrightarrow$ (C2H5)(CH3)NH2Cl

5. a)  ethylmethylamine   b)  ethyldipropylamine  c) diethylmethylamine

## Glossary

amine: organic molecule in which a nitrogen atom is bonded to one or more alkyl group