Amines

Amines play a vital role in medicinal chemistry. As our body is having a lot of amino acids, these amines help in the regulation of our body. It is also believed that, vitamins were named keeping vital-amines in mind (though many vitamins don't have nitrogen at all). Similarly to produce several synthetic dyes, pigments the amines are used. Therefore, the amines are very important in our everyday life. 

Structure of Amines

Amines are the alkyl (or) aryl derivatives of NH₃.

The general formula of amine is R₃N, where R is an alkyl (or) aryl group or hydrogen In amines one or more Hydrogen atoms of ammonia are replaced by Alkyl or aryl groups. Here nitrogen atom of amines is like that of NH₃, it is sp³ hybridised. The three Alkyl groups (or hydrogen atoms) occupy corners of a tetrahedron, one of sp³ orbital occupying the unshared electron pair directed towards the other corner. We say shape of amine as “Trigonal Pyramidal”.                                            

Amines are classified as primary, secondary (or) tertiary according to the number of groups attached to the nitrogen atom. If one alkyl group has replaced one hydrogen atom of ammonia, it is primary amine (amine group or amine functional group of primary amine is – NH₂). Similarly, if two hydrogens are replaced, it is secondary amine and if all the three are replaced, it is tertiary amine (e.g trimethyl amine). 

NH₃            RNH₂         R₂NH             R₃N

 Ammonia    1^O Amine      2^o Amine        3^o Amine

Nomenclature of Amines

Nomenclature of amines is quite simple. Aliphatic amines are named by naming the alkyl group (or) groups attached to nitrogen , and following that by the word amine for example alkyl amine (methyl amine, ethyl amine) & benzyl amine.

More complicated amines are often named as prefixing amino - (or-N-methylamino -, N-N, diethyl  amino -, etc) to the name of the parent chain.

Aromatic amines - those in which nitrogen is attached to an aromatic ring - are generally named as derivatives of the simplest aromatic amine, aniline.

Salts of amines are generally named by replacing - amine by - ammonium (or - aniline by - anilinium), and adding the name of the anion.

Physical Properties of Amine

Amines are moderately polar substances; they have boiling points that are higher than those of alkanes but generally lower than alcohols of comparable molecular weight. Molecules of primary and secondary amines can form strong hydrogen bonds to each other and to water. Molecules of tertiary amines can not form hydrogen bonds to each other, but they can form hydrogen bonds to molecules of water or other hydroxylic solvents. As a result, tertiary amines generally boil at lower temperatures than primary and secondary amines of comparable molecular weight. Therefore, the order of boiling points of isomeric amines is as follows.

Primary > Secondary > Tertiary

Boiling points of amines, alcohols and alkanes of almost the same.

Related Resources

 We will have a detail discussion about amines in this unit under following subtopics

• Basicity of Amines

• Preparation of amines

• Chemical Properties of Amine

• Nitro & Cyno Compounds

• Solved Examples

Refer the below mentioned links to get an immediate solution to all queries on Organic chemistry:

JEE Organic Chemistry Syllabus

Reference books of Organic Chemistry

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