Amines

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The most important of the organic compounds showing appreciable basicity.

The amines are the organic bases.

Nomenclature

• Aliphatic amines are named by naming the alkyl group followed by the word -amine.

• Complicated amines are named by prefixing amino- to the name of the parent chain.

• Aromatic amines are named as derivative of the simplest aromatic amine, aniline.

• Salts of amines are named by replacing -amine by -ammonium (or -aniline by -anilinium).

Physical Properties

• Polar compounds

• Form intermolecular hydrogen bonds

• Higher boiling points than nonpolar compounds

• Lower boiling points than alcohols or carboxylic acids

• Quite soluble in water

• Methyl amines & ethyl amines smell like ammonia

• Higher alkyl amines have a “fishy” smell

• Aromatic amines are generally very toxic; they are absorbed through the skin, often with fatal results

• Aromatic amines are oxidized by air

Stereochemistry of Nitrogen

• Nitrogen uses sp³ hybridized orbitals

• Tetrahedral shape

– one orbital is a pair of nonbonding electrons

– the three remaining orbitals overlap s orbitals of hydrogen or carbon

• Approximate bond angles of 109^o

• Quaternary ammonium salts use all four sp³ orbitals to form bonds

Hofmann Degradation of Amines

When a primary aromatic amine, dissolved or suspended in cold aqueous mineral acid,

is treated with sodium nitrite, a diazonium salt is formed.