Amines

Amines are the organic derivatives of ammonia, in which one, two or three hydrogens of NH3 are replaced by alkyl or aryl groups - giving primary (R-NH2), secondary (R2NH) and tertiary (R3N) amines. They are the most important nitrogen-containing organic bases, found in proteins, vitamins, hormones, alkaloids and a huge range of drugs and dyes. This chapter, worth a reliable 7-10 Board marks and 4-5 JEE/NEET questions a year, builds the chemistry of the C-N bond and the lone pair on nitrogen. We classify and name amines; study how they are prepared (by ammonolysis of alkyl halides, reduction of nitro compounds, nitriles and amides, the Gabriel phthalimide synthesis for pure primary amines, and the Hofmann bromamide degradation that shortens the chain by one carbon); explain their physical properties through hydrogen bonding; and analyse their basicity - the order of basic strength in the gas phase and in water, why aromatic amines like aniline are far weaker bases than aliphatic amines, and the effect of substituents. We then cover their reactions - alkylation, acylation, the carbylamine test, reaction with nitrous acid, the Hinsberg test, and the electrophilic substitution of aniline (bromination, nitration, sulphonation) - and finish with the most exam-rich topic of all: aromatic diazonium salts, their preparation and stability, and their reactions (Sandmeyer and Gattermann replacements, reduction, and the azo coupling reactions that make dyes). Every named reaction, basicity comparison and exam-favourite conversion is covered.