Write short notes on the following: (i) Carbylamine reaction (ii) Diazotisation (iii) Hofmann’s bromamide reaction (iv) Coupling reaction (v) Ammonolysis (vi) Acetylation (vii) Gabriel phthalimide synthesis.

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1.Carbylamine Reaction
This reaction is given only by primary amines
Primary amines when heated with chloroform and alcoholic caustic potash give isocynaides (carbylamines) having very unpleasant smell, which can be easily detected

C2H5NH2+ CHCl3+ 3KOH → C2H5NC + 3KCl + 3H2O

Ethylamine Ethyl isocyanide

C6H5NH2+ CHCl3+ 3KOH → C6H5NC + 3KCl + 3H2O

Aniline Phenyl isocyanide

2. Amides can directly be converted into their corresponding amines. This reaction is carried out by treating the amide with a mixture of base and bromine (KOH + Br2). This reaction is called asHofmann Bromamide reaction.

The reaction is as follows,

RCONH2+ Br2+ 4KOH → RNH2+ K2CO3+ 2KBr + 2H2O

Here we can see that the amine formed has one carbon less than that of the corresponding amide. Due to the loss of carbon atom, this reaction is also called asHofmann degradationof amides.

3.Ammonolysis of Alkyl Halides
Many organic halogen compounds are converted into amines by treatment with aqueous (or) alcoholic solution of ammonia. This reaction is generally carried out either by allowing the reactants to stand together at room temperature (or) by heating them under pressure. Displacement of halogen by NH3 yields the amine salt, from which free amine can be liberated with hydroxide ion.

CH3Cl + NH3→ CH3NH3Cl
CH3NH2+ Cl–+ H2O

The above reaction is a class of substitution reaction, which we know as nucleophilic substitution.