1. Amines

Chapter 13: Organic Compounds contaning Nitrogen


Amines are derivatives of ammonia in which one or more hydrogen atoms are replaced by alkyl group(s).

Amines are classified as primary, secondary and tertiary depending on the number of alkyl groups attached to nitrogen atom.

General methods of preparation

(1) Ammonolysis of alkyl halides and alcohols :

(a) From Ammonolysis of alkyl halides (Hofmann's ammonolysis) : When an aqueous solution of ammonia is heated with alkyl halide all the three types of amines and quaternary ammonium salt are formed.

                                                                                                                                                                                      (Quaternary ammonium salt)

If ammonia is taken in excess, 1° amine is the main product.

(b) Ammonolysis of alcohols : When ROH and NH3 are passed over At2O3 or ThO2 at 350°  

Call the three types of amines are formed.                   

  • Quaternary ammonium hydroxide is not formed.
  • If excess of ammonia is used, then main product will be primary amine.

(2) By reduction :


(b) With RCN : RCN + 4[H]   RCH2NH2

This reaction (b) is called mendius reaction.

The reduction of alkyl isocynides gives secondary amines.


(c) With Oximes : R­–CH=N–OH + 4[H]RCH2–NH2 + H2O

(d) With RNO2 : RNO2 + 6[H]  RNH2 + 2H2O

Sn/HCl is used in laboratory preparation

(3)     By hydrolysis of :

(a) R–NC : Alkyl isocyanide undergoes hydrolysis with mineral acid and forms alkyl amine.


(b) RNCO : Alkyl isocyarlate undergoes hydrolysis on heating with KOH and form alkyl amine.

(4) By Hofmann's bromamide reaction (Hofmann's Hypobromite reaction) : This is a general method for the conversion of alkanamides into primary amines having one less carbon.

(5)  From Grignard reagent : Alkyl magnesium iodide reacts with chloramine to yield alkyl amine.

(6) Gabriel phthalimide synthesis : Phthalimide is first treated with KOH to obtain potassium phthalimide which is then treated with alkyl iodide. Then alkyl phthalimide  on hydrolysis yields alkylamine. This method is used in the formation of pure aliphatic primary amines.

Phthalic acid

  • Aniline is not formed by this reaction.

(7) Curtius reaction :

(8) Schmidt reaction : In presence of conc. H2SO4 alkanoic acid reacts with hydrazoic acid (N3H) followed by hydrolysis to yield alkylamine.

2. Aniline


General Methods of Preparation

(1) Lab method :


(2) Industrial method :


(3) From phenol :


(4) From benzamide (Hoffmann's bromamide reaction) :

C6H5CONH2 + Br2 + 4KOH ¾® C6H5NH2 + K2CO3 + 2KBr + 2H2O

(5) Form benzoic acid (Schmidt reaction) :

(Hydrazoic acid)

(6) From Grignard reagent :          

(7) From phenyl isocyanide :

Physical properties

(i) Fresh, aniline is a colorless oily liquid. On standing the colour becomes dark brown due to action of air and light.

(ii) It's B.P. is 183ºC.

(iii) It is heavier than water.

(iv) It has characteristic unpleasent odour. It is toxic in nature.

Reactions due to –NH2 group

(1) Basis nature : Aniline is weak base but it forms salt with strong acids. It accepts a proton.

(2) Alkylation : Aniline reacts with alkyl halides forming secondary, tertiary and quaternary ammonium salts depending on the concentration of alkyl halides.

(3) Acylation : Aniline reacts with acid chlorides or anhydrides to form corresponding amides called anilides. [The reaction of C6H5NH2 with benzoyl chloride is example of "Schotten Baumann reaction"]             

(4) Carbylamine reaction :

 C6H5NH2 + CHCl3 + 3KOH ¾®C6H5NC + 3KCl + 3H2O

                                                          Phenyl isocyanide (Foul smell compound)

Note :

(1) Intermediate species is dichloro carbene [: CCl2].

(2) This is test of aniline and other primary amine, known as Isocynide test.

(5) Hoffmann's mustard oil reaction : When aniline is heated with alc. CS2 and excess of HgCl2 Phenyl isothiocyanate having a characteristic smell of mustard oil is formed.

This is a test of aniline and other primary amines.       

(6) Reaction with aldehydes : Aniline condenses with aldehydes to form schiff's base.

(7) Reaction with hinsberg's reagent :

(8) Diazotisation : Diazotisation is a reaction in which ice cooled solution of aniline in an inorganic acid reacts with sodium solution leading to the formation of diazonium salt.

Benzene diazonium chloride is a useful synthetic reagent. It is used in the preparation of many organic compounds.

(1) Halogenation : In Polar and nonpolar medium Chlorine and bromine react with aniline and form trichloro and tribromo aniline respectively.

Note : However, monobromo or chloro derivative of aniline can be prepared if –NH2 group is first protected by acetyl group. Here the reactivity decreases due less +M effect on benzene ring.

(2) Nitration :

(3) Sulphonation : Aniline reacts with fuming H2SO4 to give sulphanilic acid. (p-Amino-benzene sulphonic acid)

  • This process is called baking.
  • Sulphanilic acid is an important intermediate in the manufacturing of dyes and durgs.
  • The compounds in which both proton donating & proton accepting groups present are called ampholite (dipolare ion)

(4) Catalytic hydrogenation: Aniline undergoes hydrogenation in presence of Ni at high temp. to form cyclohexanamine.

Tests of aniline

(i) Carbylamine test : Aniline gives carbylamine test or isocyanide test.

                    C6H5NH2 + CHCl3 + KOH ¾® C6H5NC    (Bad smelling)

(ii) Dye test : Aniline is first diazotised. On adding alkaline solution. Of b-naphthol to the diaztised product a red-orange dye is formed.

(iii) On heating with bromine water, a white ppt. is formed.

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