The Question : Account for the following: a. Aniline cannot be prepared by the ammonolysis of chlorobenzene under normal conditions. b. N-ethylethanamine boils at 329.3K and butanamine boils at 350.8K, although both are isomeric in nature. c. Acylation of aniline is carried out in the presence of pyridine.
Solution for the question :
(a) In case of chlorobenzene, the C—Cl bond is quite difficult to break as it acquires a partial double bond character due to conjugation. So Under normal conditions, ammonolysis of chlorobenzene does not yield aniline.
(b) Primary and secondary amines are engaged in intermolecular association due to hydrogen bonding between the nitrogen of one and hydrogen of another molecule. Due to the presence of three hydrogen atoms, the intermolecular association is more in primary amines than in secondary amines as there are two hydrogen atoms available for hydrogen bond formation in it.
(c) During the acylation of aniline, stronger base pyridine is added. This done in order to remove the HCl so formed during the reaction and to shift the equilibrium to the right-hand side.
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