Account for the following: (i). pKb of aniline is more than that of m

1.	Account for the following: (i). pKb of aniline is more than that of methylamine (ii). Aniline does not undergo Friedel‐Crafts reaction. (iii). Gabriel phthalimide synthesis is preferred for synthesising primary amines.
Answer» (i) Higher pk_b means, lower is the basic character i.e aniline is weaker base than methyl amine. In aniline lone pair of electron on nitrogen atom is delocalized over the benzene ring due to the resonance effect. As a result electron density on nitrogen atom decrease. In methylamine due to +I effect electron density on nitrogen atom increase. (ii) Aniline does not undergo Friedel‐Crafts reaction due to salt formation with aluminium chloride. (iii) Gabriel phthalimide reaction gives pure 1° amines.

Account for the following: (i). pKb of aniline is more than that of methylamine (ii). Aniline does not undergo Friedel‐Crafts reaction. (iii). Gabriel phthalimide synthesis is preferred for synthesising primary amines.

Answer»

(i) Higher pk_b means, lower is the basic character i.e aniline is weaker base than methyl amine. In aniline lone pair of electron on nitrogen atom is delocalized over the benzene ring due to the resonance effect. As a result electron density on nitrogen atom decrease. In methylamine due to +I effect electron density on nitrogen atom increase.

(ii) Aniline does not undergo Friedel‐Crafts reaction due to salt formation with aluminium chloride.

(iii) Gabriel phthalimide reaction gives pure 1° amines.

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