Account for the following : (i) Primary amines (R-NH_(2)) have higher boiling points than tertiary amines (R_(3)N). (ii) Aniline does not undergo Friedel-Crafts reaction. (iii) (CH_(3))_(2)NH is more basic than (CH_(3))_(3)N in an aqueous solution.

Account for the following : (i) Primary amines (R-NH_(2)) have higher

1.	Account for the following : (i) Primary amines (R-NH_(2)) have higher boiling points than tertiary amines (R_(3)N). (ii) Aniline does not undergo Friedel-Crafts reaction. (iii) (CH_(3))_(2)NH is more basic than (CH_(3))_(3)N in an aqueous solution.
Answer» Solution :(i) Primary amines are engaged in INTERMOLECULAR association due to hydrogen bonding between nitrogen of ONE and hydrogen of another molecule. This raises the boiling point of primary amine. There is no hydrogen in tertiary amines. Hence, no hydrogen bonding. THUS, primary amines have higher boiling point than tertiary amines. (ii) Aniline does not undergo Friedel-Crafts reaction due to salt formation with aluminium chloride which is the catalyst in the reaction. Due to this, nitrogen of aniline acquires positive charge and hence acts as a strong deactivating group for further reaction. According to inductive effect `(CH_(3))_(3)N` should be more basic than `(CH_(3))_(2)NH`. According to hydrogen bonding of substitued ammonium ion, `(CH_(3))_(2)NH` should be more basic than `(CH_(3))_(2)N`. Then there is the steric effect of the methyl group. The net RESULT of all these FACTORS is that `(CH_(3))_(2)NH` is more basic than `(CH_(3))_(3)N`.