Account for the following:
(i) Primary amines $(R - N H_{2})$ have higher boiling point than tertiary amines $(R_{3} N)$ .
(ii) Aniline does not undergo Friedel-Crafts reaction.
(iii) ${(C H_{3})}_{2} N H$ is more basic than ${(C H_{3})}_{3} N$ in an aqueous solution.

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Solution

(i) Due to intermolecular hydrogen bonding in primary amines (presence of more number of H-atoms ).

(ii) Because aniline is basic in nature and reacts with $A l C l_{3}$ to form salt. The positive charge on the N-atom, electrophile substitution in the benzene ring is deactivated. (refer to given image)

(iii) Due to steric hindrance and solvation factor in case of ( $C H_{3})_{3} N$ , it is less basic than ( $C H_{3})_{2} N H$ in aqueous solution.

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Q. Give reasons for the following:
(i) Aniline does not undergo Friedal- Crafts reaction.
(ii)

(C H_{3})_{2} N H

is more basic than

(C H_{3})_{3} N

in an aqueous solution.
(iii) Primary amines have higher boiling point than tertiary amines.

Q. Amines are classified as primary, secondary and tertiary amine.
(a) Represent the structure of secondary and tertiary amine.
(b) How will you convert nitrobenzene to aniline?
(c) Aniline does not undergo Friedel-Crafts reaction. Why?

Account for the following

(i) $p K_{b}$ of aniline is more than that of methyl amine.

(ii) Ethylamine is soluble in water whereas aniline is not

(iii) Methyl amine in water reacts with ferric chloride to precipitate hydrated ferric oxide

(iv) Although amino group is o- and p- directing in aromatic electrophilic substitution, aniline on nitration gives a substantial amount of m-nitroaniline

(v) Aniline does not undergo Friedel Crafts reaction

(vi) Diazonium salts of aromatic amines are more stable than those of aliphatic amines

(vii) Gabriel phthalimide synthesis is preferred for synthesising primary amines

Account for the following:

(i) pK_bof aniline is more than that of methylamine.

(ii) Ethylamine is soluble in water whereas aniline is not.

(iii) Methylamine in water reacts with ferric chloride to precipitate hydrated ferric oxide.

(iv) Although amino group is o, p− directing in aromatic electrophilic substitution reactions, aniline on nitration gives a substantial amount of m-nitroaniline.

(v) Aniline does not undergo Friedel-Crafts reaction.

(vi) Diazonium salts of aromatic amines are more stable than those of aliphatic amines.

(vii) Gabriel phthalimide synthesis is preferred for synthesising primary amines.

Give plausible explanation for each of the following:

(i) Why are amines less acidic than alcohols of comparable molecular masses?

(ii) Why do primary amines have higher boiling point than tertiary amines?

(iii) Why are aliphatic amines stronger bases than aromatic amines?

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Account for the following:(i) Primary amines (R−NH2) have higher boiling point than tertiary amines (R3N).(ii) Aniline does not undergo Friedel-Crafts reaction.(iii) (CH3)2NH is more basic than (CH3)3N in an aqueous solution.

Account for the following:
(i) Primary amines $(R - N H_{2})$ have higher boiling point than tertiary amines $(R_{3} N)$ .
(ii) Aniline does not undergo Friedel-Crafts reaction.
(iii) ${(C H_{3})}_{2} N H$ is more basic than ${(C H_{3})}_{3} N$ in an aqueous solution.