(a) Write the reactions involved in the following:

(i) Hoffmann bromamide degradation reaction

(ii) Diazotisation

(iii) Gabriel phthalimide synthesis

(b) Give reasons :

(i) $(C H_{3})_{2} N H$ is more basic than $(C H_{3})_{3} N$ in an aqueous solution.

(ii) Aromatic diazonium salts are more stable than aliphatic diazonium salts.

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Solution

(a) (i) $R C O N H_{2} + B r_{2} + 4 N a O H \to R N H_{2} + 2 N a B r + N a_{2} C O_{3} + 2 H_{2} O$

(b) (i) Because of the combined effect of inductive effect of inductive effect and solvation effect.

(ii) Due to resonance stablisation of aromatic diazonium salts.

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Similar questions

Q. Give reasons Aromatic diazonium salts are more stable than aliphatic diazonium salts.

Q. (a) Illustrate the following reaction giving suitable example(s) in each case:
(i) hoffmann bromamide degradation reaction
(ii) diazotisation
(iii) gabriel phthalimide synthesis
(b) Distinguish between the following pairs of compounds:
(i) aniline and N-methylaniline
(ii)

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

and

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

OR
(a) Write the structures of main products when benzene diazonium chloride

(C_{6} H_{5} N_{2}^{+} {C l}^{-})

reacts with the following reagents:
(i)

C u C N / K C N

(ii)

H_{2} O

(iii)

C H_{3} C H_{2} O H

(b) Arrange the following:
(i)

C_{2} H_{5} N H_{2}, C_{2} H_{5} O H, {(C H_{3})}_{3} N

-in the increasing order of their boiling point
(ii) aniline, p-nitroaniline, p-methyl aniline - in the increasing order of their basic strength

Q. What is the reason that aromatic diazonium salt is more stable than aliphatic diazonium salt?

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.

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

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(a) (i) RCONH2+Br2+4NaOH→RNH2+2NaBr+Na2CO3+2H2O (b) (i) Because of the combined effect of inductive effect of inductive effect and solvation effect. (ii) Due to resonance stablisation of aromatic diazonium salts.

(a) (i) $R C O N H_{2} + B r_{2} + 4 N a O H \to R N H_{2} + 2 N a B r + N a_{2} C O_{3} + 2 H_{2} O$

(b) (i) Because of the combined effect of inductive effect of inductive effect and solvation effect.

(ii) Due to resonance stablisation of aromatic diazonium salts.