Account for the following:
(a) Aniline does not undergo Friedel Crafts alkylation
(b) Although - NH2 group is an ortho and para-directing group, nitration of aniline gives alongwith ortho & paraderivatives
meta-derivative also.

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Solution

(a) Aniline does not undergo Friedel-Crafts reaction (alkylation and acetylation) due to salt formation with aluminium chloride, the Lewis acid, which is used as a catalyst. Due to this, nitrogen of aniline acquires positive charge and hence acts as a strong deactivating group for further reaction.
(b) Direct nitration of aniline yields tarry oxidation products in addition to the nitro derivatives. Moreover, in the strongly acidic medium, aniline is protonated to form the anilinium ion which is meta directing. That is why besides the ortho and para derivatives, significant amount of meta derivative is also formed..

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- {N H}_{2}

group of aniline is ortho, para directing in electrophilic substitutions. Reason:

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Q. Amino group is ortho, para-directing for aromatic electrophilic substitution. On nitration of aniline good amount of m-nitroaniline is obtained. This is due to:

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.

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Account for the following:(a) Aniline does not undergo Friedel Crafts alkylation(b) Although - NH2 group is an ortho and para-directing group, nitration of aniline gives alongwith ortho & paraderivativesmeta-derivative also.

Account for the following:
(a) Aniline does not undergo Friedel Crafts alkylation
(b) Although - NH2 group is an ortho and para-directing group, nitration of aniline gives alongwith ortho & paraderivatives
meta-derivative also.