question_answer

Among the following compounds those cannot be prepared by Gabriel method from their corresponding halides of tosylates are I. 1 - butylamine;            II. Neopentylamine III. Diethylamine             IV. p - toluidine V. m - nitro aniline          VI. Vinylamine   VII. p - nitro aniline         VIII. o -nitro aniline IX. Allyl amine Choose the correct option.

A)  I, II, VI, VII. VIII          

B)  I, II, III, IV, V, VI           

C)  III, IV, V, VI, IX           

D)  All of these

Correct Answer: B

Solution :

Halides or tosylates which are unreactive in \[{{S}_{N}}2\] cannot be used. I to VI cannot be prepared but VII to IX can be prepared. I. It cannot be prepared since \[M{{e}_{3}}C-X\] is a \[3{}^\circ \] halide. II. It cannot be prepared since \[\,M{{e}_{3}}C-C{{H}_{2}}-X\] is neopentyl halide and does not undergo \[{{S}_{N}}2\] reaction due to steric hindrance. III. It cannot be prepared since \[2{}^\circ \] amine gives poor yield due to elimination. IV. It cannot be prepared since arylhatide  is not activated by electron donating group (Me group). \[Ar{{S}_{N}}\] reaction takes place only when the benzene ring is activated by electron withdrawing group present at o- and p-positions. V. It cannot be prepared, since electron withdrawing group (\[-N{{O}_{2}}\] group) is present m-position.  \[Ar{{S}_{N}}\] reaction does not take place. VI. It cannot be prepared, since vinyl halides \[(C{{H}_{2}} = CM -X)\] are unreactive in \[{{S}_{N}}2\] reaction. VII. It can be prepared, since ?benzene ring  is activated by electron withdrawing group \[\left( -N{{O}_{2}} \right)\] at p-position and hence \[Ar{{S}_{N}}\] reaction takes place. VIII. It can be prepared since benzene ring, is activated by electron withdrawing group\[\left( -N{{O}_{2}} \right)\] at o-position and hence \[Ar{{S}_{N}}\] reaction takes place. IX. It can be prepared since allyl halides \[\left( C{{H}_{2}} = CHC{{H}_{2}}X \right)\] can undergo \[{{S}_{N}}2\] reaction.