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Account for the following with equations of the reactions involved: a) Gabriel phthalimide synthesis is preferred for preparation of primary amines. b) Explain why pKb of methanamine is 3.38 while that of aniline is 9.38.

Account for the following with equations of the reactions involved:
a) Gabriel phthalimide synthesis is preferred for preparation of primary amines.
b) Explain why pKb of methanamine is 3.38 while that of aniline is 9.38.

Grade:Upto college level

1 Answers

Gaurav
askIITians Faculty 164 Points
9 years ago
Gabrielphthalimidesynthesis results in the formation of 1° amine only. 2° or 3° amines are not formed in this synthesis. Thus, a pure 1° amine can be obtained. Therefore, Gabrielphthalimidesynthesis is preferred forsynthesizingprimary amines.


Aniline undergoes resonance and as a result, the electrons on theN-atomaredelocalizedover the benzene ring. Therefore, the electrons on theN-atomare less available to donate.

On the other hand, in case ofmethylamine(due to the +I effect of methyl group), the electron density on theN-atomis increased. As a result, aniline is less basic thanmethylamine. Thus,pKbof aniline is more than that of methylamine.




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