a. The carbonyl group of an amide is less reactive towards nucleophilic substitution reactions because of the so-called amide resonance interaction of nitrogen lone pair (RC=ONR’2 → RC- ON R2). (Relative reactivities of carbonyl compounds, increasing reactivity: nitriles < amides < esters, acids << ketones < aldehydes < acid chlorides.) However, the amides formed from imidazole (N- acylimidazoles) are highly reactive, and can be used to deliver acyl groups in much the same way as "active" esters, acid anhydrides and acid chlorides. An advantage to using N-acylimidazoles is that the imidazole that is released serves a base so additional base does not need to be added. Imidazole amides have been used in peptide and nucleoside chemistry to attach -amino acid residues to alcohols and amines. Using N-propanoylimidazole and N,N-dimethylpropanamide as examples explain why the imidazole amide is a good acylating agent.

a. The carbonyl group of an amide is less reactive towards nucleophilic substitution reactions because of the so-called amide resonance interaction of nitrogen lone pair (RC=ONR’2 → RC- ON R2). (Relative reactivities of carbonyl compounds, increasing reactivity: nitriles < amides < esters, acids << ketones < aldehydes < acid chlorides.) However, the amides formed from imidazole (N- acylimidazoles) are highly reactive, and can be used to deliver acyl groups in much the same way as "active" esters, acid anhydrides and acid chlorides. An advantage to using N-acylimidazoles is that the imidazole that is released serves a base so additional base does not need to be added. Imidazole amides have been used in peptide and nucleoside chemistry to attach -amino acid residues to alcohols and amines. Using N-propanoylimidazole and N,N-dimethylpropanamide as examples explain why the imidazole amide is a good acylating agent.

Organic Chemistry: A Guided Inquiry

2nd Edition

ISBN:9780618974122

Author:Andrei Straumanis

Publisher:Andrei Straumanis

Chapter8: Addition Via Carbocation

Section: Chapter Questions

Problem 32CTQ: The hydration above is one of a family of reactions called electrophilic addition reactions.Explain...

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