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- O=NR2). (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- O=NR2). (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.

Chemistry

10th Edition

ISBN:9781305957404

Author:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste

Publisher:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste

Chapter1: Chemical Foundations

Section: Chapter Questions

Problem 1RQ: Define and explain the differences between the following terms. a. law and theory b. theory and...

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