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.

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Chapter1: Chemical Foundations
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Problem 1RQ: Define and explain the differences between the following terms. a. law and theory b. theory and...
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please help with part B:

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.
b. The amide functional group is one of the more stable carbonyl containing compounds. Upon
addition of a strong reducing agent (LiAlH4), amides are reduced to amines, not alcohols.
However, certain tertiary amides do not reduce to amines, but to aldehydes. N-methyl
propamide is reduced to N-methyl propyl amine, but amides made from imidazole
(imidazolides) and aziridines are reduced to aldehydes. Come up with a resonance argument
for why N-methyl propamide will reduce to an amine while propanoyl aziridine will reduce to
propanal.
Transcribed Image Text: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. b. The amide functional group is one of the more stable carbonyl containing compounds. Upon addition of a strong reducing agent (LiAlH4), amides are reduced to amines, not alcohols. However, certain tertiary amides do not reduce to amines, but to aldehydes. N-methyl propamide is reduced to N-methyl propyl amine, but amides made from imidazole (imidazolides) and aziridines are reduced to aldehydes. Come up with a resonance argument for why N-methyl propamide will reduce to an amine while propanoyl aziridine will reduce to propanal.
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