The substituent effect on the carbonyl carbon [C(α)] 13C chemical shift in 3- and 4-substituted benzamides and N-chlorobenzamides has been studied in (CD3)2SO. Chlorine shields the carbonyl carbon. A cross correlation was carried out for C(α) and the carbonyl carbon in N-chlorobenzamides is less sensitive to substituents than in the benzamides. The dual substituent parameter method indicated a significant diminution in the π-polarization effect (ρ1) in N-chlorobenzamides compared to benzamides. This is in contrast to other carbonyl systems where ρ1 has been found to be essentially independent of the substituent attached to the carbonyl carbon. It is concluded that π-polarization in benzamide and its derivatives is more sensitive to the substituent attached to the carbonyl carbon than in the other classes of aromatic carbonyl compounds studied to date.
|Original language||English (US)|
|Number of pages||4|
|Journal||Journal of the Chemical Society, Perkin Transactions 2|
|State||Published - Dec 1 1993|
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