Proton n.m.r. spin-tickling studies of 13C-labeled compounds. The correlation of J(C,H) and J(H,H)

✍ Scribed by James L. Marshall; Ruth Seiwell

• Publisher: John Wiley and Sons
• Year: 1976
• Tongue: English
• Weight: 684 KB
• Volume: 8
• Category: Article
• ISSN: 0749-1581
• DOI: 10.1002/mrc.1270080806

✦ Synopsis

Abstract

A tabulation has been compiled for twenty ^13^CH coupling constants of various carboxylic acids and includes ^2^J(C,H), ^3^J(C,H) and ^4^J(C,H) values of olefins (both cis and trans); ^3^J(C,H), ^4^J(C,H) and ^5^J(C,H) values of aromatics; ^3^J(C,H) and ^4^J(C,H) values of acetylenes; and ^2^J(C,H) and ^3^J(C,H) values of rigid aliphatics. This tabulation has been completed in the present study by the spin‐tickling proton n.m.r. study of ^13^C‐carboxyl‐endo‐1,2,3,4,7,7‐hexachloronorbornene‐5‐carboxylic acid, which has established that the ^2^J(C,H) value is negative and the ^3^J(C,H) values (both cis and trans) are positive in this system. A plot of these twenty J(C,H) values vs the corresponding J(H,H) values of geometrically equivalent model systems (where there is a proton in place of a carboxyl group) gives a correlation coefficient of 0·975 (with a slope of 0·62), indicating that carbon–proton and proton–proton couplings operate by similar mechanisms throughout this broad series of structural types.