DEUTERIUM-ISOTOPE EFFECTS ON C-13 NMR CHEMICAL-SHIFTS OF AMIDES

Exchange of amide protons with deuterium results in changes of C-13 ch emical shifts for carbon atoms near the site of substitution (CH-N and N-C=O). There is a measurable decrease in the isotopic shifts of CH-N for cycloalkylacetamides as ring size increases from 3 to 8 and for l actams as ring size increases from 5 to 9. The isotopic shifts of N-C= O for lactams also decrease as ring size increases from 5 to 9 but rem ains fairly constant for cycloalkylacetamides (three- to eight-membere d rings). (C) 1997 Academic Press.