Deuterium isotope and anomeric effects in the conformational equilibria of molecules containing CHD-O groups

摘要: The authors have recently shown that the deuterium in a CHD group cyclohexane-d/sub 1/ or 11/ prefers equatorial over axial position by 6.3 +/- 1.5 cal/mol. They now report 5,5-dimethyl-1,3-dioxane-2-d/sub (I) equilibrium isotope effect is understandable terms of n-sigma* hyperconjugation (no-bond resonance) type which also responsible, large part, for anomeric effect. latter stabilization an vs. electronegative substituent, as II. bond to substituent weakened and lengthened, whereas adjacent C-O changed opposite fashion. weakening bond, albeit reduced form, should exist when X = H