Theoretical study of electronic and steric effects in the dehydration step of norcanphor and substituted norcanphor

Abstract

The semiempirical AM1 method has been employed to calculate the dynamics of the dehydration step of norcanphor and 3-CH 3, 3-OH and 3-Cl substituted norcanphor. The reaction paths were obtained for two possible mechanisms: specific acid and general acid catalysis. The geometries have been fully optimized for the reactant, activated complexes and product for distinct mechanisms of the general acid catalysis. For norcanphor, the activation barrier obtained for specific acid catalysis was 14.12 kcal mol −1 while for the general acid catalysis this value is reduced to 4.35 kcal mol −1. Reaction-coordinate eigenvector analysis shows a breaking of the CO bond at transition states with the central carbon atom positively charged and in a configuration near sp 3 hybridization. The results indicate that, during the dehydration step, the central carbon makes a transition from an sp 3-like to an sp 2-like hybridization, which allows complete conjugation with the nitrogen atom, resulting in a carbon nitrogen double bond.