Influencing of Ring Size on Germinal Interproton Coupling Constants in Exocyclic Methylene Groups

Abstract

In systems where substituent effects are constant, there is a well defined trend in the magnitude of geminal interproton coupling constants in exocyclic methylene groups with ring size. Reduction of ring size from six to five to four results in a monotonic reduction in the magnitude of J_gem. These trends apply to methylenecycloalkanes , methylenebenzocycloalkenes and α- methylenecycloalkanones . There is an indication that the trend does not continue for methylenecyclopropanes. A number of new exocyclic-methylene compounds have been designed and synthesized to provide specific experimental data.