AN ISOTOPIC AND EPR PROBE INTO HYPERCONJUGATIVE AND INDUCTION EFFECTSIN P-XYLENE

EPR studies show that the anion radicals of alpha,alpha,alpha-d3-p-xyl ene and alpha,alpha'-d6-p-xylene (CD3-C6H4-CD3.-) exhibit hyperfine co upling constants for the ring protons that are 12 and 23 mG larger tha n those of the p-xylene anion radical itself. This has been attributed to a further lifting of the degeneracy of the antibonding molecular o rbitals due to the replacement of the protons with deuteriums to an ex tent of 29 J/mol per deuterium. These results seem to support the conc lusion that both inductive and hyperconjugative effects are responsibl e for the lifting of this degeneracy due to the methyl groups.