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TheNMR spectra of a series of 4-r-butylcydohexane-0-methyl oximes and N,N-dimethylhydrazones containing a-methyl substituents have been measured. The effects of a-methyl substitution (syn-axial, anti-axial and and-equatorial) on the carbons a, f3 and y to the substitution site are similar to those previously found in cyclohexanones. Use has been made of these substituent parameters to determine the conformational equiliiria of the mobile 2-methylcydohexnnone derivatives.The utility of 13C NMR as an important method of structural and conformational analysis of cyclohexane derivatives has been well established.',* While I3C shieldings in methylated cyclohexanones also revealed a clear dependence on the stereochemistry of the methyl substituents, the shieldings in carbonyl derivatives of these ketones have received scant attention. Acetone oxime has been studied in some and quite an extensive study of cyclic and bicyclic ketoximes, including several cyclohexanone derivatives, was made by Hawkes et aL5 Very recently, the 13C spectra of it number of tosyl hydrazones, including ten methylated cyclohexanone derivatives, have been described.6The most striking aspect of the shieldings of both the oximes and the tosyl hydrazones was the occurrence of a large difference in shieldings (7-8ppm), of the syn (2) vs anti (E) a-carbons. This difference, which also appears in amides4v7 and nitrosamines,&" is usually attributed to steric shielding of the syn carbon. As a result of our studies on the alkylation of cyclohexanone 0-methyl oximes and N,N-dimethylhydrazones" we have prepared an appreciable number of a-methylation products. On the basis of the known syn-anti shielding differential and the shielding effect of a methyl substituent on a y-carbon Series ain cyclohexanones,'* it was anticipated that the I3C shielding parameters wquld clearly indicate the stereochemistry of the alkylation products. In this paper, we wish to show that this is indeed the case, from the study of the 13C spectra of all 2-methyl and 2,6-dimethyl-4-t-butyl cyclohexanone 0-methyl ethers and N,N-dimethylhydrazones. The methyl substituent parameters obtained from the conformationally homogeneous compounds can be used to estimate the position of the conformational equilibrium in the mobile 2-methyl and 2,6-dimethylcyclohexanone derivatives. EXPERIMENTALCompounds. The methylated cyclohexanone 0-methyl oximes were prepared as described earlier by us.11 The corresponding N,N-dimethylhydrazones were prepared using essentially the same procedure as described by Corey and Enders.13 Complete experimental details will be given in a full paper.14 13C spectra. The

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