[ijsup]

 Hi. I just did a lab where we dehydrated 2-methylcyclohexanol. We were told it would form 1-methylcyclohexene and/or 3-methylcyclohexene and we are asked to determine the major product. I figure the major product is 1-methylcyclohexene because it is the most substituted C=C. However, we are supposed to determine it using C13 NMR. We are given the "hint" to figure out how the spectra of the 1-and 30 methylcyclohexenes would differ. I don't know how to figure this out. I'm not sure what the difference between the two isomer's NMR would be. Any suggestions?

[aldoxime_amine]

alpha effect of the methyl on the sp2 hybridized carbon in the major product will cause a downfield shift while in other product, gamma effect of the methyl group will cause an upfield shift on the sp2 hybridized carbon.

Please correct me if i am wrong. I am new to spectroscopy.

[azmanam]

If you didn't decouple the ¹³C spectra, you could tell a di-sub olefin from a tri-sub.  You could also do DEPT experiments, but that may be outside the scope of your lab.

aldoxime_amine: I think that's ok, too.  sp² centers are more electronegative than sp³, so if you can identify the methyl signal in the ¹³C, you should be able to see which one is more downfield, and that will tell you which one is tri-sub.