H-NMR Questions/confusion

[bakeit1]

Ok, im having a lot of trouble with a lab I did. The lab was the hydroboration of 1-phenylcyclohexane. There are three outcomes of this reaction: 1-phenylcyclohexanol (Markov. addition), cis-2-phenylcyclohexanol (anti-markov. anti addition), or trans-2-phenylcyclohexanol (anti-markov. syn addition).

 

Now, it's clear that the third outcome would be the major product. However, I was given an H-NMR of this compound and the questions asks how do I know, based on the H-NMR, that the third outcome is correct? What peaks or absense of such peaks can be used to determine this?

 

The peaks on my NMR sheet are: a singlet on 0 PPM, a sextet between 3 and 4, and another singlet between 7 and 8. My teacher said the meat of this mystery lies with the sextet between 3-4. I am struggling and havn't a clue what to look for, please help. Thanks.

[hermanntrude]

consult nmr correlation tables and try to figure out what peaks should be where for each proton and what the splitting pattern ought to be. Then decide which pattern your nmr looks most like.

 

There is some software that can predict nmr spectra but you need to know how to do it without the software too

[Tartaglia]

I assume you mean 1 phenylcyclohexene

 

The coupling constant will be important here between the H on the same carbon as the phenyl and the H on the same carbon as the hydroxyl. The phenyl will sit equatorial with the 6 membered ring in the chair. This will place both the afore mentioned Hydrogens in axial positions with a large coupling constant > 8Hz for syn addition. For the antiaddition which obviously won't occur the hydrogens will be axial and equatorial and the coupling will be less 3-5Hz roughly.