1H NMR of Carvone

[jacknife360]

I cannot work out this 1H NMR spectra of d(+) carvone.

 

The peaks have (from left to right) the relative intensities 1, 2, 5 and 6. This adds up to the 14 protons that carvone has, but apart from that I can't work out which peaks correspond to which proton environments. Thanks for any help.

[Skye]

Since this is homework I don't think folks should tell you the answer. First, unless you have them memorised you need a chart of the shifts that are associated with each bond.

 

http://www.cem.msu.edu/~reusch/OrgPage/nmr.htm

 

Next, look at your molecule and work out where the (four) unique proton environments are. I'd probably draw it with all the H's on so I could see them more easily. Then you can assign the peaks. To start you off, the peaks at about 1 will usually be saturated alkanes protons. The peaks at 7 and 5 are probably fairly easy to figure out because there aren't too many options. Once you've narrowed it down it's easier to figure out what the remaining peaks are.

[jacknife360]

Problem is, I count 7 different proton environments. 2 different methyls, a CH2 on an alkene and those on the ring (4 different environments).

 

The peak with an itensity of 1 is not split, so must be near no inequivalent proton environment? Where is that proton?

 

The intensity of 6 also puzzles me, because I can't find any proton environment with 6 protons in.

 

It's prep for labs, they only start in a week... plenty of time!