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This cis-cyclohexyl derivative with two big substitutes (A and B) may has two conformational isomers, 1 and 2. How to determinie them by NMR? |
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In conformation 1, we will have 3 J"s: Jaa, Jae and Jae. Jaa is large. Two Jae may be equal, and smaller. While in conformation 2, we will have two Jea"s and one Jee. They should be similar and small. So we can identify them. Right? true, but you need to make sure that you indeed have a major conformation, not a mix of two. also it would really help to have assignment of protons - which is vicinal to A and which - to B. Hopefully there is not too much overlap in your spectrum :). - Evgeny Fadeev (Apr 05 '10 at 07:33) if you have some clear axial couplings >10 Hz then it's possible. - Evgeny Fadeev (Apr 05 '10 at 08:18) Thank you for you comments. I am no sure if it is a mixture. It is really a problem. The peak of proton geminal to A is a dd, not as expected ddd. J are 9.2 and 5.2. Unfortunately, other proton are overlapped. I would like to do a NOE experiment for further check. - Jack (Apr 06 '10 at 03:05) |
