Trying to optimize a diastereoselective reaction. It's not a double bond, it's substituted cyclohexane. Anyway, when performing a GC on the crude I get 2 nice peaks with correct mass (80:20). The separation was good but when I did the analysis again with a diffrent GC method (same sample) the cis/trans ratio changed to (65:35). Whats wrong? Epimerisation?
How do I calculate the correct ratio? Do I need to performe NMR ?