September 20, 2013
An HMBC experiment can be a key part in solving for an unknown compound. In this puzzle, ‘extra’ correlations add an extra degree of difficulty to its interpretation.
For a pure, unknown compound, the 1H -13C HMBC spectrum below shows three correlations to the carbon at 42 ppm. Can you interpret how the correlations at 4.05, 3.50 and 3.46 ppm should be assigned to the 1H signals 3.75 and 3.50 ppm?