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Logic Puzzle #27: Recognizing the Protonated Carbon … Solution

Given a set of data points, the elucidator aims to conjure up a variety of scenarios that are consistent with the data at hand. This puzzle aims to draw out an unlikely, but worth considering, scenario that needs to be verified.

The expanded region for the 1H-13C HSQC-DEPT spectrum presents two scenarios that are consistent with the spectral data. The obvious scenario is that the two negative correlations pertain to 1 carbon at 107.9 ppm directly correlated to 2 protons at 4.46 and 4.93 ppm existing as a single CH2 group.

The other scenario is the carbon at 107.9 ppm corresponds to 2 coinciding carbons both existing as CH2 groups. One carbon correlates to 1 proton at 4.46 ppm and the other carbon to the other proton at 4.93 ppm. The remaining geminal protons are not present in the expanded region.

The appropriate scenario can be verified by examining the full spectrum.