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Logic Puzzle #23: That’s a Fragment? … Solution

With each piece understood, a fragment(s) will emerge.

From the 1H-13C HSQC spectrum, there are 3 CHn groups where n represents 1, 2 or 3 protons. The proton integrals indicate 2 CHs and 1 CH3 group. The CH3 group is observed as a singlet with 1H and 13C chemical shifts at 3.35 and 56.93 ppm; this suggests an O-CH3 group. The high 1H and 13 chemical shifts for the 2 CH groups, > 70 ppm, indicates another O atom, possibly an OH or ester group. Each CH group cannot be bonded to more than 1 O atom, thus ruling out the ester possibility. Note C atoms bonded with 2 O atoms typically exhibit chemical shifts greater than 90 ppm.

In all, the three-carbon fragment is most likely a methoxy ethyl fragment.