For example, take methyl phenyl acetate, we can see the chemical shifts is at 7.4 ppm, singlet, 5H; 3.6 ppm, singlet, 3H and 3.5 ppm, singlet 2H. Let us say we didn't know the identity of the compound and just its molecular formular C9H10O2.

I knew that of the 3.6 ppm, singlet, 3H signal I would get CH3-O, but I had trouble thinking about the 3.5 ppm, singlet, 2H. I later found out that the methylene group -CH2 was sandwiched between the carbonyl and the benzene ring, which made me think if this was a pattern for all methylenes sandwiched between a carbonyl and a benzene ring.

  • $\begingroup$ TL;DR: probably, but not guaranteed. Basically, you are asking if NMR spectra can be predicted and if the two neighbor groups are enough for predicting NMR of the metilene group. The answer for the first is "kinda, unless something weird and/or special happens, like non-obvious contact with a group capable to influence chem. shift through space (benzene ring and other non-saturated systmes, for example)". The answer for the second would probably be "yes, with a list of exceptions (strong pi-donors/pi-acceptors in benzene ring for exaple". $\endgroup$ – permeakra Jan 5 '18 at 0:03
  • $\begingroup$ Sandwich has specifically chemical meaning so your post can be a bit misleading. $\endgroup$ – Mithoron Jan 5 '18 at 0:17

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