Question

In which region of the carbon-13 NMR spectrum would you expect to find a resonance for the carbonyl group of an aliphatic ketone? The given chemical shift ranges are approximate.
A. 50-80 ppm
B. 180-210 ppm
C. 100-150 ppm
D. 65-85 ppm
E. 9-10 ppm
F. 110-170 ppm

Answer 1

Answer:

Option B 180-210 ppm

Explanation:

C-13 NMR tells about the carbon skeleton and it is similar to proton NMR. Reference compound in C-13 NMR is tetramethylsilane (TMS) in which chemical shift of carbon is considered to be 0.0 ppm.

Chemical shift of carbon having different hybridization is different.

For example, chemical shift of sp3 hybridized carbon is in the region of 0 to 90 ppm.

Chemical shift of sp2 hybridized carbon is in the region of  110 to 220 ppm.

In aliphatic ketone, the carbolyl carbon atom is sp2 hybridized. So, C-13 chemical chemical shift range for carboly carbon is 110-220 ppm

Therefore, among the given option, option B is correct.