Chemical Shift Range in NMR Spectroscopy

Where would the signal in the fully decoupled C NMR spectrum of trimethylamine be expected to appear?

a) 200−210 ppm

b) 190−200 ppm

c) 60−170 ppm

d) 110−130 ppm

e) 40−60 ppm

Final Answer: c) 60−170 ppm

Answer:

The signal in the fully decoupled ¹³C NMR spectrum of trimethylamine would be expected in the chemical shift range of 110−130 ppm.

Trimethylamine, which contains three methyl groups attached to a nitrogen atom, will exhibit carbon signals in the approximate chemical shift range of 110−130 ppm in its fully decoupled ¹³C NMR spectrum.

This range corresponds to the chemical environment of carbon atoms within the molecular structure of trimethylamine. The methyl groups present in trimethylamine contribute to the aliphatic (alkyl) nature of the compound, leading to the observation of carbon signals in this particular range in the C NMR spectrum.

Therefore, the correct option for the expected chemical shift range for the signal in the fully decoupled C NMR spectrum of trimethylamine is c) 60−170 ppm.