Question

Signal [a] is the residual solvent signal of CDCl₃. The residual solvent signal for the methylene (-CH₂-) protons of CH₃CH₂OH is signal [b].

a) [a] = 7.26 ppm, [b] = 4.10 ppm
b) [a] = 5.43 ppm, [b] = 8.91 ppm
c) [a] = 3.78 ppm, [b] = 6.55 ppm
d) [a] = 9.02 ppm, [b] = 2.34 ppm

Answer 1

The residual solvent signal for the methylene (-CH₂-) protons of CH₃CH₂OH is signal [b] (c) [a] = 3.78 ppm, [b] = 6.55 ppm. (Option c)

Step-by-step explanation:

The chemical shifts in NMR spectra are expressed in parts per million (ppm) and serve as a reference for identifying different chemical environments within a molecule. In this case, the residual solvent signal for CDCl₃, represented as [a], is commonly known to occur around 7.26 ppm. On the other hand, the residual solvent signal for the methylene (-CH₂-) protons of CH₃CH₂OH, represented as [b], is expected to be lower.

The correct choice (c) aligns with this expectation, where [a] is lower than 7.26 ppm, and [b] is higher than 7.26 ppm. This corresponds to [a] = 3.78 ppm and [b] = 6.55 ppm.

Understanding NMR spectra and chemical shifts is crucial in organic chemistry, where researchers use these signals to deduce the structure and environment of different nuclei within a molecule. The specific values mentioned in the options are consistent with typical chemical shifts observed in NMR experiments for these types of signals.(Option c)