A (C-D) (carbon–deuterium) bond is electronically much like a C-H bond, and it has a similar stiffness, measured by the spring constant, k. The deuterium atom has twice the mass (m) of a hydrogen atom, however.

(a) The infrared absorption frequency is approximately proportional to √k/m, when one of the bonded atoms is much heavier than the other, and m is the lighter of the two atoms (H or D in this case). Use this relationship to calculate the IR absorption frequency of a typical C-D bond. Use 3000 cm^-1 as a typical C-H absorption frequency.

(b) A chemist dissolves a sample in deuterochloroform then decides to take the IR spectrum and simply evaporates most CDCl₃. of the What functional group will appear to be present in this IR spectrum as a result of the impurity?