Textbook Question
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 the square root of 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 (CDCl3)
and then decides to take the IR spectrum and simply
evaporates most of the CDCl3. What functional group
will appear to be present in this IR spectrum as a result
of the CDCl3 impurity?
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