Unformatted text preview: points) The IR spectrum of acetylene is available from NIST; only the portions which
include peaks are shown below. 1.2 1.2 1 1 0.8 0.8 0.6 0.6 0.4 0.4 0.2 0.2 0 900 700 500 0 3400 3200 3000 Describe, in general terms at the molecular scale, the difference between the two vibrations
whose IR signals are shown, and provide your reasoning.
The vibration at ~700
has a Q branch, so it must be a perpendicular vibration; the
mode at ~3300
has no such Q branch, and must be a parallel vibration. In fact, these
vibrations are, respectively, the C-C-H bend (which moves the H atoms perpendicularly to
the molecular axis) and the asymmetric C-H stretch (which moves the H atoms parallel to
the molecular axis).
d. (2 points) The s...
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