Question

How would you distinguish between the IR spectrums of Benzil, Bibenzyl, and Biphenyl? Identidy what major peaks would be present and what functional groups they would correspond to.

Answer 1

Benzil: IR spectrum of benzil shows characteristic peaks at 3010 cm^-1 due to aromatic C-H stretching and peak at 1640 cm^-1 due to C=C stretch and an intense peak at 1700 cm^-1 due to C=O stretch

Bibenzyl: IR spectrum of bibenzyl shows characteristic peaks at 3010 cm^-1 due to aromatic C-H stretching and peak at 1640 cm^-1 due to C=C stretch and CH2 stretches at 2925 and 2855 cm^-1

Biphenyl: IR spectrum of benzil shows characteristic peaks only at 3010 cm^-1 due to aromatic C-H stretching and peak at 1640 cm^-1 due to C=C stretch