Question

This set contains the spectra of benzil, biphenyl, and bibenzyl, three compounds used in the melting point experiment. Using your knowledge of IR spectroscopy and the structures of these three compounds, determine which spectrum belongs to which compound and give a brief (one sentence) explanation of your choice.

Answer 1

Answer:

Spectrum 1- Biphenyl

Spectrum 2 - Benzil

Spectrum 3 - Bibenzyl

Explanation:

For Benzil:

The Spectrum -  2  shows this compound.The C=O and C-H bond stretching observed at following values.

$C=O \,at\,1657cm^{-1}$

$C=H \,at\,3063cm^{-1}$

For Biphenyl:

Spectrum -  1  shows this compound.

There are stretching vibrations from $3061, 3032\,and \,1597 -1428cm^{1}$ due to C-H stretching and C-C stretching respectively of aromatic ring only.

For Bibenzyl:

Spectrum - 3  shows this compound

There are stretching vibrations at $3057,3026 and 1598 - 1449cm^{-1}$ due to C-H stretching and C-C stretching of aromatic ring.

Along with this, stretching vibrations at $2943 - 2917 cm^{-1}$due to C-H of alkyl.