Question

Question: Treatment of benzaldehyde (${\mathbf{C}}_{\mathbf{6}}{\mathbf{H}}_{\mathbf{5}}\mathbf{CHO}$) with Zn(Hg) in aqueous HCl forms a compound Z that has a molecular ion at 92 in its mass spectrum. Z shows absorptions at 3150–2950, 1605, and 1496 cm^-1 in its IR spectrum. Give a possible structure for Z.

Short answer

Answer

Step-by-step solution

Clemmensen reduction

In Clemmensen reduction, a double-bonded oxygen is reduced to an alkyl group in the presence of Zn(Hg) and aqueous HCl. Only the double-bond oxygen is reduced in Clemmensen reduction. Benzaldehyde reacts with Zn(Hg) in aqueous HCl to form toluene.

Structure determination

m/z = 92; molecular formula ${\mathrm{C}}_7{\mathrm{H}}_8$IR absorptions at 3150–2950 ${\mathrm{cm}}^{-1}$ = C sp³-H and C sp²-H bonds 1605 ${\mathrm{cm}}^{-1}$and 1496 ${\mathrm{cm}}^{-1}$due to the phenyl group.

${\mathrm{C}}_7{\mathrm{H}}_8$structure of toluene