Question

Among the following the number of reaction(s) that produce(s) benzaldehyde is :
(a)
(b)

(c)

(d)
(e)
(f)
(g)

Answer 1

(a)- It is Rosenmund reduction. It will reduce benzoyl chloride to benzaldehyde in presence of $H_2,Pd-BaS{O}_4$

(b)- DIBAL-H will reduce ester and nitrile to aldehyde. Thus, the benzonitrile is getting reduced to benzaldehyde.

(c)- It is Etard reaction. The reagent is $Cr{O}_{2}C{l}_2,C{S}_2,H_3{O}^{+}$. It will oxidise the toluene to benzaldehyde.

(d) It is a side chain chlorination followed by hydrolysis. Here, the toluene is oxidised to benzaldehyde.

(e) It is Gattermann – Koch reaction. Here, in first $CO$ and $HCl$ will react to form a formyl chloride which on reacting with $AlC{l}_3$ gives a formyl cation which will act as a electrophile for aromatic electrophilic substitutionand result in the formation of benzaldehyde.

(f) It is a Friedel-Crafts acylation reaction, since $C{H}_{3}COCl$ is taken, product will be ketone (acetophenone).

(g) Dichloromethyl benzne on reacting with water undergo hydrolysis where the two $Cl$ are replace by $OH$ group and followed by dehydration (because two OH group on single carbon is unstable) to form aldehyde group. Thus, it gives benzaldehyde.
Hence, (a), (b), (c), (d), (e) and (g) gives benzaldehyde.