Important reactions of benzaldelyde

Perkin condensation

Benzoin condensation

Electrophilic substitution reaction
Aromatic aldehydes and ketones undergo electrophilic substitution at the ring in which the carbonyl group acts as a deactivating and meta-directing group.

nitration of benzaldehyde
Cannizzaro's reaction
Aldehydes which do not have an a-hydrogen atom undergo self oxidation and reduction (i.e., disproportionation) reaction on treatment with concentrated alkali. In this reaction, one molecule of the aldehyde is reduced to alcohol and another is oxidised to carboxylic acid salt.

formation of sodium formate from formaldehyde

formation of benzoic acid from formaldehyde

Aldehydes containing a-hydrogen atoms when heated with concentrated alkali give brown resinous mass.

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