Question

Which of the following aldehydes can produce $1^o$ alcohols when treated with Grignard reagent?

• A. Methanal
• B. Ethanal
• C. Propanal
• D. Butanal

Answer 1

The correct option is A Methanal

Grignard reagent is a strong nucleophile. It undergoes nucleophilic addition reaction when it reacts with aldehyde, ester and ketone.
Grignard reagent reacts with formaldehyde to form $1^{\circ }$ alcohol.
Grignard reagent reacts with aldehyde except formaldehyde to form $2^{\circ }$ alcohol.

Methanal on treatment with Grignard reagent forms an adduct which has only one alkyl group attached to the C atom along with two hydrogens and one O-MgX (X=halogen) group. This on hydrolysis will form a primary alcohol where the OH group will replace the O-MgX group.
$RMgX+HCHO\stackrel{H_3{O}^{+}}{\to }RC{H}_{2}OH+Mg\left(OH\right)X$
Hence correct option is a.