Question

Write the chemical equations when:
(a) Ethanal is treated with 2,4-dinitrophenylhydrazine?
(b) Propanone is treated with Zn(Hg) and conc. HCl?

Hint:

- The 2,4-DNPH test is a qualitative test for detecting aldehydes and ketones. - Clemmensen reduction is useful in removing carbonyl functional groups while retaining other sensitive groups.

Answer 1

(a) Ethanal and 2,4-Dinitrophenylhydrazine (DNPH) Reaction: Ethanal (\( CH_3CHO \)) reacts with 2,4-dinitrophenylhydrazine (\( H_2N-NH\)-Ar-\( NO_2 \)) to yield a hydrazone.

This reaction serves as a test for carbonyl groups (aldehydes and ketones).

(b) Clemmensen Reduction of Propanone with Zn(Hg) and Conc. HCl: Propanone (\( CH_3COCH_3 \)) is reduced to an alkane by its carbonyl group using zinc amalgam (Zn-Hg) and concentrated HCl.

This procedure is frequently employed for the conversion of ketones to alkanes.