Which of the following give a red precipitate with Fehling solution on warming?

Aethanal
Bbenzaldehyde
Cphenylethanal, $C X_{6} H X_{5} CH X_{2} CHO$
Dmethanal

Answer: A, C, D

Fehling solution oxidises aliphatic aldehydes, including ethanal, methanal and phenylethanal (the CHO is attached to an sp3 carbon). Benzaldehyde, an aromatic aldehyde, does not reduce it.

Practice Aldehydes, Ketones and Carboxylic Acids More on Oxidation and reduction of carbonyls (Clemmensen, Wolff-Kishner, Tollens, Fehling)

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