Question

Which of the following show positive test with Fehling solution why? Explain.

1) Farnesal

2) Pulegone

3) Citronellal

4) Beta-Ionone

Answer 1

Fehling's reagent is used to detect aliphatic aldehydes:

R-CHO + 2Cu²⁺ + 4OH^- = R-COOH + Cu₂O + 2H₂O

In view of this, a positive reaction will give 1) Farnesal and 3) Citronellal, because they contain an aldehyde group.