Q.Benzaldehyde does NOT show positive test with
a. Schiff reagent
b. Tollens' ragent
c. Sodium bisulphite solution
d. Fehling solution

Step 1. Recall which tests respond to -CHO in general (section 12.8.1). Schiff's test, Tollens'/silver-mirror test, and sodium bisulfite addition all respond simply to the presence of an aldehydic -CHO group as such, regardless of whether the aldehyde is aliphatic or aromatic -- benzaldehyde gives a positive Schiff test, deposits a silver mirror with Tollens' reagent, and forms a bisulfite adduct exactly as any other aldehyde does. …

Distinguishing which of the four listed aldehyde tests genuinely require aliphatic/enolisable character (Fehling) from those that respond to any -CHO grou …

• Assuming benzaldehyde fails ALL the classic aldehyde tests just because it is aromatic, when in fact Schiff's, Tollens' and sodium bisulfite all still work on it. …