Question

An organic compound 'A' (molecular formula C6H8O) gives 2,4-DNP test. It does not give Tollen’s test, but gives a yellow precipitate 'B' with NaOH and I2. On drastic oxidation, it gives a carboxylic acid 'C' with formula C7H6O2. Identify 'A', 'B', 'C' and write the reactions involved.

Hint:

Iodoform test is positive for aldehydes and methyl ketones. Benzaldehyde reacts with iodine and NaOH to give a yellow precipitate of iodoform.

Answer 1

- 'A' is benzaldehyde (C6H5CHO). - 'B' is the yellow precipitate formed by the reaction of benzaldehyde with NaOH and iodine, forming iodoform (CHI3). - 'C' is benzoic acid (C6H5COOH), formed by the oxidation of benzaldehyde.
Reactions:
1. 2,4-DNP test:
\chemfig{C_6H_5CHO} + DNP $\rightarrow$ \text{Yellow precipitate (2,4-DNP derivative)}
2. Iodoform test:
\chemfig{C_6H_5CHO} + NaOH + I_2 $\rightarrow$ \text{Yellow precipitate of iodoform (CHI3)}
3. Oxidation:
\chemfig{C_6H_5CHO} + [O] $\rightarrow$ \chemfig{C_6H_5COOH}