An organic compound (A) with molecular formula `C_(8)H_(8)O` forms an orange-red precipitate with 2,4-DNP reagent and gives yellow precipitate on heating with iodine in the presence of sodium hydroxide. It neither reduces Tollens or Fehlings reagent, nor does it decolourise bromine water or Baeyerâs reagent. On drastic oxidation with chromic acid, it gives a carboxylic acid (B) having molecular formula `C_(7)H_(6)O_(2)`. Identify the compounds (A) and (B) and explain the reactions involved.

Explanation

(i) Positive test with 2,4 DNP and negtive tests with Tollen's reagent and Fehling solution suggest that the compound [A] is a ketone. Since it responds to iodoform test `(I_(2)//NaOH)`, it must be a methyl ketone `(CH_(3)COR)`.
(ii) The molecular formula suggests a high degree pf unsaturation which is ruled out because it does not decolourise either bromine water or Baeyer's reagent. Thus, we many conclude that it is an aromatic compound and the side chain has `-COCH_(3)` group .
Thus, the compound [A] is `C_(6)H_(5)CH_(2)COCH_(3)` (I-Phenylpropanone).
The reaction involved are as follows: