An organic compound `(A) (C_5 H_8 O_3)` on heating with soda lime gives `(B)` which reacts with `HCN` to give `( C)`. The compound `( C)` reacts with thionyl chloride to produce `(D)` which on reaction with `KCN` gives a compound `( E)`. Alkaline hydrolysis of `( E)` gives a salt `(F)` which on heating with soda lime produces `n-butane`. Careful oxidation of `(A)` with dichromate give acetic acid and malonic acid. Give the structures to `(A)` to `(F)` with proper reasoning.

Explanation

On oxidation only two -COOH groups can be introduced i.e, one to each carbon undergoing C-C fission, but in the resulting products we have three -COOH groups. Hence, one -COOH group is already there in compound A, the remaining portion `C_(4)H_(7)O-` resembles with Keto substituted alkyl group `C_(3)H_(7)-underset(O)underset(||)(C)-` this indicates that the given organic compound A is keto substituted acid. To assign position to Keto group in carbon chain, we know that keto acids on careful oxidation undergo C-C bond fission at a place where `-overset(O)overset(||)(C)-` is situated, further keto gropup is also converted into -COOH and remains with acids is formed from `CH_(3)-overset(O)overset(||)(C)-` Arragements `C_(3)H_(7)CO-` has `CH_(3)-overset(O)overset(||)(C)-CH_(2)-CH_(2)-` structure and compound A is `CH_(3)-overset(O)overset(||)(C)-CH_(2)-CH_(2)-CO OH` A, with soda-lime undergoes decarboxylation to give `CH_(3)-CO-CH_(2)-CH_(3)(B)` B. being ketone will give addition product with HCN to form