(I) Give the products fo the following dibasic acids on heating.
(a) .
(II) How do the following react when heated and when treated with concentrated `H_2 SO_4` :
(i) `HCOOH` and (ii) `(COOH)_2` ?

Explanation

(I) (a)
(b) Decarboxylation takes place in a similar way as `beta-keto` acid undergoes.

( c)
(d)
( e)
(f)
Cyclic ketone formed in `(e)` and `(f)` can also be prepared by dry distillation of `Ca^(2+)` or `Ba^(2+)` salts of their correcponding acids.
(g) Rings having more than six members are not stable, so `(g)` on heating forms a linear polymeric anhydride.
.
(II) (i) `HCOOH`
`H_2 O+ CO overset (Conc.) underset (H_2 SO_4) larr HCOOH overset (Delta) underset(160^@ C)rarr CO_2 + H_2`.
(ii) Oxalic acid :
.