Which (------COOH) group is lost as `CO_(2)` on heating in the following?
i. ii.

Explanation

i. (----COOH) at C -1 is lost easily on heating because there is (C=O) group at `beta`-position of C -1, (COOH) group.
ii. (----COOH) at C -1 is lost because there is (-----`NO_(2)`) group at `beta`-position of C -1, (COOH) group.
iii. Both (-----COOH) group at c -1 and C -4 are lost because there is double bond at `beta`-position of both (-----COOH) groups.
iv. One (-----COOH) group is lost from C -1 position, since two (----COOH) groups are present on the same C atom. Further, (----COOH) group at C -4 is also lost on heating, because there is (----CN) group at the `beta`-position of (----COOH) group at C -4.