An organic diabasic acid `(A)` gave the following on analysis :
`C = 57.8 %, H = 3.6 %`. Its silver salt contained `56.8 % Ag`. On heating `(A)` gives a product `(B)` which on heating with `NH_3`gives `( C) (C_8 H_5 O_2 N)`. Compound `( C)` forms potassium salt with alc. `KOH` and is converted into o-aminobenzoic acid with `NaClO`. Assign structures to `(A), (B),` and `( C)`.

Explanation

Acid `(A)` is dibasic

`1 mol` of silver salt `(I) = 2 mol of Ag`
=`2 xx 1-8 gm of Ag`
`56.8 gm of Ag = 100 gm of (I)`
`2 xx 108 of Ag =(100 xx 2 xx 108)/(56.8) = 380 gm of (I)`
Weight of dibasic acid `= (380 - 2 xx 108) + 2(for 2 H)`
=`166 gm`
Weight of `(RC) =wt. "of acid - wt, of" 2(COOH)`
=`166 - 2 xx 45 = 76 gm`
Number of `C` atom (except `COOH) = 76//12 ~~ 6`
So, six `C` atoms suggest benzene ring.
Structure of `(A)` would be :

Reaction suggest `(A)` is phthalic acid `(a)`
Reactions :
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