Question

An organic compound (A) `(C_(8)H_(8)O_(3))` was insoluble in water, dilute HCI, and `NaHCO_(3)`. It was soluble in NaOH. A solution of (A) in dilute NaOH was boiled and steam distilled and distillate was reacted with NaOH to give a yellow precipitate. The alkaline residue is acidifield to give a solid (B) `(C_(7)H_(6)O_(3))`. (B) dissolves in aqueous `NaHCO_(3)` with the evolution of gas. Identify (A) and (B).

Answer 1

i. DU in (A) `= ((2n_(C) + 2) - n_(H)/(2)=((8xx2+1)-8)/(2)= 5^(@)`
ii. Five DU and `(C:H~~1:1)` suggest benzene ring (4 DU) and 1 DU has to be accounted.
iii. It does not contain `(---COOH)` group, since it is not soulbe in `NaHCO_(3)`.
iv. It is soulbe in NaOH, which suggests an ester group `(---COOR)` and one phenoic (OH) group.
v. (A) contains three O atoms, which suggest an easer group `(---COOR)` and one phenolic (OH) group. The presence of an ester group is also indicated by the reaction of (B) with `NaHCO_(3)`.
`overset ((A)) underset (---COOR)` `overset (NaOH) underset (Boiled) rarr` Residue `overset (Steam) underset (distilled(suggests ortho compounds)) rarr` Distillate `overset (NaOH) rarr` Yellow ppt. `overset (H^(o+)) rarr` (B) `(--COOH group)` (Dissolves in `NaHCO_(3)`)
vi. Yellow precipitate with NaOH is a characteristic test for methyl salicylate.
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