(i) E is monobasic acid (RCOOH) having molecular weight 60 and it is formed from D on oxidation. So E must be acetic acid and D must be acetaldehyde.
(ii) (B) on oxidation gives CH₃CHO. So (B) must be alcohol (CH₃CH₂OH).
(iii) Acetaldehyde (D) on treating with aqueous alkali (NaOH) gives aldol which on heating gives 2- butenal (E).

(iv) Compound E on catalytic hydrogenation gives butyl alcohol.

(v) Hence compound (A) must be an ester. Ester (A) on reduction with LiAIH₄ yields two alcohols (B) and (C). (A) is ethyl butyrate.

'A' can also be CH₃COOCH₂CH₂CH₂CH₃. This structure will be answering all the above reactions.

In this reaction, phenol is first converted into sodium phenoxide which is more reactive than phenol towards electrophilic substitution reaction with CO₂, Treatment of sodium phenoxide with CO₂ at 400 K, 4-7 bar pressure followed by acid hydrolysis gives salicylic acid.

\({ CH }_{ 3 }-{ CH }_{ 2 }-OH\overset { { H }_{ 2 }{ SO }_{ 4 } }{ \underset { 443k }{ \longrightarrow } } { CH }_{ 2 }={ CH }_{ 2 }+{ H }_{ 2 }O\)
Mechanism
Primary alcohols undergo dehydration by E₂ mechanism

(i) Benzylchloride to benzylalcohol
\(\underset { Benzyl \ chloride }{ { C }_{ 6 }{ H }_{ 5 }{ CH }_{ 2 }Cl } + NaOH { \longrightarrow } \underset { Benzyl \ alcohol }{ { C }_{ 6 }{ H }_{ 5 }{ CH }_{ 2 }OH } +NaCl\)
(ii) benzyalalcohol to benzoic acid
 \(\underset { Benzyl \ alcohol }{\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{CH}_{2} \mathrm{OH} }\stackrel{\mathrm{Na}_{2} \mathrm{Cr}_{2} \mathrm{O}_{7} / \mathrm{H}^{+}}{\longrightarrow}\underset { Benzaldehyde } {\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{CHO}}\stackrel{\mathrm{Na}_{2} \mathrm{CrO}_{7} / \mathrm{H}^{+}}{\longrightarrow} \underset { Benzoic \ acid } {\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{COOH}}\)