Question

An organic compound (A) (molecular formula C₈H₁₆O₂) was hydrolysed with dilute sulphuric acid to give a carboxylic acid (B) and an alcohol (C). Oxidation of (C) with chromic acid produced (B). (C) on dehydration gives but-1-ene. Write equations for the reactions involved.

An organic compound (A) (molecular formula C₈H₁₆O₂) was hydrolysed with dilute sulphuric acid to get a carboxylic acid (B) and an alcohol (C). Oxidation of (C) with chromic acid produced (B). (C) on dehydration gives But-1-ene. Identify (A), (B) and (C) and write chemical equations for the reactions involved.

Answer 1

1. An organic compound A with molecular formula C₈H₁₆O₂ gives a carboxylic acid (B) and an alcohol (C) on hydrolysis with dilute sulphuric acid. Thus, compound A must be an ester.
2. Further, alcohol C gives acid B on oxidation with chromic acid. Thus, B and C must contain an equal number of carbon atoms. Since compound A contains a total of 8 carbon atoms, each of B and C contains 4 carbon atoms.
3. Again, on dehydration, alcohol C gives but-1-ene. Therefore, C is of straight chain, and hence, it is butan-1-ol. On oxidation, Butan-1-ol gives butanoic acid. Hence, acid B is butanoic acid.

Hence, the ester with molecular formula C₈H₁₆O₂ is butylbutanoate.

All the given reactions can be explained by the following equations:

\[\ce{\underset{\underset{(A)}{Butyl butanoate}}{CH3CH2CH2COOCH2CH2CH2CH3} + H3O+ ->\underset{\underset{(B)}{Butanoic acid}}{CH3CH2CH2COOH} + \underset{\underset{(C)}{Butanol}}{CH3CH2CH2CH2OH}}\]

\[\ce{\underset{\underset{(C)}{Butanol}}{CH3CH2CH2CH2OH}->[{[O]} Oxidation][Chromic acid (H2CrO4)]\underset{\underset{(B)}{Butanoic acid}}{CH3CH2CH2COOH}}\]

\[\ce{\underset{\underset{(C)}{Butanol}}{CH3CH2CH2CH2OH}->[Dehydration][-H2O]\underset{But-1-ene}{CH3CH2CH=CH2}}\]