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Question: An organic compound [X] (Molecular formula C6H12O2) reacts with dil. H2SO4 to form an alcohol [B] an...

An organic compound [X] (Molecular formula C6H12O2) reacts with dil. H2SO4 to form an alcohol [B] and a carboxylic acid [C]. Reaction of compound [B] with Jones reagent yielded compound [C]. When compound [C] was heated with P2O5 an Anhydride was formed. Compound [X] is ---------.

A

CH3-COO-(CH2)3-CH3

B

CH3-COO-C-(CH3)3

C

CH3-COO-CH2-CH-(CH3)2

D

C2H5-COO-(CH2)2-CH3

Answer

D

Explanation

Solution

The problem describes a series of reactions starting from an organic compound [X] with molecular formula C6H12O2.

  1. Hydrolysis of [X]: Compound [X] (C6H12O2) reacts with dilute H2SO4 to form an alcohol [B] and a carboxylic acid [C]. This indicates that [X] is an ester, as esters hydrolyze under acidic conditions to yield a carboxylic acid and an alcohol. Let [X] be R-COO-R'. R-COO-R' + H2O →dil. H2SO4\xrightarrow{\text{dil. H2SO4}} R-COOH ([C], carboxylic acid) + R'-OH ([B], alcohol)

  2. Oxidation of [B]: Alcohol [B] reacts with Jones reagent (a strong oxidizing agent) to yield carboxylic acid [C]. R'-OH →Jones reagent\xrightarrow{\text{Jones reagent}} R-COOH For an alcohol to be oxidized to a carboxylic acid, it must be a primary alcohol. If [B] is R'-OH, and its oxidation product is R-COOH, then the carbon skeleton of [B] must correspond to [C] such that the -CH2OH group in [B] becomes the -COOH group in [C]. This means R' must be R-CH2-. So, [B] is R-CH2-OH. And [C] is R-COOH. Therefore, the ester [X] is R-COO-CH2-R.

  3. Dehydration of [C]: Carboxylic acid [C] when heated with P2O5 forms an anhydride. P2O5 is a dehydrating agent, and carboxylic acids form anhydrides upon dehydration. 2 R-COOH →P2O5, Δ\xrightarrow{\text{P2O5, } \Delta} (R-CO)2O + H2O This confirms [C] is a carboxylic acid.

Determining the structure of R: The molecular formula of [X] is C6H12O2. We deduced that [X] has the structure R-COO-CH2-R. Let 'n' be the number of carbon atoms in the alkyl group R. The total number of carbon atoms in R-COO-CH2-R is: n (from first R) + 1 (from -COO-) + 1 (from -CH2-) + n (from second R) = 2n + 2. Given that [X] has 6 carbon atoms: 2n + 2 = 6 2n = 4 n = 2 So, R is an alkyl group with 2 carbon atoms, i.e., R = C2H5- (ethyl group).

Identifying the compounds:

  • [C] (Carboxylic acid): R-COOH = C2H5-COOH = CH3CH2COOH (Propanoic acid)
  • [B] (Alcohol): R-CH2-OH = C2H5-CH2-OH = CH3CH2CH2OH (Propan-1-ol)
  • [X] (Ester): R-COO-CH2-R = C2H5-COO-CH2-C2H5 = CH3CH2COOCH2CH2CH3 (Propyl propanoate)

Verification:

  • Molecular formula of Propyl propanoate (CH3CH2COOCH2CH2CH3): C6H12O2. (Matches)
  • Hydrolysis: CH3CH2COOCH2CH2CH3 + H2O →\rightarrow CH3CH2COOH (Propanoic acid) + CH3CH2CH2OH (Propan-1-ol). (Matches [C] and [B])
  • Oxidation: CH3CH2CH2OH (Propan-1-ol) →Jones reagent\xrightarrow{\text{Jones reagent}} CH3CH2COOH (Propanoic acid). (Matches [C])
  • Dehydration: 2 CH3CH2COOH →P2O5, Δ\xrightarrow{\text{P2O5, } \Delta} (CH3CH2CO)2O (Propanoic anhydride). (Matches)

Comparing with options: A. CH3-COO-(CH2)3-CH3 (Butyl acetate): Hydrolysis yields acetic acid and butan-1-ol. Oxidation of butan-1-ol yields butanoic acid, not acetic acid. (Incorrect) B. CH3-COO-C-(CH3)3 (tert-Butyl acetate): Hydrolysis yields acetic acid and tert-butyl alcohol. tert-Butyl alcohol is a tertiary alcohol and does not oxidize to a carboxylic acid under these conditions. (Incorrect) C. CH3-COO-CH2-CH-(CH3)2 (Isobutyl acetate): Hydrolysis yields acetic acid and isobutyl alcohol. Oxidation of isobutyl alcohol yields isobutyric acid, not acetic acid. (Incorrect) D. C2H5-COO-(CH2)2-CH3 (Propyl propanoate): This is CH3CH2COOCH2CH2CH3. Hydrolysis yields propanoic acid and propan-1-ol. Oxidation of propan-1-ol yields propanoic acid. All conditions are met. (Correct)