Identification of Reaction Sequence Producing Dicarboxylic Acid As Major Product

To determine which reaction sequence yields a dicarboxylic acid as the major product, we analyze each option step-by-step:

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Option (A):

1. Nucleophilic Substitution: Reaction of 2-chloroethanol ($\text{HO-CH}_2\text{-CH}_2\text{-Cl}$) with $\text{NaCN}$ involves an $\text{S}_\text{N}2$ displacement of the chloride ion by the cyanide nucleophile ($\text{CN}^-$): $\text{HO-CH}_2\text{-CH}_2\text{-Cl} \xrightarrow{\text{NaCN}} \text{HO-CH}_2\text{-CH}_2\text{-CN}$

2. Hydrolysis: Basic hydrolysis ($\text{HO}^-, \text{H}_2\text{O}$) followed by acid workup ($\text{H}_3\text{O}^+$) hydrolyzes the nitrile group ($-\text{CN}$) into a carboxylic acid group ($-\text{COOH}$): $\text{HO-CH}_2\text{-CH}_2\text{-CN} \xrightarrow[\text{(iii) }\text{H}_3\text{O}^+]{\text{(ii) }\text{HO}^-, \text{H}_2\text{O}} \text{HO-CH}_2\text{-CH}_2\text{-COOH}$

• Product: $3$-hydroxypropanoic acid, which is a monocarboxylic acid.

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Option (B):

• Mild Oxidation: Bromine water ($\text{Br}_2, \text{H}_2\text{O}$) is a mild oxidizing agent that selectively oxidizes the aldehyde group ($-\text{CHO}$) of D-glucose to a carboxylic acid group ($-\text{COOH}$), leaving the primary alcohol group ($-\text{CH}_2\text{OH}$) intact: $\text{CHO-(CHOH)}_4\text{-CH}_2\text{OH} \xrightarrow{\text{Br}_2, \text{H}_2\text{O}} \text{COOH-(CHOH)}_4\text{-CH}_2\text{OH}$

• Product: D-gluconic acid, which is a monocarboxylic acid. (Note: Oxidation to a dicarboxylic acid such as D-saccharic acid would require a stronger oxidant like concentrated $\text{HNO}_3$).

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Option (C):

1. Dehydrohalogenation ($\text{E2}$ Elimination): Treatment of bromocyclohexane with alcoholic potassium hydroxide ($\text{KOH, EtOH}$) undergoes $\text{E2}$ elimination to form cyclohexene: $\text{Cyclohexyl bromide} \xrightarrow{\text{KOH, EtOH}} \text{Cyclohexene}$

2. Oxidative Cleavage: Heating cyclohexene with acidic potassium permanganate ($\text{KMnO}_4, \text{H}_2\text{SO}_4, \Delta$) leads to the oxidative cleavage of the double bond. Each $sp^2$ carbon of the alkene ($=\text{CH}-$) is fully oxidized to a carboxylic acid group ($-\text{COOH}$): $\text{Cyclohexene} \xrightarrow{\text{KMnO}_4, \text{H}_2\text{SO}_4, \Delta} \text{HOOC-CH}_2\text{-CH}_2\text{-CH}_2\text{-CH}_2\text{-COOH}$

• Product: Hexanedioic acid (Adipic acid), which contains two carboxylic acid groups and is a dicarboxylic acid.

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Option (D):

• Jones Oxidation: Chromic acid ($\text{H}_2\text{CrO}_4$) selectively oxidizes the primary alcohol group ($-\text{CH}_2\text{OH}$) to a carboxylic acid group ($-\text{COOH}$), while the ketone functional group remains unaffected: $\text{(CH}_3)_2\text{CH-C(=O)-CH(CH}_3)\text{-CH}_2\text{OH} \xrightarrow{\text{H}_2\text{CrO}_4} \text{(CH}_3)_2\text{CH-C(=O)-CH(CH}_3)\text{-COOH}$

• Product: A keto-carboxylic acid, which is a monocarboxylic acid.

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Conclusion:

The reaction sequence in Option (C) produces hexanedioic acid (adipic acid), a dicarboxylic acid, as the major product.

Correct Answer: (C)