Question 4

(A) Nucleophilic substitution of chloride by cyanide followed by hydrolysis results in the formation of 3-hydroxypropanoic acid ($HO-CH_2-CH_2-COOH$), which is a monocarboxylic acid.

(B) Oxidation of glucose with bromine water ($Br_2/H_2O$) selectively oxidizes the terminal aldehyde group to a carboxylic acid group, producing gluconic acid ($COOH-(CHOH)_4-CH_2OH$), which is a monocarboxylic acid.

(C) Bromocyclohexane undergoes dehydrohalogenation with $KOH/EtOH$ to form cyclohexene. Vigorous oxidation of cyclohexene with hot acidic $KMnO_4$ ($KMnO_4, H_2SO_4, \Delta$) cleaves the double bond to form adipic acid ($HOOC-(CH_2)_4-COOH$), which is a dicarboxylic acid.

(D) Reaction of the keto-alcohol 4-hydroxy-3-methylbutan-2-one with $H_2CrO_4$ (Jones reagent) oxidizes the primary alcohol group to a carboxylic acid group while the ketone remains unchanged, resulting in a keto-acid (monocarboxylic acid).

Therefore, reaction sequence (C) is the only one that produces a dicarboxylic acid.