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Which one of the following reactions does NOT give benzene as the product?
A
Reaction (1) 
B
Reaction (2) 
C
Reaction (3) 
D
Reaction (4) 
Explanation
Hydrolysis of benzenediazonium chloride with warm water yields phenol ($\text{C}_6\text{H}_5\text{OH}$), not benzene.
Detailed Solution
Reaction (1) is decarboxylation of sodium benzoate giving benzene. Reaction (2) is aromatization of n-hexane over $\text{Mo}_2\text{O}_3$ catalyst giving benzene. Reaction (3) is cyclic polymerization of ethyne forming benzene. Reaction (4) is warming benzenediazonium chloride with water, which undergoes nucleophilic substitution to yield phenol: $\text{C}_6\text{H}_5\text{N}_2^+\text{Cl}^- + \text{H}_2\text{O} \xrightarrow{\Delta} \text{C}_6\text{H}_5\text{OH} + \text{N}_2 + \text{HCl}$. Thus, reaction (4) does not yield benzene.