Which of the following are stronger acids than phenol (pKa 10.0) in water?

A $p - O X_{2} N - C X_{6} H X_{4} - OH$
Bcyclohexanol
C $C X_{6} H X_{5} COOH$
D $HC \equiv CH$

Answer: A, C

Phenol has pKa 10.0. 4-Nitrophenol (7.15) is stronger because the nitro group stabilises the phenoxide by -M and -I effects. Benzoic acid (4.20) is stronger because its carboxylate is resonance stabilised over two oxygens. Cyclohexanol (about 16) and ethyne (25) are weaker. So options 1 and 3 are correct.

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Which of the following are stronger acids than phenol (pKa 10.0) in water?

Answer: A, C

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