WBJEE · Chemistry · General Organic Chemistry

The exact order of acidity of the compounds p-nitrophenol, acetic acid, acetylene and ethanol is

A p-nitrophenol \( < \) acetic acid \( < \) acetylene \( < \) ethanol
B acetic acid \( < \mathrm{p}-\) nitrophenol \( < \) acetylene \( < \) ethanol
C acetylene \( < \mathrm{p}\)-nitrophenol \( < \) ethanol \( < \) acetic acid
D acetylene \( < \) ethanol \( < \) p-nitrophenol \( < \) acetic acid

Verified Solution

Answer & Solution

Correct Answer

(D) acetylene \( < \) ethanol \( < \) p-nitrophenol \( < \) acetic acid

Step-by-step Solution

Detailed explanation

Acetic acid is most acidic as its conjugte base has equivalent Resonating structure followed by para-nitrophenol. Ethanol is less acidic then para-nitrophenol as conjugate base of p-nitrophenol is resonance stablized but not ethoxide…

Apply the relevant identity from the chapter and substitute the values established in the previous step, keeping the original constraint in view.

Use the simplified expression to isolate the unknown, then plug the result back into the question setup to confirm the working is internally consistent.

Cross-check against a boundary or limiting case. Both the dimensional balance and the qualitative behaviour at the extreme should agree with the candidate answer.

Combine the steps above to identify the correct option. The remaining choices each fail at least one of the consistency, dimensional, or boundary checks.

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