Which of the following gives the correct order of decreasing acidity of the C-H bonds in the compounds below?

A $CH X_{3} NO X_{2} > CH X_{3} COCH X_{3} > CH X_{3} CN > CH X_{3} CH X_{3}$
B $CH X_{3} COCH X_{3} > CH X_{3} NO X_{2} > CH X_{3} CN > CH X_{3} CH X_{3}$
C $CH X_{3} NO X_{2} > CH X_{3} CN > CH X_{3} COCH X_{3} > CH X_{3} CH X_{3}$
D $CH X_{3} CN > CH X_{3} COCH X_{3} > CH X_{3} NO X_{2} > CH X_{3} CH X_{3}$

Answer: A

Approximate pKa values: nitromethane 10.2, acetone 19.3, acetonitrile 25 and ethane about 50. The nitro group stabilises the adjacent carbanion best (resonance onto two oxygens), then the carbonyl group, then the cyano group, while ethane has no stabilising group.

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Which of the following gives the correct order of decreasing acidity of the C-H bonds in the compounds below?

Answer: A

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