Question

Which of the following compounds does not contain acidic hydrogen $ ? $
(A) Phenol
(B) Methyl amine
(C) Acetic acid
(D) Methyl alcohol

Answer 1

Hint :Acidic hydrogen is a hydrogen atom in an acid that forms a positive ion when the acid dissociates. It has a tendency to be released as $ {H^ + } $ ion. An acid is a substance or compound that releases hydrogen ions ( $ {H^ + } $ ) when placed/ dissolved in water.

Complete Step By Step Answer:
A. Phenol can lose a hydrogen ion and form a phenoxide ion which is more stable than phenol due to the delocalization of the negative charge. Hence phenols are acidic in nature.
B.The electron density around the nitrogen atom in methylamine is greater than the electron density around the nitrogen atom in phenylamine, so the lone pair of electrons on the nitrogen atom are more easily donated to a proton by methylamine than phenylamine. Methylamine is a stronger base.
C. Acetic acid is a weak acid. In an aqueous solution it can donate its proton. if a compound gives proton or $ {H^ + } $ ion on dissociation it is an acid. Hence Acetic acid $ C{H_3}COOH $ is acidic.
D. Methanol ( $ C{H_3}OH $ ) is more acidic than water because its conjugate base methoxide is weaker than water's conjugate base hydroxide. The methyl group slightly takes away electron density from the oxygen atom, unlike the hydrogen in water, which actually contributes more electron distribution.
Hence the correct option is B. Methylamine.

Note :
Note that the $ \beta $ - hydrogen atom of carbonyl compounds is more acidic in nature than $ \alpha $ -hydrogen. Also, high concentrations of hydrogen ions yield a low pH (acidic substances), whereas low levels of hydrogen ions result in a high pH (basic substances). Methanol is also called methyl alcohol, wood alcohol, or wood spirit.