Question

A strong base can abstract an $\alpha $ hydrogen from:
A.Amine
B.Alkene
C.Alkane
D.Ketone

Answer 1

Hint: The alpha carbon in organic molecules refers to the first carbon atom that attaches to a functional group. Basically, a base increases the acidity of hydrogen atoms attached to the $\alpha $ carbon of the ketones or aldehydes.

Complete step by step answer:
Alkanes, alkenes and amines contain an electron releasing group. Now, electron releasing groups are an atom or functional group that donates some of its electron density into a conjugated $\pi $ system via resonance or inductive effects. These are also known as electron donating groups.
Basically, the concept of resonance tells us about the polarity induced in a molecule by the reaction between a lone pair of electrons and a pi-bond. It only occurs by the interaction of two pi-bonds in the adjacent atom.
Now, alkane, alkene and amine contain electron releasing groups, so they cannot produce alpha-hydrogen. But aldehydes and ketones are strong electron withdrawing groups and can produce alpha-hydrogen easily.
Moreover, the base ion removes one of the alpha hydrogen from aldehyde and ketones and forms a carbanion or an enolate ion. Further, the acidity of alpha hydrogen is due to the resonance stabilization of enolate ion.

Hence, option D is correct.

Note:
There are two types of resonance effects namely positive resonance effect and negative resonance effect. The positive resonance effect occurs when the groups release electrons to the other molecules by the process of delocalization whereas negative resonance effect occurs when the groups withdraw the electrons from other molecules by the process of delocalization.