Question

Arrange the following carbanions in the order of their increasing stability.
i) ${H_3}C - C \equiv {C^ - }$
ii) $H - C \equiv {C^ - }$
iii) ${H_3}C - C{H_2}$

Answer 1

We should firstly know about the carbanions . we must know that the sp hybridised carbon atom is more electronegative than sp3 hybridised carbon atom and this will further accommodate the negative charge more efficiently.

Complete step by step answer:
Firstly we will discuss the carbanions so they are the anions in which the carbon is trivalent and bears a formal negative charge. Further discussing more about them we come to know that carbanions have a concentration of electron density at the negatively charged carbon, which reacts efficiently with different electrophiles of different strengths.
Further we must know that the stability order decreases as we move from the primary to the tertiary anion because due to +I effect of the methyl groups as there is an increased intensity of negative charge on the central carbon of the tertiary carbanion which further makes it unstable.
Moreover we must know that the sp hybridised carbon atom is more electronegative than sp3 hybridised carbon atom and this will further accommodate the negative charge more efficiently. Further we can say that when the methyl group is there then it increases the intensity of negative charge and therefore it leads to further destabilisation of the carbanion. We can further arrange the above carbanions so further it can be arranged as:
(ii)>(i)>(iii)

Note: We must know the hybridisation of the charge bearing atom. The greater the s- character of the charge bearing atom, the more stable the anion. Also we must know that the carbanions are formed as a reactive intermediate and are further used in the elimination reaction.