The stability of carbanions in the following:

Options

A. `iv gt ii gt iii gt i`
B. `igt iii gt ii gt iv`
C. `i gt ii gt iii gt iv`
D. `ii gt iii gt iv gt i`

Answer

C

Explanation

The stability of the carbanion decreases as the electronegativity of the carbon carrying the-ve charge decreases or the hybridization of the carbon carrying the -ve charge changes from `sp -sp^2 - sp^3`. Thus, `RC -= C^(-)` (i) is the most stable while `R_3C - CH_2^(-)` (iv) is the least stable carbanion. The carbona atom carrying the -ve charge in both `C_6H_5^(-) and R_2 C = CH^(-)" is " sp^2`- hybridized. Out of these two, `R_2C = CH^(-)` (iii) is less stable than `C_6H_5^(-)` (ii) due to +I effect of the two R groups. Thus, teh overall stability decreases in the order : (i) > (ii) > (iii) > (iv), ie, option (C) is correct.