Question

Which of the following compound has the highest basic strength?

• A.
• B.
• C.
• D. All have equal basic strength.

Answer 1

The correct option is B

$\text{Basic strength}\propto \frac{1}{\text{Stability of anion}}$

In case of (b) , there is no delocalisation of negative charge, so it is the least stable species and the most basic.
Between (a) and (c) :
In (a) there is cross conjugation as compared to (c) where there is extended conjugation (as shown below).
So, (c) is the more stable species as comapred to (a) and thus the least basic.