Question

The decreasing order of basic strength of the given compounds is :

• A. C > B > D > A
• B. C > B > A > D
• C. A > B > D > C
• D. A > B > C > D

Answer 1

The correct option is B C > B > A > D

Between (b) and (c)
In (c) there are two methyl groups attached to nitrogen that show +I effect, whereas in (b) there is only one methyl group attached.
More the number of alkyl groups attached , more is +I effect shown, and greater is the electron density on nitrogen. So basic strength of (c) is more than (b)
In (a) i.e. aniline, there are no such alkyl groups attached, so it is less basic than (b) and (c).
(d) is least basic due to Steric Inhibition of Protonation (SIP).
Steric Inhibition of Protonation (SIP) :After protonation of ortho substituted aniline, the conjugate acid becomes destabilised due to steric hindrance
Hence, ortho substituted aniline is less basic than aniline