Question

Assertion : The order of basic strength in case of methyl substituted and ethyl substituted amines in aqueous state is different.
Reason : Methyl group has stronger inductive effect than ethyl group.

• A. If both assertion and reason are true and reason is the correct explanation of assertion
• B. If both assertion and reason are true but reason is not the correct explanation of assertion
• C. If assertion is true but reason is false
• D. If both assertion and reason are false

Answer 1

Answer: (C)

In aqueous phase, the substituted ammonium cations get stabilised not only by electron releasing effect of alkyl group but also by solvation with water molecules. In case of $-CH_{3}$ group, there is no steric hinderance to $H$-bonding, but in case of bigger groups there is steric hinderance and hence the order changes. In case of methyl substituted amines the order is
$(CH_{3})_{2}NH > CH_{3}NH_{2} > (CH_{3})_{3}N > NH_{3}$
and in ethyl substituted amines
$(C_{2}H_{5})_{2}NH > (C_{2}H_{5})_{3}N > C_{2}H_{5}NH_{2} > NH_{3}$