Assertion : $p K b$ of aniline is more than that of methylamine. Reason: In aniline, the lone pair of electrons on the $N$ atom is delocalized over the benzene ring. As a result, the electron density of nitrogen decreases. In contrast, in ${C H}_{3} {N H}_{2} (+ I)$ effect of ${C H}_{3}$ increases the electron density on the $N$ atom. Therefore, aniline is a weaker base than methylamine and hence its $p K_{b}$ value is higher than that of methylamine.

Both Assertion and Reason are correct and Reason is the correct explanation for Assertion

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Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion

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Assertion is correct but Reason is incorrect

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Both Assertion and Reason are incorrect

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Solution

The correct option is A Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
In aniline, the lone pair of electrons on the N atom is delocalised over the benzene ring.

As a result, the electron density on nitrogen decreases. In contrast, in ${C H}_{3} {N H}_{2} (+ I)$ effect of ${C H}_{3}$ increases the electron density on the N atom.

Therefore, aniline is a weaker base than methylamine and hence its $p K b$ value is higher than that of methylamine.

Option A is correct.

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Similar questions

A : Nitration of aniline can only be done by protecting $- N H_{2}$ group through acetylation.
R : Acetylation of aniline results in the increase of electron density at the benzene ring.

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and

{Al}^{3 +}

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{Al}^{3 +}

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{Mg}^{2 +}

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Q. Read the assertion and reason carefully to mark the correct option out of the options given below:

(a)If both assertion and reason are true and the reason is the correct explanation of the assertion.

(b)If both assertion and reason are true but reason is not the correct explanation of the assertion.

(c)If assertion is true but reason is false.

(d)If assertion is false but reason is true.
Assertion: Ionisation enthalpies for early actinoids are lower than that for early lanthanoids.
Reason: 5f electrons more effectively shielded from the nuclear charge than the 4f electrons
of the corresponding lanthanoids.

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