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प्रश्न
Account for the following:
pKb of aniline is more than that of methylamine.
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उत्तर १
The one which has less basicity has more pKb. The pKb of aniline is more than that of methylamine because aniline has five resonance structures, due to which the unshared electron pair of the nitrogen atom present in it gets delocalized on the benzene ring. This reduces the electron density and aniline does not donate electrons; i.e., the basicity of aniline is less.
On the other hand, the presence of a methyl group in methylamine increases the +I effect, due to which the electron density on the nitrogen atom increases and it readily donates electrons, i.e., methylamine is more basic. Therefore, the pKb of aniline is more than that of methylamine.
उत्तर २
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 CH3NH2 (+I) effect of CH3 increases the electron density on the N atom. Therefore, aniline is a weaker base than methylamine, and hence its pKb value is higher than that of methylamine.
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संबंधित प्रश्न
Which among the following molecular formulae represents urotropine?
(a) C6H12N4
(b) C6H24H4
(c) C6H12N4O2
(d) C6H24N4O2
Write the IUPAC name of the following compound and classify it as primary, secondary and tertiary amine.
CH3NHCH(CH3)2
Write the IUPAC name of the following compound and classify it as primary, secondary and tertiary amine.
(CH3)3CNH2
Write the IUPAC name of the following compound and classify it as primary, secondary and tertiary amine.
m−BrC6H4NH2
Give one chemical test to distinguish between the following pair of compounds.
Methylamine and dimethylamine
Give one chemical test to distinguish between the following pair of compounds.
Secondary and tertiary amines
Give one chemical test to distinguish between the following pair of compounds.
Ethylamine and aniline
Account for the following:
Ethylamine is soluble in water, whereas aniline is not.
How will you convert ethanoic acid into methanamine?
How will you convert methanol to ethanoic acid?
How will you convert methanamine into ethanamine?
Accomplish the following conversion:
Aniline to benzyl alcohol
Complete the following reaction:
\[\ce{C6H5N2Cl + C2H5OH ->}\]
Complete the following reaction:
\[\ce{C6H5NH2 + Br2 (aq) ->}\]
Complete the following reaction:
\[\ce{C6H5N2Cl ->[(i) HBF4][(ii) NaNO2/Cu, \Delta]}\]
Give reasons Although –NH2 is o/p directing group, yet aniline on nitration gives a significant amount of m-nitroaniline
The following amine is called as:
Identify the incorrect IUPAC name.
Do the following conversions in not more than two steps:
\[\begin{array}{cc}
\ce{CH3CN to CH3 - C - CH3}\\
\phantom{...........}||\\
\phantom{...........}\ce{O}
\end{array}\]
