Arrange the following: i. In increasing order of solubility in water: C6H5NH2, (C2H5)2NH, C2H5NH2 ii. In incre

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Q. Arrange the following: i. In increasing order of solubility in water: C6H5NH2, (C2H5)2NH, C2H5NH2 ii. In increasing order of basic strength:

(a) aniline, p-toluidine and p-nitroaniline;

(b) C6H5NH2, C6H5NHCH3, p-Cl-C6H4-NH2
iii. In decreasing order of basic strength in gas phase: (C2H5)2NH, (C2H5)3N, C2H5NH2 and NH3
iv. In increasing order of boiling point: C2H5OH, (CH3)2NH, C2H5NH2
v. In decreasing order of pKb values: C2H5NH2, C6H5NHCH3, (C2H5)2NH and CH3NH2
vi. In increasing order of basic strength: C6H5NH2, C6H5N(CH3)2, (C2H5)2NH and CH3NH2
vii. In decreasing order of basic strength: CH3CH2NH2, p-O2N-C6H4-NH2, C6H5NH2, CH3-NH2

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Step 1. i. Solubility falls as hydrophobic bulk rises and rises with H-bond-donor capacity: aniline (large aromatic ring, least soluble) < diethylamine (bulkier dialkyl, moderately soluble) < ethylamine (small, most soluble).

Step 2. ii(a). Basicity order for substituted anilines: the electron-withdrawing -NO2 group (p-nitroaniline) is weakest; plain aniline is intermediate; the electron-donating -CH3 (p-toluidine) is strongest -- increasing order p-nitroaniline < aniline < p-toluidine.

Step 3. ii(b). p-Cl-C6H4-NH2 (electron-withdrawing halogen, weakest) < C6H5NH2 (aniline, baseline) < C6H5NHCH3 (N-methylaniline, extra +I donation from the N-methyl slightly raises basicity above plain aniline, per the unit's own pKb data, 9.30 vs 9.376).

Step 4. iii. Gas-phase basicity (no solvation to complicate matters) follows the +I-effect directly: more alkyl substitution on nitrogen means more donation, so (C2H5)3N > (C2H5)2NH > C2H5NH2 > NH3, decreasing steadily as substitution falls.

Step 5. iv. Boiling point: among the amines, the secondary amine (CH3)2NH boils lower than the primary C2H5NH2 (fewer N-H for hydrogen bonding), and the alcohol C2H5OH boils highest of all three (O-H hydrogen bonds are stronger than N-H ones) -- increasing order (CH3)2NH < C2H5NH2 < C2H5OH.

Step 6. v. Decreasing pKb (i.e. simply ranking the numeric pKb values from largest to smallest, per the unit's own table): C6H5NHCH3 (9.30) > CH3NH2 (3.38) > C2H5NH2 (3.29) > (C2H5)2NH (3.00). …

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Same / Similar Concept — real previous-year questions on the same or a closely similar concept, not this exact question.

CBSE 2026Set ANNUAL1 markMCQ
$Q. The correct order for basic strength of amines and ammonia is _____.$
(a) $NH_3 > R-NH_2 > R_2NH > R_3N$
(b) $NH_3 > R_3N > R_2NH > R-NH_2$
(c) $NH_3 < R-NH_2 > R_3N > R_2NH$
(d) $NH_3 < R-NH_2 < R_2NH > R_3N$
›Reveal solutionSolution

In aqueous solution, aliphatic amine basicity follows: $R_2NH > R\text{-}NH_2 > R_3N > NH_3$ ; option (d) correctly places $NH_3$ lowest and $R_2NH$ highest.

In the gas phase, increasing alkyl substitution increases basicity purely by the +I (electron-donating) effect, giving $R_3N > R_2NH > RNH_2 > NH_3$ .

However, in aqueous solution basicity also depends on how well the resulting ammonium cation is stabilised by hydrogen bonding with water (solvation). A tertiary amine's ammonium ion ( $R_3NH^+$ ) has only one N–H bond available for hydrogen bonding and also suffers steric hindrance, so it is poorly solvated despite the strong inductive effect of three alkyl groups.

…

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CBSE 2017Set ANNUAL1 markMCQ
$Q. The basic character of amines is due to :$
(a) tetrahedral structure
(b) presence of nitrogen atom
(c) lone pair of electrons on nitrogen atom
(d) high electronegativity of nitrogen
›Reveal solutionSolution

Amines are basic because the nitrogen atom has a readily available lone pair of electrons that can be donated to accept a proton.

In an amine, nitrogen is bonded to carbon and/or hydrogen atoms using three of its five valence electrons in covalent bonds, while the remaining two electrons exist as a lone pair on nitrogen. This lone pair is not tied up in any bond and is available for donation.

…

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Q.Arrange the following:
i. In increasing order of solubility in water: C6H5NH2, (C2H5)2NH, C2H5NH2
ii. In increasing order of basic strength:

Concept understanding — Basicity of Amines

Q.Arrange the following: i. In increasing order of solubility in water: C6H5NH2, (C2H5)2NH, C2H5NH2 ii. In increasing order of basic strength:

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Q.Arrange the following:
i. In increasing order of solubility in water: C6H5NH2, (C2H5)2NH, C2H5NH2
ii. In increasing order of basic strength:

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