Why is the $pK_b$ of aniline greater than that of methylamine?
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Solution and Explanation
- Aniline has a phenyl group ($–C_6H_5$), which withdraws electrons through resonance, reducing the electron density on nitrogen and making it a weaker base. Hence, the $pK_b$ of aniline is greater than that of methylamine.
Top Questions on Amines
- Why ammonolysis of alkyl halides is not a good method to prepare pure amines?
- Arrange the following in the increasing order of their basicity in an aqueous solution:
$\text{(CH}_3\text{)}_3\text{N}, \ \text{(CH}_3\text{)}_2\text{NH}, \ \text{NH}_3, \ \text{CH}_3\text{NH}_2$ - Assertion (A): Aromatic primary amines cannot be prepared by Gabriel Phthalimide synthesis.
Reason (R): Ary1 halides do not undergo nucleophilic substitution reaction with the anion formed by phthalimide. For the reaction sequence given below, the correct statement(s) is(are):
Amines have a lone pair of electrons on the nitrogen atom, due to which they behave as Lewis bases. Greater the value of \( K_b \) or smaller the value of \( pK_b \), stronger is the base. Amines are more basic than alcohols, ethers, esters, etc. The basic character of aliphatic amines should increase with the increase of alkyl substitution. However, it does not occur in a regular manner, as a secondary aliphatic amine is unexpectedly more basic than a tertiary amine in aqueous solutions. Aromatic amines are weaker bases than ammonia and aliphatic amines. Electron-releasing groups such as \( -CH_3 \), \( -NH_2 \), etc., increase the basicity, while electron-withdrawing substituents such as \( -NO_2 \), \( -CN \), halogens, etc., decrease the basicity of amines. The effect of these substituents is more pronounced at the para-position than at the meta-position.
Arrange the following in increasing order of their basic character. Give reason:
Questions Asked in CBSE CLASS XII exam
Bittu and Chintu were partners in a firm sharing profit and losses in the ratio of 4:3. Their Balance Sheet as at 31st March, 2024 was as
On $1^{\text {st }}$ April, 2024, Diya was admitted in the firm for $\frac{1}{7}$ share in the profits on the following terms:
- New profit sharing ratio between Bittoo, Chintoo and Diya will be $3:3:1$.
- Fixed Assets were found to be overvalued by ₹ 1,40,000.
- Creditors were paid ₹ 4,20,000 in full settlement.
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Prepare Revaluation Account and Partners' Capital Accounts.
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\(\text{E\(^\circ_{\text{Au}^{3+}/\text{Au}} = +1.5 V, E\)\(^\circ_{\text{Ca}^{2+}/\text{Ca}} = -2.87 V\)}\)
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