The correct order of basic strength of the following molecules is:
(A) \(\text{C}_6\text{H}_4\text{NH}_2\text{O}\)
(B) \(\text{C}_6\text{H}_4\text{NH}_2\text{MeO}\)
(C) \(\text{C}_6\text{H}_4\text{NH}_2\text{NO}_2\)
(D) \(\text{C}_6\text{H}_4\text{NH}_2\text{CH}_3\)
(A) \(\text{C}_6\text{H}_4\text{NH}_2\text{O}\)
(B) \(\text{C}_6\text{H}_4\text{NH}_2\text{MeO}\)
(C) \(\text{C}_6\text{H}_4\text{NH}_2\text{NO}_2\)
(D) \(\text{C}_6\text{H}_4\text{NH}_2\text{CH}_3\)
Show Hint
- A$ >$ B $>$ C $>$ D
- B $>$ C $>$ D $>$ A
- D $>$ B $>$ A $>$ C
- B $>$ A $>$ C $>$ D
The Correct Option is D
Solution and Explanation
To determine the basic strength of the given molecules, we need to consider the electron-donating and electron-withdrawing effects of substituents on the phenyl group.
- (A): \(\text{C}_6\text{H}_4\text{NH}_2\text{O}\) (Hydroxyl group is an electron-donating group, which increases the basicity of the amine group.)
- (B): \(\text{C}_6\text{H}_4\text{NH}_2\text{MeO}\) (Methoxy group is a strong electron-donating group, which further increases the basicity of the amine group.)
- (C): \(\text{C}_6\text{H}_4\text{NH}_2\text{NO}_2\) (Nitro group is a strong electron-withdrawing group, which decreases the basicity of the amine group.)
- (D): \(\text{C}_6\text{H}_4\text{NH}_2\text{CH}_3\) (Methyl group is a weak electron-donating group, but its effect is weaker than the hydroxyl or methoxy group.) The order of basic strength is determined by the electron-donating ability of the substituent groups. Therefore, the order is: \[ \text{B}>\text{A}>\text{D}>\text{C} \] Thus, the correct order is \( B>A>C>D \), which corresponds to option (4).
Top Questions on Amines
- Which of the following is a primary amine?
- The product B formed in the following reaction sequence is: $$ {C}_6{H}_5{CN} \xrightarrow{{HCl}} (A) \xrightarrow{{AgCN}} (B) $$
- Identify correct statements: (A) Primary amines do not give diazonium salts when treated with \({NaNO}_2\) in acidic condition.
(B) Aliphatic and aromatic primary amines on heating with \({CHCl}_3\) and ethanolic \({KOH}\) form carbylamines.
(C) Secondary and tertiary amines also give carbylamine test.
(D) Benzenesulfonyl chloride is known as Hinsberg’s reagent.
(E) Tertiary amines react with benzenesulfonyl chloride very easily.
Choose the correct answer from the options given below: 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.
(a) Arrange the following in increasing order of their basic character. Give reason:
\[ \includegraphics[width=0.5\linewidth]{ch29i.png} \]- Amines have a lone pair of electrons on nitrogen atom due to which they behave as Lewis base. 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. But 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 at the p₊ than at m₋ position.
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