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Choose the correct statements. I.In the...

Choose the correct statements.
I.In the case of primary, secondary and tertiary amines, the basic strength depends on the extent of hydrogen bonding in the protonated amines
II. The presence of group like `-OCH_3` and - `CH_3` increase the basic strength of amines
III. The presence of group like `- NO_2, - CN` and halogens reduces the basic strength of amines

A

Only I

B

II and III

C

I and III

D

All of these

Text Solution

AI Generated Solution

The correct Answer is:
To solve the question, we need to evaluate each of the statements regarding the basic strength of amines and determine their correctness. ### Step-by-Step Solution: 1. **Statement I: "In the case of primary, secondary and tertiary amines, the basic strength depends on the extent of hydrogen bonding in the protonated amines."** - **Analysis**: This statement is true. The basic strength of amines is influenced by the ability to form hydrogen bonds when they are protonated. Secondary amines can form more hydrogen bonds compared to primary amines, which makes them more basic. Tertiary amines, while they can also be basic, do not participate in hydrogen bonding as effectively as secondary amines due to steric hindrance. - **Conclusion**: **True** 2. **Statement II: "The presence of groups like -OCH₃ and -CH₃ increase the basic strength of amines."** - **Analysis**: This statement is also true. Groups like -OCH₃ (methoxy) and -CH₃ (methyl) are electron-donating groups. They increase the electron density on the nitrogen atom of the amine, making it more capable of accepting protons, thus increasing the basic strength. - **Conclusion**: **True** 3. **Statement III: "The presence of groups like -NO₂, -CN and halogens reduces the basic strength of amines."** - **Analysis**: This statement is true as well. Groups like -NO₂ (nitro), -CN (cyano), and halogens are electron-withdrawing groups. They decrease the electron density on the nitrogen atom, making it less capable of accepting protons, thus reducing the basic strength of the amines. - **Conclusion**: **True** ### Final Conclusion: All three statements are correct.
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Amines are basic in nature due to the presence of lone pair of electrons on N atom of -NH_(2) group. The basic strength of amines can be expressed by their dissociation constant, K_(b) or pK_(b) . RNH_(2) + H_(2) to R NH_(3)^(+) + OH^(-) K_(b) = ([RHH_(3)^(+)][OH^(-)])/([RNH_(2)]) and pK_(b) = -log K_(b) Greater the K_(b) value or smaller the pK_(b) value, more is the basic strength of amine. Aliphatic amines are stronger bases than ammonia due to the electron releasing effect of alkyl groups. The basic strength among amines decreases as : 2^(@) gt 1^(@) gt 3^(@) Aryl amines such as aniline are less basic than aliphatic amines due to the involvement of lone pair of electrons on N atom with the resonance in benzene. In derivatives of aniline, the electron releasing groups increase the basic strength while electron withdrawing groups decrease the basic strength. The base weakening effect of electron withdrawing group and base strengthening effect of electron releasing group is more marked at p-position than at m-position. Every o- substituted aniline is less basic than aniline due to ortho effect. Which of the following group does not decrease the basic strength of aniline ?

Amines are basic in nature due to the presence of lone pair of electrons on N atom of -NH_(2) group. The basic strength of amines can be expressed by their dissociation constant, K_(b) or pK_(b) . RNH_(2) + H_(2) to R NH_(3)^(+) + OH^(-) K_(b) = ([RHH_(3)^(+)][OH^(-)])/([RNH_(2)]) and pK_(b) = -log K_(b) Greater the K_(b) value or smaller the pK_(b) value, more is the basic strength of amine. Aliphatic amines are stronger bases than ammonia due to the electron releasing effect of alkyl groups. The basic strength among amines decreases as : 2^(@) gt 1^(@) gt 3^(@) Aryl amines such as aniline are less basic than aliphatic amines due to the involvement of lone pair of electrons on N atom with the resonance in benzene. In derivatives of aniline, the electron releasing groups increase the basic strength while electron withdrawing groups decrease the basic strength. The base weakening effect of electron withdrawing group and base strengthening effect of electron releasing group is more marked at p-position than at m-position. Every o- substituted aniline is less basic than aniline due to ortho effect. Which of the following statement is not correct?