Question

Which among the following amines is most basic in aqueous medium?

• A. $(C_2H_5)_2NH$
• B. $(C_2H_5)_3N$
• C. $C_2H_5NH_2$
• D. $NH_3$
• A. \((CH_3)_2NH\)
• B. \(CH_3NH_2\)
• C. \((CH_3)_3N\)
• D. \(NH_3\)
• A. $(CH$_3$)$_2$NH$
• B. $CH$_3$NH$_2$$
• C. $(CH$_3$)$_3$N$
• D. $NH$_3$$
• A. Conjugation factor
• B. Inductive effect
• C. Solvation effect
• D. Steric hindrance
• A. 2,4-dinitrophenol
• B. NaNO₂ + HCl mixture
• C. HNO₃ + H₂SO₄ mixture
• D. Benzenesulphonyl chloride

Answer 1

The Correct Option is C

In aqueous medium, the basicity of amines is influenced by several factors, including steric hindrance and the ability to stabilize the positive charge on the ammonium ion formed upon protonation.
Primary amine (C₂H₅NH₂) : Has two hydrogen atoms available for bonding, allowing for effective solvation and stabilization when protonated.- Secondary amine ((C₂H₅)₂NH) : Has some steric hindrance but is still relatively basic.- Tertiary amine ((C₂H₅)₃N) : Although it can stabilize a positive charge well, steric hindrance prevents effective interaction with protons in aqueous solution.- Ammonia (NH₃) : Less basic than primary amines.
Thus, in the aqueous medium, the most basic amine is the primary amine, C₂H₅NH₂ .

Answer 2

In aqueous medium, the basicity of amines is influenced by several factors, including steric hindrance and the ability to stabilize the positive charge on the ammonium ion formed upon protonation. The relative basicity of various amines can be explained as follows:

• Primary amine (C₂H₅NH₂): Has two hydrogen atoms available for bonding, allowing for effective solvation and stabilization when protonated. This leads to a higher basicity in aqueous medium.
• Secondary amine ((C₂H₅)₂NH): Has some steric hindrance due to the two ethyl groups, but it remains relatively basic due to its ability to accept protons.
• Tertiary amine ((C₂H₅)₃N): Although it can stabilize a positive charge well, steric hindrance prevents effective interaction with protons in aqueous solution, making it less basic compared to primary and secondary amines.
• Ammonia (NH₃): Less basic than primary amines due to the lack of alkyl groups, which provide electron-donating effects that enhance basicity.

Thus, in aqueous medium, the most basic amine is the primary amine, C₂H₅NH₂. The presence of alkyl groups in primary amines allows for better solvation and protonation, enhancing their basicity.

Answer 3

To determine the least basic amine among the options provided, we analyze the effects of alkyl groups on basicity in aqueous medium:
1. Methylamine (CH₃NH₂) : A primary amine that is relatively basic due to less steric hindrance and effective solvation.
2. Dimethylamine ((CH₃)₂NH) : A secondary amine that is basic, but steric hindrance starts to affect its basicity.
3. Trimethylamine ((CH₃)₃N) : A tertiary amine where steric hindrance is significant, leading to reduced basicity compared to
primary and secondary amines.
4. Ammonia (NH3) : Though not an amine with alkyl groups, it serves as a reference for basicity.
In conclusion, trimethylamine ((CH₃)₃N) is the least basic in aqueous medium due to significant steric hindrance, which limits effective solvation and protonation.

Answer 4

To determine the least basic amine among the options provided, we analyze the effects of alkyl groups on basicity in aqueous medium:

• Methylamine (CH₃NH₂): A primary amine that is relatively basic due to less steric hindrance and effective solvation, allowing for better protonation.
• Dimethylamine ((CH₃)₂NH): A secondary amine where basicity is still strong, but steric hindrance from the two methyl groups begins to affect its reactivity.
• Trimethylamine ((CH₃)₃N): A tertiary amine where steric hindrance is significant, leading to reduced basicity compared to primary and secondary amines. This makes it less effective in interacting with protons in aqueous medium.
• Ammonia (NH₃): Not an amine with alkyl groups, but it serves as a reference for basicity. Its basicity is lower than primary amines due to the lack of alkyl groups that would stabilize the protonated form.

Conclusion: In aqueous medium, trimethylamine ((CH₃)₃N) is the least basic due to significant steric hindrance, which limits effective solvation and protonation.

Answer 5

In the gaseous phase, trimethylamine ((CH₃)₃N) is the most basic amine due to the strong electron-donating effect of the three methyl groups despite its steric hindrance.

Answer 6

In the gaseous phase, trimethylamine ((CH₃)₃N) is the most basic amine due to the strong electron-donating effect of the three methyl groups, which increase the electron density on the nitrogen atom. This makes the nitrogen more likely to donate electrons to a proton, enhancing its basicity.

Despite the presence of steric hindrance from the bulky methyl groups, which can prevent efficient protonation in some environments, trimethylamine still exhibits greater basicity compared to primary and secondary amines in the gaseous phase. This is because the electron-donating groups (methyl groups) play a more significant role in enhancing the nucleophilicity of the nitrogen atom.

In contrast, in aqueous solutions, steric hindrance becomes a more prominent factor, reducing the ability of trimethylamine to interact effectively with protons. As a result, its basicity decreases in comparison to primary amines, such as methylamine (CH₃NH₂).

Overall, while trimethylamine’s steric hindrance can limit its protonation in certain conditions, its strong electron-donating effect in the gaseous phase makes it the most basic amine in that environment.

Answer 7

The basic strength of amines in aqueous medium is influenced by factors such as:

1. Inductive Effect: The electron-donating or withdrawing properties of alkyl groups impact the availability of the nitrogen's lone pair for protonation.
2. Solvation Effect: Better solvation with water molecules enhances basicity by stabilizing the protonated amine.
3. Steric Hindrance: Larger alkyl groups hinder proton access to the nitrogen, reducing basicity.
4. Conjugation Factor: This does not significantly affect the basic strength of amines, as conjugation involves pi bonds and does not influence protonation directly.

Thus, conjugation is not responsible for the basic strength of amines.

Answer 8

The basic strength of amines in aqueous medium is influenced by various factors, each contributing to the overall reactivity of the nitrogen atom in the amine group. These factors include:

1. Inductive Effect: The electron-donating or withdrawing properties of alkyl groups attached to the nitrogen atom significantly affect the availability of the nitrogen's lone pair for protonation. Alkyl groups, which are electron-donating, increase the electron density on nitrogen, enhancing its ability to accept protons and thus increasing basicity.
2. Solvation Effect: The interaction between the amine and water molecules plays a crucial role in determining its basicity. Better solvation of the protonated amine, where water molecules stabilize the positive charge on nitrogen, enhances basicity. More solvation allows for more effective protonation, making the amine more basic.
3. Steric Hindrance: The size of the alkyl groups attached to the nitrogen atom impacts the basicity of amines. Larger alkyl groups create steric hindrance, which prevents efficient protonation by obstructing the approach of protons to the nitrogen atom, thereby decreasing basicity.
4. Conjugation Factor: While conjugation with pi bonds (such as in aniline or other conjugated amines) can influence other chemical properties, it does not significantly affect the basic strength of amines. Conjugation typically involves interactions with p orbitals, which do not directly impact the nitrogen's ability to accept a proton, making it less relevant in determining basicity.

Thus, the conjugation effect does not contribute significantly to the basic strength of amines in aqueous medium, unlike inductive and solvation effects.

Answer 9

Hinsberg's reagent, benzenesulphonyl chloride, is used to differentiate primary, secondary, and tertiary amines based on their reaction products. Primary amines form soluble sulfonamides, secondary amines form sulfonamides that may be soluble or insoluble, and tertiary amines do not react significantly. Thus, benzenesulphonyl chloride is the correct reagent for this identification.

Answer 10

Hinsberg's reagent, which is benzenesulphonyl chloride (C₆H₅SO₂Cl), is a crucial chemical used to differentiate primary, secondary, and tertiary amines based on their distinct reactivity patterns. The reaction outcomes are as follows:

1. Primary Amines: When primary amines react with benzenesulphonyl chloride, they form soluble sulfonamides, which are characterized by their solubility in aqueous solutions. This is due to the ability of the amine group to effectively react and form a stable bond with the sulfonyl group.
2. Secondary Amines: Secondary amines can form soluble or insoluble sulfonamides depending on the conditions, such as the solvent used. The reaction is less straightforward compared to primary amines, and the solubility of the resulting product can vary.
3. Tertiary Amines: Tertiary amines do not react significantly with Hinsberg's reagent, as they lack the required hydrogen atom attached to the nitrogen for the reaction to proceed. As a result, no sulfonamide formation occurs in this case.

Thus, benzenesulphonyl chloride is an effective reagent for distinguishing primary, secondary, and tertiary amines based on the solubility and nature of the products formed.