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N-butylamine (I), diethylamine (II) and ...

N-butylamine (I), diethylamine (II) and N,N-dimethyl ethylamine(III) have the same molar mass. The increasing order of their boiling point is:

A

`III lt II lt I`

B

`I lt II lt III`

C

`II lt III lt I`

D

`II lt I lt III`

Text Solution

AI Generated Solution

The correct Answer is:
To determine the increasing order of boiling points for N-butylamine (I), diethylamine (II), and N,N-dimethyl ethylamine (III), we need to consider the molecular structures and the ability of each compound to form hydrogen bonds. ### Step-by-Step Solution: 1. **Identify the Structures and Molecular Formulas**: - **N-butylamine (I)**: The structure is CH3-CH2-CH2-CH2-NH2. It has one amine group (NH2) which can participate in hydrogen bonding. - **Diethylamine (II)**: The structure is CH3-CH2-NH-CH2-CH3. It has one amine group (NH) which can also participate in hydrogen bonding, but it has fewer hydrogen atoms available for bonding compared to N-butylamine. - **N,N-dimethyl ethylamine (III)**: The structure is CH3-N(CH3)-CH2-CH3. It has two methyl groups attached to the nitrogen and one ethyl group, but no hydrogen atoms directly bonded to the nitrogen, which means it cannot form hydrogen bonds. 2. **Analyze Hydrogen Bonding**: - **N-butylamine (I)** can form multiple hydrogen bonds due to the presence of two hydrogen atoms attached to the nitrogen. - **Diethylamine (II)** can form hydrogen bonds, but only one hydrogen is available for bonding. - **N,N-dimethyl ethylamine (III)** cannot form hydrogen bonds since there are no hydrogen atoms bonded to the nitrogen. 3. **Determine the Boiling Points**: - Compounds with stronger hydrogen bonding typically have higher boiling points. Therefore, we can rank the compounds based on their ability to form hydrogen bonds: - **N-butylamine (I)** has the highest boiling point due to the ability to form the most hydrogen bonds. - **Diethylamine (II)** has a lower boiling point than N-butylamine but higher than N,N-dimethyl ethylamine. - **N,N-dimethyl ethylamine (III)** has the lowest boiling point due to the absence of hydrogen bonding. 4. **Conclusion**: - The increasing order of boiling points is: - N,N-dimethyl ethylamine (III) < Diethylamine (II) < N-butylamine (I) ### Final Answer: The increasing order of boiling points is: N,N-dimethyl ethylamine (III) < Diethylamine (II) < N-butylamine (I).
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