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Arrange the following compounds in incre...

Arrange the following compounds in increasing order of boiling point :
Prpane-1-ol, butan-1-ol, butan-2-ol, pentan-1-ol

A

Propan-1-ol,butan-2-ol, butan-1-ol,pentan-1-ol

B

Propan-1-ol,butan-1-ol, butan-2-ol,pentan-ol

C

pentan-1-,butan-2-ol,butan-1-ol,propan-1-ol

D

pentan-1-l,butan-1-ol, butan-2-,ol, propan-1-ol

Text Solution

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The correct Answer is:
To arrange the compounds propane-1-ol, butan-1-ol, butan-2-ol, and pentan-1-ol in increasing order of boiling points, we need to consider the factors that influence boiling points in alcohols, such as molecular weight, branching, and hydrogen bonding. ### Step-by-Step Solution: 1. **Understand the Structure of Each Compound**: - **Propane-1-ol (C3H8O)**: A straight-chain alcohol with three carbon atoms. - **Butan-1-ol (C4H10O)**: A straight-chain alcohol with four carbon atoms. - **Butan-2-ol (C4H10O)**: A branched alcohol with four carbon atoms. - **Pentan-1-ol (C5H12O)**: A straight-chain alcohol with five carbon atoms. 2. **Consider Molecular Weight**: - Generally, as the molecular weight increases, the boiling point also increases. Here, the molecular weights are: - Propane-1-ol: 60 g/mol - Butan-1-ol: 74 g/mol - Butan-2-ol: 74 g/mol (same as butan-1-ol) - Pentan-1-ol: 88 g/mol 3. **Analyze the Effect of Branching**: - In alcohols, branching typically lowers the boiling point due to a decrease in surface area, which reduces the strength of van der Waals forces. - Butan-2-ol is branched, while butan-1-ol is straight-chain. Therefore, butan-2-ol will have a lower boiling point than butan-1-ol. 4. **Compare the Boiling Points**: - Propane-1-ol has the lowest molecular weight and will have the lowest boiling point. - Butan-2-ol, being branched, will have a lower boiling point than butan-1-ol. - Butan-1-ol has a higher boiling point than butan-2-ol due to its straight-chain structure. - Pentan-1-ol, with the highest molecular weight, will have the highest boiling point. 5. **Final Order**: - Arranging them in increasing order of boiling points gives: - Propane-1-ol < Butan-2-ol < Butan-1-ol < Pentan-1-ol ### Conclusion: The final increasing order of boiling points is: **Propane-1-ol < Butan-2-ol < Butan-1-ol < Pentan-1-ol**
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