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Place the following alcohols in decreasi...

Place the following alcohols in decreasing order of rate of dehydration with `H_(2)SO_(4)`.
`CH_(3)CH_(2)CHunderset((1))((OH))CH_(2)CH_(2)CH_(3)`
`(CH_(3))_(2)Cunderset((2))((OH))CH_(2)CH_(2)CH_(3)`
`(CH_(3))_(2)Cunderset((3))((OH))CH(CH_(3))_(2)`
`CH_(3)CH_(2)CHunderset((4))((OH))CH(CH_(3))_(2)`
`CH_(3)CH_(2)CH_(2)underset((5))(CH_(2))CH_(2)CH_(2)OH`

A

`3 gt 2gt 4 gt 5 gt 1`

B

`3 gt 2 gt 4 gt 1 gt 5`

C

`3 gt 2 gt 1 gt 4 gt 5`

D

`3 gt 2 gt 1 gt 5 gt 4`

Text Solution

AI Generated Solution

The correct Answer is:
To determine the order of dehydration rates of the given alcohols with sulfuric acid, we need to analyze the structure of each alcohol and the stability of the alkenes formed after dehydration. ### Step-by-Step Solution: 1. **Identify the Alcohols:** - Alcohol 1: CH₃CH₂CH(OH)CH₂CH₂CH₃ - Alcohol 2: (CH₃)₂C(OH)CH₂CH₂CH₃ - Alcohol 3: (CH₃)₂C(OH)CH(CH₃)₂ - Alcohol 4: CH₃CH₂CH(OH)CH(CH₃)₂ - Alcohol 5: CH₃CH₂CH₂(CH₂)CH₂CH₂OH 2. **Understand the Dehydration Mechanism:** - Dehydration of alcohols occurs via an E2 mechanism, where the alcohol is first protonated by sulfuric acid, making the hydroxyl group a better leaving group. - The stability of the resulting alkene is crucial; more substituted alkenes are more stable and thus form more readily. 3. **Determine the Alkenes Formed:** - **Alcohol 1:** Dehydration leads to CH₃CH₂C(CH₃)=CH₂ (two substituents). - **Alcohol 2:** Dehydration leads to (CH₃)₂C=CH(CH₂CH₃) (three substituents). - **Alcohol 3:** Dehydration leads to (CH₃)₂C=CH(CH₃)₂ (four substituents). - **Alcohol 4:** Dehydration leads to CH₃CH₂C=CH(CH₃)₂ (three substituents). - **Alcohol 5:** Dehydration leads to CH₃CH₂CH=CH₂ (one substituent). 4. **Rank the Stability of the Alkenes:** - Alcohol 3 forms the most stable alkene (four substituents). - Alcohol 2 and Alcohol 4 both form alkenes with three substituents, but Alcohol 2 is tertiary, making it more reactive than the secondary Alcohol 4. - Alcohol 1 forms an alkene with two substituents. - Alcohol 5 forms an alkene with only one substituent. 5. **Order of Dehydration Rates:** - Based on the stability of the alkenes formed, the order of dehydration rates is: - **Alcohol 3 > Alcohol 2 > Alcohol 4 > Alcohol 1 > Alcohol 5** ### Final Answer: The order of the alcohols in decreasing order of rate of dehydration with H₂SO₄ is: **3 > 2 > 4 > 1 > 5**
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