Which of the following alcohols does not give an aldehyde on oxidation ?

Options

A. Benzyl alcohol
B. Sec. butyl alcohol
C. Allyl alcohol
D. Crotyl alcohol

Answer

To determine which alcohol does not give an aldehyde upon oxidation, we need to analyze the types of alcohols and their oxidation products:

### Step 1: Identify the Types of Alcohols
- **Primary Alcohols (1°)**: These have the general structure R-CH2OH. Upon oxidation, they are converted to aldehydes (R-CHO).
- **Secondary Alcohols (2°)**: These have the structure R1-CHOH-R2. Upon oxidation, they yield ketones (R1-CO-R2).
- **Tertiary Alcohols (3°)**: These have the structure R1-COH-R2-R3. Upon oxidation, they do not produce aldehydes or ketones.

### Step 2: Analyze the Given Alcohols
1. **Benzyl Alcohol (C6H5-CH2OH)**: This is a primary alcohol. Upon oxidation, it gives benzaldehyde (C6H5-CHO), which is an aldehyde.

2. **Secondary Butyl Alcohol (CH3-CH(OH)-CH2-CH3)**: This is a secondary alcohol. Upon oxidation, it gives ketones (specifically, it would yield butan-2-one). Therefore, it does not produce an aldehyde.

3. **Allylic Alcohol (CH2=CH-CH2OH)**: This is a primary alcohol. Upon oxidation, it produces an aldehyde.

4. **Crotyl Alcohol (CH3-CH=CH-CH2OH)**: This is also a primary alcohol. Upon oxidation, it produces an aldehyde.

### Conclusion
From the analysis, the alcohol that does not give an aldehyde upon oxidation is **Secondary Butyl Alcohol** since it is a secondary alcohol and produces a ketone instead.

### Final Answer
**Secondary Butyl Alcohol does not give an aldehyde on oxidation.**

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