When vapours of an alcohol are passed over hot reduced copper, it gives an alkene. The alcohol is

Options

A. Primary
B. Secondary
C. Tertiary
D. None of these

Answer

To solve the question, "When vapours of an alcohol are passed over hot reduced copper, it gives an alkene. The alcohol is?", we need to analyze the behavior of different types of alcohols when they are subjected to dehydrogenation using hot reduced copper.

### Step-by-Step Solution:

1. **Understanding the Process**:
- When alcohol vapors are passed over hot reduced copper, a dehydrogenation reaction occurs. This means that hydrogen (H2) is removed from the alcohol.

2. **Types of Alcohols**:
- Alcohols can be classified into three categories: primary, secondary, and tertiary.

3. **Reactions of Different Alcohols**:
- **Primary Alcohols**:
- When a primary alcohol is treated with hot reduced copper, it typically gets oxidized to form an aldehyde, not an alkene. For example, ethanol (CH3CH2OH) would yield acetaldehyde (CH3CHO) and hydrogen gas (H2).
- **Secondary Alcohols**:
- Secondary alcohols, when subjected to the same conditions, are oxidized to form ketones. For instance, isopropanol (CH3CHOHCH3) would yield acetone (CH3C(=O)CH3) and hydrogen gas (H2).
- **Tertiary Alcohols**:
- Tertiary alcohols do not undergo oxidation to form aldehydes or ketones due to the absence of alpha hydrogens. Instead, they undergo dehydration, leading to the formation of alkenes. For example, tert-butanol (CH3)3COH would dehydrate to form isobutylene (CH2=C(CH3)2) and water (H2O).

4. **Conclusion**:
- Since the question specifies that an alkene is produced, we conclude that the alcohol in question must be a tertiary alcohol.

### Final Answer:
The alcohol is **tertiary alcohol**.