Addition of hydrogen to alkene in presence of nickel catalyst is

Options

A. reduction
B. oxidation
C. addition and elimination
D. substitution

Explanation

To solve the question regarding the addition of hydrogen to an alkene in the presence of a nickel catalyst, we can break down the process step by step.

### Step-by-Step Solution:

1. **Understanding the Reaction**:
- The reaction involves the addition of hydrogen (H₂) to an alkene (which is an unsaturated hydrocarbon) in the presence of a nickel catalyst.

**Hint**: Remember that alkenes contain double bonds, which are characteristic of unsaturated hydrocarbons.

2. **Role of the Catalyst**:
- Nickel acts as a catalyst in this reaction. Catalysts are substances that speed up a chemical reaction without being consumed in the process.

**Hint**: Catalysts lower the activation energy of a reaction, making it easier for the reaction to occur.

3. **Conditions of the Reaction**:
- The reaction typically occurs at elevated temperatures, around 200 degrees Celsius, to facilitate the addition of hydrogen.

**Hint**: Temperature can significantly affect the rate of reaction, especially in catalytic processes.

4. **Mechanism of the Reaction**:
- When hydrogen is added to the alkene, the double bond in the alkene is broken. The hydrogen atoms then bond with the carbon atoms that were previously involved in the double bond.

**Hint**: Visualize the breaking of the double bond and the formation of new single bonds with hydrogen.

5. **Formation of the Product**:
- The result of this reaction is a saturated hydrocarbon, meaning that all carbon-carbon bonds are single bonds, and there are no double or triple bonds remaining.

**Hint**: Saturated hydrocarbons are typically more stable than their unsaturated counterparts.

6. **Type of Reaction**:
- This process can be classified as an addition reaction because hydrogen is being added to the alkene. It can also be viewed as a reduction reaction since the addition of hydrogen reduces the degree of unsaturation.

**Hint**: In organic chemistry, addition reactions often involve the conversion of unsaturated compounds to saturated ones.

7. **Conclusion**:
- Therefore, the addition of hydrogen to an alkene in the presence of a nickel catalyst is primarily classified as an **addition reaction**.

**Hint**: Look for keywords in the question that indicate the type of reaction, such as "addition" or "reduction".

### Final Answer:
The addition of hydrogen to an alkene in the presence of a nickel catalyst is called an **addition reaction**.