Heating of alkanes with fuming sulphuric acid or oleum at high temperature, which forms sulphonic acid, is called

Options

A. Nitration
B. Halogenation
C. Sulphonation
D. Oxidation

Answer

To solve the question, we need to identify the process that occurs when alkanes are heated with fuming sulfuric acid or oleum at high temperatures, resulting in the formation of sulfonic acid.

### Step-by-Step Solution:

1. **Understanding the Reactants**:
- Alkanes are saturated hydrocarbons with the general formula CnH2n+2. Examples include methane (CH4), ethane (C2H6), and propane (C3H8).
- Fuming sulfuric acid (H2SO4) is a concentrated form of sulfuric acid that contains excess SO3. Oleum is a solution of SO3 in sulfuric acid, often represented as H2SO7.

2. **Reaction Conditions**:
- The reaction occurs at high temperatures, which is essential for the reaction to proceed effectively.

3. **Mechanism of Reaction**:
- When alkanes are treated with fuming sulfuric acid or oleum, the alkane undergoes a sulfonation reaction.
- The high temperature causes the oleum to dissociate into reactive species, including sulfur trioxide (SO3), which can then react with the alkane.

4. **Formation of Sulfonic Acid**:
- The product of this reaction is an alkyl sulfonic acid. This occurs when the SO3 group is introduced into the alkane, resulting in the formation of a sulfonic acid (R-SO3H), where R represents the alkyl group derived from the alkane.

5. **Naming the Process**:
- The overall process of introducing a sulfonic acid group into an alkane through the reaction with fuming sulfuric acid or oleum is called **sulfonation**.

### Final Answer:
The heating of alkanes with fuming sulfuric acid or oleum at high temperature, which forms sulfonic acid, is called **sulfonation**.