In halogenation process rate of reaction of alkanes with halogens is

Options

A. `F_2gtCl_2gtBr_2gtI_2`
B. `I_2gtBr_2gtCl_2gtF_2`
C. `I_2gtF_2gtCl_2gtBr_2`
D. `F_2gtCl_2gtI_2gtBr_2`

Answer

To determine the rate of reaction of alkanes with halogens during the halogenation process, we need to analyze the bond strengths of the halogen molecules involved. Here's a step-by-step breakdown of the solution:

### Step-by-Step Solution:

1. **Understanding Halogenation**:
- Halogenation is a reaction where alkanes react with halogens (like Cl2, Br2, I2) to form alkyl halides. This reaction typically proceeds via a free radical mechanism.

2. **Identifying Halogens**:
- The common halogens involved in halogenation are fluorine (F2), chlorine (Cl2), bromine (Br2), and iodine (I2).

3. **Bond Strength and Bond Length**:
- The rate of reaction is influenced by the bond strength of the halogen molecules. Generally, the weaker the bond, the easier it is to break, leading to a faster reaction.
- Bond strength is inversely related to bond length: longer bonds are typically weaker.

4. **Analyzing Bond Strengths**:
- **Iodine (I2)**: Has the weakest bond due to its large atomic size and long bond length, making it the most reactive in halogenation.
- **Bromine (Br2)**: Has a stronger bond than iodine but weaker than chlorine and fluorine.
- **Chlorine (Cl2)**: Has a stronger bond than bromine but weaker than fluorine.
- **Fluorine (F2)**: Although fluorine has a strong bond, the presence of lone pairs causes repulsion, making it less reactive than expected.

5. **Order of Reactivity**:
- Based on bond strengths, the order of reactivity in the halogenation of alkanes is:
- Iodine (I2) > Bromine (Br2) > Chlorine (Cl2) > Fluorine (F2)
- This means that iodine reacts the fastest, followed by bromine, then chlorine, and finally fluorine.

6. **Conclusion**:
- Therefore, the rate of reaction of alkanes with halogens in the halogenation process is highest with iodine and lowest with fluorine.

### Final Answer:
The order of reactivity of alkanes with halogens in the halogenation process is: **Iodine > Bromine > Chlorine > Fluorine**.

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