Arrange the following alkyl halides in order of dehydrohalgenation, `C_2H_5I` , C_2H_5Cl` , C_2H_5Br` , C_2H_5F`

Options

A. `C_2H_5FgtC_2H_5ClgtC_2H_5BrgtC_2H_5I`
B. `C_2H_5IgtC_2H_5BrgtC_2H_5ClgtC_2H_5F`
C. `C_2H_5IgtC_2H_5ClgtC_2H_5BrgtC_2H_5F`
D. `C_2H_5FgtC_2H_5IgtC_2H_5BrgtC_2H_5Cl`

Answer

To arrange the alkyl halides \( C_2H_5I \), \( C_2H_5Br \), \( C_2H_5Cl \), and \( C_2H_5F \) in order of their dehydrohalogenation power, we need to consider the ability of the halogen atoms to leave the molecule during the reaction. The process of dehydrohalogenation involves the removal of a hydrogen atom and a halogen atom from the alkyl halide.

### Step-by-Step Solution:

1. **Understanding Dehydrohalogenation**:
- Dehydrohalogenation refers to the elimination reaction where a hydrogen atom and a halogen atom are removed from an alkyl halide.
- The ease of this reaction depends on the stability of the resulting alkene and the leaving ability of the halogen.

2. **Identify the Halogens**:
- The halogens in the given compounds are iodine (I), bromine (Br), chlorine (Cl), and fluorine (F).

3. **Evaluate the Leaving Group Ability**:
- The ability of a halogen to act as a leaving group increases as we move down the group in the periodic table. This is due to the increasing atomic size and decreasing electronegativity.
- The order of leaving group ability is: \( I^- > Br^- > Cl^- > F^- \).

4. **Apply the Order to the Given Alkyl Halides**:
- For the alkyl halides:
- \( C_2H_5I \): Iodine is the leaving group.
- \( C_2H_5Br \): Bromine is the leaving group.
- \( C_2H_5Cl \): Chlorine is the leaving group.
- \( C_2H_5F \): Fluorine is the leaving group.
- Based on the leaving group ability, we can predict the order of dehydrohalogenation.

5. **Arrange the Alkyl Halides**:
- The alkyl halides can be arranged in the following order based on their dehydrohalogenation power:
- \( C_2H_5I \) (most reactive)
- \( C_2H_5Br \)
- \( C_2H_5Cl \)
- \( C_2H_5F \) (least reactive)

### Final Order:
The final order of dehydrohalogenation for the given alkyl halides is:
\[ C_2H_5I > C_2H_5Br > C_2H_5Cl > C_2H_5F \]