Arrange the following in the order of their increasing reactivity in nucleophilic substitution reactions.
`CH_3F, CH_3 Cl, CH_3Br , CH_3I`

Explanation

To determine the order of increasing reactivity in nucleophilic substitution reactions for the haloalkanes \( CH_3F, CH_3Cl, CH_3Br, \) and \( CH_3I \), we need to consider the bond dissociation energies of the carbon-halogen bonds. The reactivity in nucleophilic substitution reactions is inversely related to the bond strength; that is, weaker bonds break more easily, leading to higher reactivity.

### Step-by-Step Solution:

1. **Identify the Haloalkanes**: We have four haloalkanes: \( CH_3F \) (methyl fluoride), \( CH_3Cl \) (methyl chloride), \( CH_3Br \) (methyl bromide), and \( CH_3I \) (methyl iodide).

2. **Understand Bond Dissociation Energy**: The bond dissociation energy (BDE) is the energy required to break a bond. In this case, we are interested in the C-X bond where X is the halogen. The lower the BDE, the easier it is for the bond to break, and hence, the more reactive the compound is in nucleophilic substitution reactions.

...