Which reagent will you use for the following reaction?
`CH_3 CH_2 CH_2 CH_3 to CH_3 CH_2 CH_2 CH_2 Cl + CH_3 CH_2 CHClCH_3`

Options

A. Cl_2`/UV light
B. `NaCl + H_2 SO_4`
C. `Cl_2` gas in dark
D. `Cl_2` gas in the presence of iron in dark

Explanation

To determine the reagent needed for the reaction of butane to produce two different chlorinated products, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Reactant**:
The reactant is butane, which has the molecular formula \( C_4H_{10} \) and can be represented as \( CH_3CH_2CH_2CH_3 \).

2. **Understand the Reaction Type**:
The reaction involves the halogenation of butane, specifically chlorination, where hydrogen atoms in butane are replaced by chlorine atoms.

3. **Determine the Reagents**:
The typical reagent for halogenation is chlorine gas (\( Cl_2 \)). However, for the reaction to proceed, we need a condition that allows for the substitution of hydrogen atoms with chlorine.

4. **Identify the Reaction Conditions**:
The reaction requires a free radical initiator or UV light (\( h\nu \)) to initiate the reaction. This is because the chlorination of alkanes proceeds via a free radical mechanism.

5. **Mechanism of the Reaction**:
- **Initiation**: The \( Cl_2 \) molecule is dissociated into two chlorine free radicals (\( Cl \cdot \)) under UV light.
- **Propagation**: The chlorine free radicals then abstract hydrogen atoms from butane, forming chlorinated products and new chlorine radicals that continue the chain reaction.
- The products formed will be \( CH_3CH_2CH_2CH_2Cl \) (1-chlorobutane) and \( CH_3CH_2CHClCH_3 \) (2-chlorobutane).

6. **Final Answer**:
The reagent used for this reaction is \( Cl_2 \) in the presence of UV light (\( h\nu \)).