Which reagent will you use for the following reaction ?
`CH_(3)CH_(2)CH_(2)CH_(3)toCH_(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 n-butane (CH₃CH₂CH₂CH₃) to form 1-chlorobutane (CH₃CH₂CH₂CH₂Cl) and 2-chlorobutane (CH₃CH₂CHClCH₃), we can follow these steps:

### Step 1: Identify the Reaction Type
The reaction involves the substitution of hydrogen atoms in n-butane with chlorine atoms. This is known as a substitution reaction, specifically a halogenation reaction where halogens replace hydrogen atoms in an organic compound.

**Hint:** Look for the type of reaction occurring; in this case, it’s a substitution reaction.

### Step 2: Recognize the Reactants and Products
The reactant is n-butane (C₄H₁₀), and the products are 1-chlorobutane and 2-chlorobutane. The reaction indicates that chlorine (Cl) is being introduced into the n-butane molecule.

**Hint:** Identify the starting material and the desired products to understand what changes are happening.

### Step 3: Determine the Reagent Required
For the chlorination of alkanes, chlorine gas (Cl₂) is typically used as the halogenating agent. However, this reaction requires specific conditions to proceed, particularly the presence of light.

**Hint:** Consider what reagent is commonly used for halogenation reactions and what conditions are necessary for the reaction to occur.

### Step 4: Specify the Reaction Conditions
Chlorination does not occur at room temperature without light. Therefore, ultraviolet (UV) light is necessary to initiate the reaction by breaking the Cl-Cl bond and generating reactive chlorine radicals.

**Hint:** Remember that some reactions require light or heat to proceed; in this case, UV light is essential for the chlorination process.

### Step 5: Write the Final Reaction
The complete reaction can be summarized as:
\[ \text{C}_4\text{H}_{10} + \text{Cl}_2 \xrightarrow{\text{UV light}} \text{C}_4\text{H}_9\text{Cl} + \text{C}_4\text{H}_9\text{Cl} \]
Where the products are 1-chlorobutane and 2-chlorobutane.

**Hint:** Ensure you understand how to represent the overall reaction and the role of each reagent.

### Conclusion
The appropriate reagent for the reaction is chlorine gas (Cl₂) in the presence of UV light.

**Final Answer:** Cl₂ in the presence of UV light.