The compound which does not react with bromine easily at room temperature is

Options

A. phenol
B. 2-butyne
C. chlorobenzene
D. 1-pentene

Answer

To determine which compound does not react with bromine easily at room temperature, we will analyze each of the given compounds: phenol, butyl chloride, and pentane.

### Step-by-Step Solution:

1. **Identify the Compounds**: The compounds in question are:
- Phenol
- Butyl chloride (butyl bromide)
- Pentane
- Chlorobenzene

2. **Analyze Phenol**:
- Phenol contains a hydroxyl (-OH) group, which is an activating group for electrophilic aromatic substitution.
- When phenol reacts with bromine (Br2), it forms bromophenol. This reaction occurs readily at room temperature due to the activating nature of the -OH group.

3. **Analyze Butyl Chloride**:
- Butyl chloride is an alkyl halide.
- Alkyl halides can react with bromine to form addition products. This reaction can also occur at room temperature, although it may require some conditions to proceed efficiently.

4. **Analyze Pentane**:
- Pentane is a straight-chain alkane.
- Alkanes can react with bromine through a free radical substitution mechanism, but this reaction typically requires UV light or heat to initiate. At room temperature, the reaction is very slow.

5. **Analyze Chlorobenzene**:
- Chlorobenzene is an aromatic compound with a chlorine substituent.
- The presence of the chlorine atom makes chlorobenzene less reactive towards electrophilic substitution reactions compared to phenol.
- Chlorobenzene does not react with bromine at room temperature because the chlorine atom is a deactivating group for electrophilic substitution. Additionally, chlorine can oxidize bromine, preventing the formation of addition products.

6. **Conclusion**: Among the compounds analyzed, chlorobenzene is the one that does not react with bromine easily at room temperature.

### Final Answer:
The compound which does not react with bromine easily at room temperature is **Chlorobenzene**.