The optically inactive compound from the following is :-

Options

A. 2-chloropropanal
B. 2-chlorobutane
C. 2-chloro-2-methylbutane
D. 2-chloropentane

Answer

To determine the optically inactive compound from the given options, we need to identify which compound has a chiral carbon and which does not. A chiral carbon is a carbon atom that is bonded to four different groups. If a compound has at least one chiral carbon, it is considered optically active. Conversely, if a compound has no chiral carbons or has a carbon bonded to groups that are not all different, it is optically inactive.

Let’s analyze each option step by step:

### Step 1: Analyze 2-Chloropropanol
- **Structure**: CH3-CHOH-Cl
- The carbon atom attached to the hydroxyl group (OH) is bonded to:
- CH3 (methyl group)
- OH (hydroxyl group)
- Cl (chlorine)
- H (hydrogen)
- Since all four groups attached to this carbon are different, this carbon is chiral.
- **Conclusion**: 2-Chloropropanol is optically active.

### Step 2: Analyze 2-Chlorobutane
- **Structure**: CH3-CH(Cl)-CH2-CH3
- The carbon atom attached to the chlorine is bonded to:
- CH3 (methyl group)
- Cl (chlorine)
- CH2 (methylene group)
- CH2 (methylene group)
- This carbon is also bonded to four different groups, making it chiral.
- **Conclusion**: 2-Chlorobutane is optically active.

### Step 3: Analyze 2-Chloro-2-methylbutane
- **Structure**: CH3-C(Cl)(CH3)-CH2-CH3
- The carbon atom attached to the chlorine is bonded to:
- CH3 (methyl group)
- Cl (chlorine)
- CH3 (methyl group)
- CH2 (methylene group)
- Here, two of the groups are the same (two CH3 groups), which means this carbon is not chiral.
- **Conclusion**: 2-Chloro-2-methylbutane is optically inactive.

### Step 4: Analyze 2-Chloropentane
- **Structure**: CH3-CH(Cl)-CH2-CH2-CH3
- The carbon atom attached to the chlorine is bonded to:
- CH3 (methyl group)
- Cl (chlorine)
- CH2 (methylene group)
- CH2 (methylene group)
- This carbon is also bonded to four different groups, making it chiral.
- **Conclusion**: 2-Chloropentane is optically active.

### Final Answer
The optically inactive compound from the options provided is **2-Chloro-2-methylbutane**.

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