Which of the following molecules would you expect to be optically active ?
`(i) C Cl_2 `
`(ii) CHCl Br F `
(iii) 2-methylbutane
`(iv) CH_3CH_2 COOH `
(v) Butan-2-ol
(vi) 2-hydroxypropanoic acid.

Explanation

To determine which of the provided molecules are optically active, we need to identify if they contain a chiral center. A chiral center is typically a carbon atom that is bonded to four different groups or atoms, resulting in non-superimposable mirror images.

### Step-by-Step Solution:

1. **(i) CCl₂ (Dichlorocarbene)**:
- The carbon in CCl₂ is bonded to two chlorine atoms and does not have four different substituents.
- **Conclusion**: Not optically active.

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