Which of the following statement is incorrect ?

Options

A. Diastereomers can be chiral.
B. Diastereomers can be achiral.
C. Enantiomers have similar physical and chemical properties always.
D. Presence of plane of symmetry confirms optical inactivity.

Answer

To determine which statement is incorrect among the given options, we will analyze each statement one by one.

### Step 1: Analyze the First Statement
**Statement:** Diastereomers can be chiral.

**Analysis:** This statement is true. Diastereomers are stereoisomers that are not mirror images of each other. Some diastereomers can indeed be chiral. For example, consider two diastereomers where one has a chiral center and the other does not.

### Step 2: Analyze the Second Statement
**Statement:** Diastereomers can be achiral.

**Analysis:** This statement is also true. Diastereomers can be achiral if they possess a plane of symmetry. For instance, if you have a compound with two chiral centers, it is possible for one diastereomer to be chiral while another is achiral.

### Step 3: Analyze the Third Statement
**Statement:** Enantiomers have similar physical and chemical properties always.

**Analysis:** This statement is incorrect. Enantiomers are non-superimposable mirror images of each other and generally have similar physical and chemical properties. However, they can behave differently in chiral environments (like biological systems) or when interacting with other chiral substances. For example, one enantiomer of a drug may be effective while the other is not.

### Step 4: Analyze the Fourth Statement
**Statement:** Presence of a plane of symmetry confirms optical inactivity.

**Analysis:** This statement is true. A compound that has a plane of symmetry is optically inactive because it cannot rotate plane-polarized light. Therefore, having a plane of symmetry confirms that the compound is optically inactive.

### Conclusion
After analyzing all the statements, we conclude that the incorrect statement is:

**Answer:** Enantiomers have similar physical and chemical properties always.

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