Which of the following statements are correct?

Options

A. Butan`-2-` one shows tautomerism.
B. Compounds containing asymmetric `C` atoms are always optically active.
C. Members belonging to the same class of compounds are called isomers.
D. Isomers have the same molecular formula.

Explanation

To determine which statements are correct, let's analyze each statement one by one.

### Step 1: Analyze the first statement
**Statement 1:** Butane-2-one shows tautomerism.

- **Explanation:** Tautomerism is a type of isomerism where two isomers (tautomers) are in dynamic equilibrium, typically involving the migration of a hydrogen atom. Butane-2-one (CH3C(=O)C2H5) can exist in equilibrium with its enol form (CH2=C(OH)C2H5). Therefore, this statement is **correct**.

### Step 2: Analyze the second statement
**Statement 2:** Compounds containing asymmetric carbon atoms are always optically active.

- **Explanation:** While compounds with asymmetric (chiral) carbon atoms can be optically active, they are not always so. For example, a compound can have multiple chiral centers and also possess a plane of symmetry, making it optically inactive (a meso compound). Thus, this statement is **incorrect**.

### Step 3: Analyze the third statement
**Statement 3:** Members belonging to the same class of compounds are called isomers.

- **Explanation:** Isomers are defined as compounds that have the same molecular formula but different structures. Members of the same class of compounds (e.g., alkanes, alcohols) are known as homologues, not isomers. Therefore, this statement is **incorrect**.

### Step 4: Analyze the fourth statement
**Statement 4:** Isomers have the same molecular formula.

- **Explanation:** This is the definition of isomers. Isomers are compounds that have the same molecular formula but differ in structure or arrangement. Therefore, this statement is **correct**.

### Conclusion
After analyzing all four statements, we find that:
- **Correct Statements:** 1 and 4
- **Incorrect Statements:** 2 and 3

### Final Answer
The correct statements are 1 and 4.

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