Which of the following is/are correct?

Options

A. Pentane & Neopentane are chain isomers.
B. Diethylamine & Sec-butylamine are functional isomers.
C. Methyl formate & Acetic acid are functional isomers.
D. Propanone & Propanal are functional isomers.

Explanation

To solve the question "Which of the following is/are correct?" regarding isomerism, we will analyze each statement provided in the context of isomer types: chain isomers and functional isomers.

### Step-by-step Solution:

1. **Understanding Isomerism**:
- **Chain Isomers**: These are compounds that have the same molecular formula but differ in the arrangement of the carbon chain.
- **Functional Isomers**: These are compounds that have the same molecular formula but differ in the functional groups.

2. **Analyzing the Statements**:
- **Statement 1**: Pentane and Neopentane are chain isomers.
- **Structure of Pentane (C5H12)**:
- CH3-CH2-CH2-CH2-CH3
- **Structure of Neopentane (C5H12)**:
- (CH3)4C
- Both have the same molecular formula (C5H12) but differ in the arrangement of the carbon chain. Thus, this statement is **correct**.

- **Statement 2**: Diethyl amine and secondary butyl amine are functional isomers.
- **Structure of Diethyl amine**:
- (C2H5)2NH
- **Structure of Secondary Butyl amine**:
- CH3-CH(NH2)-CH2-CH3
- Both have the same molecular formula (C4H11N) but differ in the functional groups (amine vs. secondary amine). Thus, this statement is **correct**.

- **Statement 3**: Methyl formate and acetic acid are functional isomers.
- **Structure of Methyl Formate**:
- HCOOCH3
- **Structure of Acetic Acid**:
- CH3COOH
- Both have the same molecular formula (C2H4O2) but differ in functional groups (ester vs. carboxylic acid). Thus, this statement is **correct**.

- **Statement 4**: Propanone and propanol are functional isomers.
- **Structure of Propanone**:
- CH3COCH3
- **Structure of Propanol**:
- CH3CH2CHO
- Both have the same molecular formula (C3H6O) but differ in functional groups (ketone vs. aldehyde). Thus, this statement is **correct**.

3. **Conclusion**:
- All statements (1, 2, 3, and 4) are correct. Therefore, the answer is that all options are correct.

### Final Answer:
All statements are correct.

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