Which of the following has neither secondary nor tertiary hydrogen?

Options

A. Isobutane
B. Isopentane
C. Pentane
D. Neopentane

Answer

To determine which of the given compounds has neither secondary nor tertiary hydrogen, we need to analyze the structures of each compound and identify the types of hydrogen atoms present.

### Step-by-Step Solution:

1. **Understanding Secondary and Tertiary Hydrogens**:
- **Primary Hydrogen**: Attached to a primary carbon (a carbon bonded to one other carbon).
- **Secondary Hydrogen**: Attached to a secondary carbon (a carbon bonded to two other carbons).
- **Tertiary Hydrogen**: Attached to a tertiary carbon (a carbon bonded to three other carbons).

2. **Analyzing Each Compound**:
- **Option A: Isobutane (C4H10)**:
- Structure: CH3-CH(CH3)-CH3
- Carbon Analysis:
- 2 primary carbons (CH3 groups)
- 1 tertiary carbon (the central carbon)
- Contains tertiary hydrogen (from the tertiary carbon).

- **Option B: Isopentane (C5H12)**:
- Structure: CH3-CH(CH3)-CH2-CH3
- Carbon Analysis:
- 3 primary carbons (two CH3 groups and one CH2 group)
- 1 secondary carbon (the carbon attached to two other carbons)
- Contains secondary hydrogen (from the secondary carbon) and tertiary hydrogen (from the tertiary carbon).

- **Option C: Pentane (C5H12)**:
- Structure: CH3-CH2-CH2-CH2-CH3
- Carbon Analysis:
- 2 primary carbons (the two terminal CH3 groups)
- 3 secondary carbons (the CH2 groups in between)
- Contains secondary hydrogen (from the secondary carbons).

- **Option D: Neopentane (C5H12)**:
- Structure: (CH3)4C
- Carbon Analysis:
- 4 primary carbons (all CH3 groups)
- 1 quaternary carbon (the central carbon attached to four CH3 groups)
- Contains no secondary or tertiary hydrogens.

3. **Conclusion**:
- After analyzing all options, we find that **neopentane** (Option D) has neither secondary nor tertiary hydrogen.

### Final Answer:
The compound that has neither secondary nor tertiary hydrogen is **Option D: Neopentane**.