Which is the correct increasing order of boiling points

Options

A. Butane`lt`1-chlorobutane`lt`1-bromobutane`lt`1-iodobutane
B. 1-iodobutane`lt`1-bromobutane`lt`1-chlorobutane`lt`Butane
C. Butane`lt`1-iodobutane`lt`1-bromobutane`lt`1-chlorobutane
D. Butane`lt`1-chlorobutane`lt`1-iodobutane`lt`1-bromobutane

Explanation

To determine the correct increasing order of boiling points for the compounds butane, 1-chlorobutane, 1-bromobutane, and 1-iodobutane, we need to consider the factors that influence boiling points, specifically molecular weight and intermolecular forces.

### Step-by-Step Solution:

1. **Identify the Compounds**:
- The compounds we are comparing are:
- Butane (C4H10)
- 1-Chlorobutane (C4H9Cl)
- 1-Bromobutane (C4H9Br)
- 1-Iodobutane (C4H9I)

2. **Consider Molecular Weights**:
- The molecular weights of the halogenated compounds increase with the size of the halogen:
- Chlorine (Cl) has a molecular weight of approximately 35.5 g/mol.
- Bromine (Br) has a molecular weight of approximately 80 g/mol.
- Iodine (I) has a molecular weight of approximately 127 g/mol.
- Therefore, the order based on molecular weight is:
- 1-Chlorobutane < 1-Bromobutane < 1-Iodobutane

3. **Analyze Boiling Points**:
- Generally, boiling points increase with increasing molecular weight due to stronger London dispersion forces and dipole-dipole interactions.
- Butane, being a non-polar molecule with the lowest molecular weight, will have the lowest boiling point.

4. **Rank the Compounds**:
- Based on the above analysis, we can rank the compounds in order of increasing boiling points:
- Butane (lowest boiling point)
- 1-Chlorobutane
- 1-Bromobutane
- 1-Iodobutane (highest boiling point)

5. **Final Order**:
- Therefore, the correct increasing order of boiling points is:
- Butane < 1-Chlorobutane < 1-Bromobutane < 1-Iodobutane

### Conclusion:
The correct increasing order of boiling points is:
**Butane < 1-Chlorobutane < 1-Bromobutane < 1-Iodobutane**