The correct order of boiling points of alkyl halides is

Options

A. `CH_3FgtCH_3ClgtCH_3BrgtCH_3I`
B. `CH_3FgtCH_3BrgtCH_3ClgtCH_3I`
C. `CH_3IgtCH_3BrgtCH_3ClgtCH_3F`
D. `CH_3ClgtCH_3BrgtCH_3FgtCH_3I`

Answer

To determine the correct order of boiling points of alkyl halides, we need to consider the molecular masses of the halogens attached to the alkyl group and the resulting Van der Waals forces.

### Step-by-Step Solution:

1. **Identify the Alkyl Halides**:
Alkyl halides are compounds where an alkyl group is bonded to a halogen (F, Cl, Br, I). For example, we can consider the following alkyl halides:
- Methyl fluoride (CH3F)
- Methyl chloride (CH3Cl)
- Methyl bromide (CH3Br)
- Methyl iodide (CH3I)

2. **Understand the Role of Molecular Mass**:
The boiling point of a substance is influenced by the strength of intermolecular forces. In the case of alkyl halides, the primary intermolecular force is the Van der Waals force, which increases with molecular mass. Therefore, the greater the molecular mass of the alkyl halide, the higher the boiling point.

3. **Compare the Molecular Masses of Halogens**:
We need to compare the molecular masses of the halogens:
- Fluorine (F) = 19 g/mol
- Chlorine (Cl) = 35.5 g/mol
- Bromine (Br) = 80 g/mol
- Iodine (I) = 127 g/mol

From this, we can see that the order of molecular mass from lowest to highest is:
- F < Cl < Br < I

4. **Determine the Boiling Point Order**:
Since the boiling point increases with increasing molecular mass, we can deduce the order of boiling points for the alkyl halides:
- Methyl fluoride (CH3F) will have the lowest boiling point.
- Methyl chloride (CH3Cl) will have a higher boiling point than CH3F.
- Methyl bromide (CH3Br) will have a higher boiling point than CH3Cl.
- Methyl iodide (CH3I) will have the highest boiling point.

5. **Final Order of Boiling Points**:
Therefore, the correct order of boiling points of the alkyl halides is:
**CH3F < CH3Cl < CH3Br < CH3I**