Consider the following substances
1. Propan -2-ol
2. Propanone
3. 2 - methyl propene
The correct sequence of increasing order of boiling point is

Options

A. `1 gt 2 gt 3`
B. `1 gt 3 gt 2`
C. `2 gt 1 gt 3`
D. `3 gt 2 gt 1`

Answer

To determine the correct sequence of increasing order of boiling points for the given substances: Propan-2-ol, Propanone, and 2-methylpropene, we can analyze the molecular structures and the factors that influence boiling points.

### Step-by-Step Solution:

1. **Identify the Structures**:
- **Propan-2-ol (C3H8O)**: This is an alcohol with the structure CH3-CHOH-CH3. It can form hydrogen bonds due to the presence of the hydroxyl (-OH) group.
- **Propanone (C3H6O)**: This is a ketone, commonly known as acetone, with the structure CH3-CO-CH3. It has a carbonyl group (C=O) which is polar but does not form hydrogen bonds like alcohols do.
- **2-methylpropene (C4H8)**: This is an alkene with the structure CH2=C(CH3)-CH3. It is a hydrocarbon and does not have any polar functional groups that can lead to significant intermolecular forces.

2. **Analyze the Intermolecular Forces**:
- **Propan-2-ol**: Exhibits strong hydrogen bonding due to the -OH group. Hydrogen bonds significantly increase boiling points.
- **Propanone**: Has a polar carbonyl group, which allows for dipole-dipole interactions, but lacks hydrogen bonding capabilities.
- **2-methylpropene**: Being a hydrocarbon, it primarily exhibits weak van der Waals forces (London dispersion forces), leading to a lower boiling point compared to the other two substances.

3. **Rank the Substances by Boiling Point**:
- **Propan-2-ol**: Highest boiling point due to hydrogen bonding.
- **Propanone**: Intermediate boiling point due to dipole-dipole interactions.
- **2-methylpropene**: Lowest boiling point due to weak van der Waals forces.

4. **Final Sequence**:
- The correct sequence of increasing order of boiling points is:
- 2-methylpropene < Propanone < Propan-2-ol

### Conclusion:
Thus, the correct sequence of increasing order of boiling points is:
**2-methylpropene < Propanone < Propan-2-ol**