Rank the following subtances in order of increasing boiling points (lowest`rarr`highest) :
I. `CH_(3)CH_(2)CH_(2)OH` II. `(CH_(3))_(2)CHOCH_(3)`
III. `(CH_(3))_(3)COH" " IV. (CH_(3))_(4)C.`

Options

A. `IltIIIltIIltIV`
B. `IIltIVltIIIltI`
C. `IVltIIltIIIltI`
D. `IIltIIIltIltIV`

Explanation

To rank the given substances in order of increasing boiling points, we need to consider the types of compounds and their structures. The substances provided are:

I. `CH₃CH₂CH₂OH` (1-Propanol)
II. `(CH₃)₂CHOCH₃` (2-Methoxypropane)
III. `(CH₃)₃COH` (2-Methyl-2-propanol)
IV. `(CH₃)₄C` (2-Methylpropane)

### Step-by-Step Solution:

1. **Identify the Types of Compounds**:
- **I. 1-Propanol**: This is a primary alcohol.
- **II. 2-Methoxypropane**: This is an ether.
- **III. 2-Methyl-2-propanol**: This is a tertiary alcohol.
- **IV. 2-Methylpropane**: This is an alkane.

2. **Understand the Boiling Point Trends**:
- Alcohols generally have higher boiling points than ethers due to the presence of hydrogen bonding in alcohols.
- Among alcohols, primary alcohols have higher boiling points than tertiary alcohols because primary alcohols can form more hydrogen bonds compared to tertiary alcohols.
- Ethers have lower boiling points than alcohols but are generally higher than alkanes due to their polar nature.
- Alkanes have the lowest boiling points among these types of compounds.

3. **Rank the Compounds**:
- **Lowest Boiling Point**: IV. 2-Methylpropane (alkane)
- **Next**: II. 2-Methoxypropane (ether)
- **Next**: III. 2-Methyl-2-propanol (tertiary alcohol)
- **Highest Boiling Point**: I. 1-Propanol (primary alcohol)

4. **Final Ranking**:
- IV < II < III < I
- Thus, the order of increasing boiling points is:
- 2-Methylpropane (IV) < 2-Methoxypropane (II) < 2-Methyl-2-propanol (III) < 1-Propanol (I)

### Final Answer:
**IV < II < III < I**