Arrange the following compounds in the increasing order of their boiling points.
`CH_3CH_2CH_2CHO`
`CH_3CH_2CH_2CH_2OH`
`H_5C_2-O-C_2H_5`
`CH_3CH_2CH_2CH_2CH_3`

Options

A. `IV lt I lt II lt III`
B. `IV lt III lt II lt I`
C. `IV lt III lt I lt II`
D. `IV lt II lt III lt I`

Answer

To arrange the compounds in increasing order of their boiling points, we need to consider the factors that affect boiling points, primarily molecular weight and the presence of hydrogen bonding.

### Step 1: Identify the compounds and their structures
1. **CH₃CH₂CH₂CHO** (Butanal - an aldehyde)
2. **CH₃CH₂CH₂CH₂OH** (Butanol - an alcohol)
3. **H₅C₂-O-C₂H₅** (Diethyl ether - an ether)
4. **CH₃CH₂CH₂CH₂CH₃** (Pentane - an alkane)

### Step 2: Analyze the compounds for boiling point factors
- **Butanal (CH₃CH₂CH₂CHO)**: This compound can engage in some hydrogen bonding due to the presence of the carbonyl group (C=O).
- **Butanol (CH₃CH₂CH₂CH₂OH)**: This compound can form strong hydrogen bonds due to the hydroxyl group (–OH), which typically leads to a higher boiling point.
- **Diethyl ether (H₅C₂-O-C₂H₅)**: Ethers can engage in hydrogen bonding, but not as extensively as alcohols. Therefore, its boiling point will be lower than that of butanol but higher than that of hydrocarbons.
- **Pentane (CH₃CH₂CH₂CH₂CH₃)**: This is a non-polar hydrocarbon and does not engage in hydrogen bonding, leading to the lowest boiling point among the given compounds.

### Step 3: Compare the boiling points
1. **Pentane (C₅H₁₂)**: Lowest boiling point due to lack of hydrogen bonding.
2. **Diethyl ether (C₄H₁₀O)**: Higher boiling point than pentane because of the presence of oxygen, allowing for some hydrogen bonding.
3. **Butanal (C₄H₈O)**: Higher boiling point than diethyl ether due to the presence of the carbonyl group, which allows for some hydrogen bonding.
4. **Butanol (C₄H₁₀O)**: Highest boiling point due to strong hydrogen bonding from the hydroxyl group.

### Final Order of Boiling Points
Based on the analysis:
- **Pentane < Diethyl ether < Butanal < Butanol**

### Answer
The increasing order of boiling points is:
**CH₃CH₂CH₂CH₂CH₃ (Pentane) < H₅C₂-O-C₂H₅ (Diethyl ether) < CH₃CH₂CH₂CHO (Butanal) < CH₃CH₂CH₂CH₂OH (Butanol)**