Arrange the following compounds in the increasing order of boiling points :
`C_2H_5 OC_2 H_5 , C_4 H_9 COOH, C_4 H_9 OH`

Explanation

To arrange the compounds `C_2H_5OC_2H_5` (diethyl ether), `C_4H_9COOH` (butanoic acid), and `C_4H_9OH` (butanol) in increasing order of boiling points, we need to consider the types of intermolecular forces present in each compound.

### Step 1: Identify the compounds and their types
1. **Diethyl ether (C2H5OC2H5)**: This compound is an ether, which primarily exhibits weak van der Waals forces (London dispersion forces) and dipole-dipole interactions.
2. **Butanoic acid (C4H9COOH)**: This compound is a carboxylic acid, which can form strong hydrogen bonds due to the presence of the -COOH group.
3. **Butanol (C4H9OH)**: This compound is an alcohol, which can also form hydrogen bonds due to the presence of the -OH group, but generally has weaker hydrogen bonding compared to carboxylic acids.

### Step 2: Compare the boiling points based on intermolecular forces
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