Which of the following is least soluble in water ?

Options

A. `CH_(3)OH`
B. `CH_(3) CH_(2)OH`
C. `CH_(3)CH_(2)CH_(2)OH`
D. `CH_(3)CH_(2)CH_(2)CH_(2)OH`

Answer

To determine which of the following alcohols is least soluble in water, we will analyze the solubility of each compound based on their structure and the number of carbon atoms they contain. The compounds we are considering are:

1. Methanol (CH₃OH)
2. Ethanol (C₂H₅OH)
3. Propanol (C₃H₇OH)
4. Butanol (C₄H₉OH)

### Step-by-Step Solution:

**Step 1: Identify the Structures of the Alcohols**
- Methanol: CH₃OH (1 carbon)
- Ethanol: C₂H₅OH (2 carbons)
- Propanol: C₃H₇OH (3 carbons)
- Butanol: C₄H₉OH (4 carbons)

**Step 2: Understand the Concept of Solubility in Water**
Alcohols are generally soluble in water due to their ability to form hydrogen bonds with water molecules. However, as the number of carbon atoms (alkyl groups) increases, the hydrophobic (water-repelling) character of the molecule also increases, which can reduce solubility.

**Step 3: Analyze Each Alcohol's Solubility**
- Methanol, with only one carbon atom, is highly soluble in water due to its small size and ability to form hydrogen bonds.
- Ethanol, with two carbon atoms, is also quite soluble, though slightly less than methanol.
- Propanol has three carbon atoms and is less soluble than ethanol but still has some solubility.
- Butanol, with four carbon atoms, is the largest of the four and has the most significant hydrophobic character, making it the least soluble in water.

**Step 4: Conclusion**
Based on the analysis, butanol (C₄H₉OH) is the least soluble in water compared to methanol, ethanol, and propanol due to its higher number of carbon atoms, which increases its hydrophobic interactions and decreases its ability to form hydrogen bonds with water.

### Final Answer:
**Butanol (C₄H₉OH) is the least soluble in water.**

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