The alcohol having least solubility in water is

Options

A. Ethanol
B. 1-Propanol
C. 1-Butanol
D. 1-Pentanol

Answer

To determine which alcohol has the least solubility in water, we need to consider the structure of alcohols and how they interact with water. Here’s a step-by-step solution:

### Step 1: Understand Alcohol Structure
Alcohols are organic compounds that contain one or more hydroxyl (-OH) groups attached to a carbon atom. The general formula for alcohols can be represented as R-OH, where R is an alkyl group.

### Step 2: Identify Factors Affecting Solubility
The solubility of alcohols in water primarily depends on:
- The ability to form hydrogen bonds with water.
- The length of the carbon chain (alkyl group) attached to the hydroxyl group.

### Step 3: Analyze Hydrogen Bonding
Shorter carbon chains (like methanol, ethanol) can form strong hydrogen bonds with water molecules due to their smaller size and the presence of the -OH group. As the carbon chain length increases, the hydrophobic (water-repelling) character of the alkyl group increases, which reduces the ability to form hydrogen bonds with water.

### Step 4: Compare Different Alcohols
Let’s consider some common alcohols:
- Methanol (CH3OH) - 1 carbon
- Ethanol (C2H5OH) - 2 carbons
- Propanol (C3H7OH) - 3 carbons
- Butanol (C4H9OH) - 4 carbons
- Pentanol (C5H11OH) - 5 carbons

### Step 5: Determine Solubility Trend
As the number of carbon atoms increases, the solubility in water decreases. This is because longer carbon chains lead to a greater hydrophobic effect, which interferes with the ability to form hydrogen bonds with water.

### Step 6: Identify the Alcohol with Least Solubility
Among the alcohols listed, pentanol (C5H11OH) has the longest carbon chain and therefore the least solubility in water.

### Conclusion
The alcohol having the least solubility in water is **pentanol (C5H11OH)**.

---