Which of the following is not characteristic of alcohols?

Options

A. They are lighter than water .
B. Their boiling points rise fairly uniformly with rising molecular weight .
C. Lower members are insoluble in water and organic solvents but the solubility regularly increases with molecular mass .
D. Lower members have a pleasant smell and burning taste , higher members are colourless and tasteless .

Answer

To solve the question "Which of the following is not characteristic of alcohols?", we will analyze each statement provided in the options and determine their validity regarding alcohols.

### Step-by-Step Solution:

1. **Analyze the First Statement: "They are lighter than water."**
- Alcohols generally have lower densities than water. This is due to the nature of hydrogen bonding in water, which is stronger than in alcohols. Therefore, this statement is **correct**.

2. **Analyze the Second Statement: "Their boiling point rises fairly uniformly with rising molecular weight."**
- As the molecular weight of alcohols increases, the boiling point also tends to increase due to stronger intermolecular forces, particularly hydrogen bonding. Thus, this statement is also **correct**.

3. **Analyze the Third Statement: "Lower members are insoluble in water and organic solvent, but solubility regularly increases with molecular mass."**
- This statement is **incorrect**. Lower molecular weight alcohols (like methanol and ethanol) are actually soluble in water due to their ability to form hydrogen bonds. As the molecular mass increases, the hydrophobic character of the alcohol increases, leading to decreased solubility in water. Therefore, this statement does not accurately describe alcohols.

4. **Analyze the Fourth Statement: "Lower members have pleasant smell and burning taste; higher members are colorless and tasteless."**
- Lower alcohols typically have a pleasant smell and can have a burning taste, while higher alcohols are generally colorless and tasteless. This statement is **correct**.

### Conclusion:
Based on the analysis, the statement that is **not characteristic of alcohols** is the third one: "Lower members are insoluble in water and organic solvent, but solubility regularly increases with molecular mass."

Thus, the answer is **Option C**.

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