The number of pentyl alcohols producing blue colouration in the Victor-Meyer's test is.

Explanation

To determine the number of pentyl alcohols that produce blue coloration in the Victor-Meyer test, we need to identify the secondary alcohols among the pentyl alcohols. The Victor-Meyer test distinguishes alcohols based on their degree of substitution:

1. **Understanding the Degrees of Alcohols**:
- Primary (1°) alcohols do not produce blue coloration.
- Secondary (2°) alcohols produce blue coloration.
- Tertiary (3°) alcohols produce colorless solutions.

2. **Identifying Pentyl Alcohols**:
- Pentyl alcohols are alcohols with a five-carbon chain (C5H11OH).
- The structural formula can be represented as CH3-CH2-CH2-CH2-CH2OH.

3. **Drawing Structural Isomers**:
- We can have different structural isomers of pentyl alcohols:
- **1-Pentanol** (Primary)
- **2-Pentanol** (Secondary)
- **3-Pentanol** (Secondary)
- **2-Methyl-1-butanol** (Primary)
- **3-Methyl-1-butanol** (Primary)
- **2-Methyl-2-butanol** (Tertiary)
- **3-Methyl-2-butanol** (Secondary)
- **2,2-Dimethyl-1-propanol** (Tertiary)

4. **Identifying Secondary Alcohols**:
- From the isomers listed, we need to identify which are secondary:
- **2-Pentanol** (2°)
- **3-Pentanol** (2°)
- **3-Methyl-2-butanol** (2°)

5. **Counting the Secondary Alcohols**:
- The secondary alcohols identified are:
- 2-Pentanol
- 3-Pentanol
- 3-Methyl-2-butanol
- Thus, there are **three** pentyl alcohols that will produce blue coloration in the Victor-Meyer test.

**Final Answer**: The number of pentyl alcohols producing blue coloration in the Victor-Meyer test is **3**.

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