Among the following the one that gives positive iodoform test upon reaction with ` I _ 2 and NaOH ` is \

Options

A. ` CH_ 3 CH_2 CH (OH ) CH _ 2 CH _ 3 `
B. `CH_3 - CH (CH _ 3) CH _2 - OH `
C. `C_6 H _ 5 - CH_ 2 - CH _ 2 OH `
D. `PhCH (OH ) CH _ 3 `

Explanation

To determine which compound gives a positive iodoform test upon reaction with I2 and NaOH, we need to identify the presence of a methyl ketone or a specific type of alcohol that can yield a methyl ketone upon oxidation. Here’s a step-by-step solution:

### Step 1: Understand the Iodoform Test
The iodoform test is used to identify methyl ketones or certain alcohols. The general reaction involves the reaction of a carbonyl compound (specifically a methyl ketone or ethanol) with iodine (I2) in the presence of sodium hydroxide (NaOH), resulting in the formation of iodoform (CHI3), which is a yellow precipitate.

### Step 2: Identify the Requirements for a Positive Test
1. **Methyl Ketones**: Compounds of the form CH3C(=O)R, where R can be any alkyl group.
2. **Ethanol**: The only primary alcohol that gives a positive iodoform test.
3. **Specific Secondary Alcohols**: Alcohols that can be oxidized to form a methyl ketone.

### Step 3: Analyze Each Option
Now, let's analyze the provided options:

1. **Option A**: CH3CH2CHOHCH2CH3 (2-degree alcohol)
- This is a secondary alcohol but does not have the required structure to give a positive iodoform test. **Negative test**.

2. **Option B**: CH3CH(OH)CH3 (1-degree alcohol)
- This is a primary alcohol. Only ethanol gives a positive test among primary alcohols. **Negative test**.

3. **Option C**: C6H5CH2CH2OH (1-degree alcohol)
- This is also a primary alcohol and does not meet the criteria for a positive test. **Negative test**.

4. **Option D**: C6H5CHOHCH3 (2-degree alcohol)
- This compound can be oxidized to form a methyl ketone (specifically, it has the structure CH3C(=O)R). Thus, it can give a positive iodoform test. **Positive test**.

### Conclusion
The compound that gives a positive iodoform test is **Option D**: C6H5CHOHCH3.

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