How many enols (including stereo isomers) exist for 3 - hexanone?

Options

A. Two
B. Three
C. Four
D. Six

Answer

To determine how many enols (including stereoisomers) exist for 3-hexanone, we can follow these steps:

### Step 1: Identify the Structure of 3-Hexanone
3-Hexanone is a ketone with the following structure:

\[ \text{CH}_3\text{CH}_2\text{C(=O)}\text{CH}_2\text{CH}_3 \]

This indicates that the carbonyl group (C=O) is located on the third carbon of a six-carbon chain.

### Step 2: Determine Possible Enol Forms
Enolization involves the conversion of the carbonyl group to an alkene with a hydroxyl group. For 3-hexanone, the enolization can occur at two different positions:

1. **Enol from the second carbon (C2)**:
- The enol structure will be:
\[ \text{CH}_3\text{C(OH)=CH}\text{CH}_2\text{CH}_3 \]

2. **Enol from the fourth carbon (C4)**:
- The enol structure will be:
\[ \text{CH}_3\text{CH}_2\text{C(OH)=CH}_2\text{CH}_3 \]

### Step 3: Identify Stereoisomers
Next, we need to determine if these enols can exhibit stereoisomerism:

1. **For the enol from C2**:
- This enol can exist in two forms based on the arrangement of groups around the double bond:
- **Z-form** (cis): where the hydroxyl (OH) and the methyl (CH3) groups are on the same side.
- **E-form** (trans): where the hydroxyl (OH) and the methyl (CH3) groups are on opposite sides.

2. **For the enol from C4**:
- Similarly, this enol can also exist in two forms:
- **Z-form** (cis): where the hydroxyl (OH) and the ethyl (C2H5) groups are on the same side.
- **E-form** (trans): where the hydroxyl (OH) and the ethyl (C2H5) groups are on opposite sides.

### Step 4: Count Total Enols Including Stereoisomers
From the above analysis:
- Enol from C2 has 2 stereoisomers (Z and E).
- Enol from C4 also has 2 stereoisomers (Z and E).

Thus, the total number of enols (including stereoisomers) for 3-hexanone is:

\[ 2 \text{ (from C2)} + 2 \text{ (from C4)} = 4 \text{ enols} \]

### Final Answer
Therefore, the total number of enols (including stereoisomers) that exist for 3-hexanone is **4**.

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