Structure of the compound whose `IUPAC` name is `3-`ethyl`-2-`hydroxy`-4-`methylhex`-3-`en`-5-`ynoic acid is

Options

A.
B.
C.
D.

Explanation

To determine the structure of the compound with the IUPAC name 3-ethyl-2-hydroxy-4-methylhex-3-en-5-ynoic acid, we will follow these steps:

### Step 1: Identify the main chain
The name indicates that the longest carbon chain is "hex," which means it consists of six carbon atoms.

### Step 2: Number the carbon chain
We will number the carbon chain from the end nearest to the carboxylic acid (–COOH) group, which is always given the lowest possible number.

- **Carbons:** 1 (COOH), 2, 3, 4, 5, 6

### Step 3: Identify and place the functional groups
- **2-hydroxy**: This indicates a hydroxyl (–OH) group is attached to the second carbon.
- **3-ethyl**: An ethyl group (–CH2CH3) is attached to the third carbon.
- **4-methyl**: A methyl group (–CH3) is attached to the fourth carbon.
- **hex-3-en**: Indicates a double bond between the third and fourth carbons.
- **5-ynoic acid**: Indicates a triple bond between the fifth and sixth carbons.

### Step 4: Draw the structure
1. Start with the six carbon chain.
2. Add the carboxylic acid group (–COOH) at carbon 1.
3. Add the hydroxyl group (–OH) at carbon 2.
4. Add the ethyl group (–CH2CH3) at carbon 3.
5. Add the methyl group (–CH3) at carbon 4.
6. Add a double bond between carbon 3 and carbon 4.
7. Add a triple bond between carbon 5 and carbon 6.

### Final Structure:
The structure can be drawn as follows:

```
CH3
|
CH3-CH-CH=CH-C≡C-COOH
| |
OH CH2
```

### Conclusion:
The correct structure for the compound with the IUPAC name 3-ethyl-2-hydroxy-4-methylhex-3-en-5-ynoic acid corresponds to option D.

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