`Ph- CH = CH - overset(O)overset(||) C - OH`
The IUPAC name is :

Options

A. 3-phenyl prop-2-enoic acid
B. 3-phenol prop-1-enoic acid
C. 3-carboxy-prop-1-ene benzene
D. but-2-enoic acid

Explanation

To determine the IUPAC name of the compound `Ph-CH=CH-C(=O)OH`, we will follow the systematic steps for naming organic compounds.

### Step-by-Step Solution:

1. **Identify the Longest Carbon Chain**:
- The longest carbon chain in the compound consists of three carbon atoms. This chain includes a double bond and a functional group (carboxylic acid).
- The structure can be represented as:
```
CH2=CH-C(=O)OH
```

2. **Number the Carbon Atoms**:
- Start numbering from the end closest to the functional group (the carboxylic acid group, -COOH). This gives priority to the functional group.
- Numbering:
- Carbon 1: C(=O)OH (carboxylic acid)
- Carbon 2: CH
- Carbon 3: CH2
- So, the numbering is:
```
1 2 3
COOH - CH = CH2
```

3. **Identify the Functional Group and Double Bond**:
- The functional group is a carboxylic acid (-COOH), which takes precedence in naming.
- There is a double bond between Carbon 2 and Carbon 3.

4. **Identify Substituents**:
- There is a phenyl group (Ph) attached to Carbon 3.
- Therefore, the substituent is located on Carbon 3.

5. **Construct the Name**:
- The base name for three carbon atoms is "propane".
- Since there is a double bond starting at Carbon 2, we use "prop-2-ene".
- The presence of the carboxylic acid group modifies the name to "prop-2-enoic acid".
- The phenyl substituent on Carbon 3 is indicated as "3-phenyl".
- Combining these, the full name becomes "3-phenylprop-2-enoic acid".

### Final IUPAC Name:
The IUPAC name of the compound `Ph-CH=CH-C(=O)OH` is **3-phenylprop-2-enoic acid**.

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