The `IUPAC` name of `C_(6)H_(5)CH=CH-COOH` is `:`

Options

A. Succinic acid
B. 3-phenylprop-2-en-1-oic acid
C. Mandelic acid
D. Cinnamic acid

Answer

To determine the IUPAC name of the compound C₆H₅CH=CH-COOH, we will follow these steps:

### Step-by-Step Solution:

1. **Identify the Functional Groups**:
The compound has a carboxylic acid group (-COOH) and a double bond (alkene). The presence of the carboxylic acid takes priority in naming.

2. **Determine the Longest Carbon Chain**:
The longest carbon chain that includes the carboxylic acid is three carbons long (C1, C2, and C3). The structure can be visualized as:
- C1: COOH (carboxylic acid)
- C2: CH (double bond)
- C3: CH (connected to the phenyl group)

3. **Number the Carbon Chain**:
Start numbering from the carbon of the carboxylic acid (C1). The numbering will be:
- C1: COOH
- C2: CH (double bond)
- C3: CH (attached to the phenyl group)

4. **Identify Substituents**:
The phenyl group (C₆H₅) is attached to the third carbon (C3).

5. **Determine the Position of the Double Bond**:
The double bond is between C2 and C3. Since we start numbering from the carboxylic acid, the double bond is at position 2.

6. **Construct the Name**:
The base name for a three-carbon chain with a double bond is "propene". Since the double bond is at position 2, it is "prop-2-ene". The presence of the carboxylic acid changes the suffix to "-oic acid", and since it is at position 1, we denote it as "prop-2-enoic acid".

7. **Combine the Information**:
The full IUPAC name is "3-phenylprop-2-enoic acid".

### Final Answer:
The IUPAC name of C₆H₅CH=CH-COOH is **3-phenylprop-2-enoic acid**.