The IUPAC name of `PhCH=CH-COOH` is

Options

A. 3-phenylprop-2-enoic acid
B. cinnamic acid
C. 1-carboxy-2-phenylethene
D. 1-phenylpropenoic acid

Explanation

To determine the IUPAC name of the compound `PhCH=CH-COOH`, we will follow the systematic approach for naming organic compounds. Here’s the step-by-step solution:

### Step 1: Identify the Parent Chain
The first step is to identify the longest continuous carbon chain that includes the functional group. In this case, the compound has a phenyl group (Ph) attached to a carbon chain that includes a double bond and a carboxylic acid group (COOH).

### Step 2: Number the Carbon Chain
We need to number the carbon chain starting from the end closest to the functional group (COOH). This gives priority to the carboxylic acid functional group.

- Starting from the carboxylic acid:
1. COOH (1)
2. CH (2)
3. CH (3)
4. Ph (4)

### Step 3: Determine the Parent Name
The parent chain consists of three carbon atoms (C3) with a double bond between the second and third carbon. The presence of the double bond indicates that we will use the suffix "-ene". Additionally, since there is a carboxylic acid, we will use the suffix "-oic acid".

- The base name for three carbons is "prop".
- Since the double bond is between the second and third carbon, we denote it as "prop-2-ene".
- The presence of the carboxylic acid modifies this to "prop-2-enoic acid".

### Step 4: Identify and Name the Substituent
The phenyl group (Ph) is a substituent on the third carbon of the chain. We will denote its position in the name.

- The substituent is at position 3, so we will include "3-phenyl" in the name.

### Step 5: Combine the Names
Now we combine the substituent and the parent name. The final IUPAC name will be:

**3-phenylprop-2-enoic acid**

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

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