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

Options

A. But-2-ene-1, 4-dicarboxylic acid
B. But-2-ene-1, 4-dioic acid
C. Ethene dicarboxylic acid
D. Ethene dioic acid

Explanation

To determine the IUPAC name of the compound `HOOC - CH = CH - COOH`, we will follow a systematic approach:

### Step-by-Step Solution:

1. **Identify the Longest Carbon Chain**:
- The compound contains a total of four carbon atoms in a chain. The longest continuous chain that includes the functional groups (carboxylic acids) is `HOOC - CH = CH - COOH`.
- Therefore, the parent chain consists of 4 carbon atoms.

2. **Determine the Root Name**:
- The root name for a four-carbon alkane is "butane". Since we have functional groups, we will modify this name accordingly.

3. **Number the Carbon Atoms**:
- We need to number the carbon atoms in such a way that the functional groups receive the lowest possible numbers.
- Starting from one end, we can number the carbon chain as follows:
- Carbon 1: COOH (carboxylic acid)
- Carbon 2: CH (double bond)
- Carbon 3: CH (double bond)
- Carbon 4: COOH (carboxylic acid)

4. **Identify the Functional Groups**:
- There are two carboxylic acid groups (COOH) at carbon 1 and carbon 4.
- There is a double bond between carbon 2 and carbon 3.

5. **Construct the Name**:
- Since there are two carboxylic acid groups, we use the prefix "di-" to indicate their presence.
- The position of the carboxylic acid groups is at carbon 1 and carbon 4, which we denote as "1,4".
- The presence of the double bond at carbon 2 modifies the name from "butane" to "butene".
- Therefore, the complete name becomes "but-2-ene" for the double bond, and we add the suffix for the carboxylic acids.

6. **Final IUPAC Name**:
- Combining all the information, the final IUPAC name of the compound is **but-2,4-dienoic acid**.