what is structure for `but-2-enoic` acid ?

Answer

To determine the structure of but-2-enoic acid, we can follow these steps:

### Step 1: Identify the carbon chain
The prefix "but-" indicates that the compound has a four-carbon chain. Therefore, we will have a chain of four carbon atoms.

### Step 2: Determine the type of bond
The suffix "-enoic" indicates that there is a double bond in the carbon chain. The "2" in "but-2-enoic" specifies that the double bond is located between the second and third carbon atoms.

### Step 3: Add the carboxylic acid group
The "-oic acid" part of the name indicates that this compound is a carboxylic acid. This means we need to add a carboxyl group (-COOH) to the end of the carbon chain.

### Step 4: Construct the structure
Now, we can construct the structure step by step:
- Start with the four carbon atoms in a chain: C1 - C2 - C3 - C4.
- Place a double bond between C2 and C3.
- Attach the carboxylic acid group (-COOH) to the first carbon (C1).

The final structure can be represented as follows:

```
H O
| ||
H--C--C==C--C--OH
| |
H H
```

This structure represents but-2-enoic acid, where:
- C1 has the carboxylic acid group (-COOH).
- C2 and C3 are connected by a double bond.
- C4 is the last carbon in the chain.

### Summary
The structure of but-2-enoic acid consists of a four-carbon chain with a double bond between the second and third carbons and a carboxylic acid group attached to the first carbon.

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