Write down structure of the following compounds:
2-methyl-2-butenoic acid

Explanation

To write down the structure of 2-methyl-2-butenoic acid, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Base Structure**:
- The name "butenoic acid" indicates that the base structure is a butenoic acid, which contains four carbon atoms (but-) and a carboxylic acid group (-COOH).

2. **Determine the Carbon Chain**:
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