Write down structure of the following compounds:
3-methylbutanoic acid

Explanation

To write down the structure of 3-methylbutanoic acid, we will follow these steps:

### Step 1: Identify the Base Structure
- The name "butanoic acid" indicates that the main chain has 4 carbon atoms (but-). The suffix "-oic acid" indicates the presence of a carboxylic acid group (-COOH) at one end of the carbon chain.

**Hint:** The prefix "but-" corresponds to a four-carbon chain.

### Step 2: Draw the Carbon Chain
...