What is the common name for ethanoic acid?

Analysis

The question asks for the common (trivial) name of ethanoic acid, which is a carboxylic acid with the chemical formula $CH_3COOH$.

Concept Explanation

In organic chemistry, compounds often have two types of names:

1. IUPAC Name: Based on a systematic set of rules (e.g., ethanoic acid). The prefix "eth-" indicates two carbon atoms, and the suffix "-oic acid" indicates a carboxylic acid group.
2. Common (Trivial) Name: Based on the historical source or origin of the compound. For carboxylic acids, these names are often derived from Latin or Greek words related to where the acid was first discovered.

Step-by-Step Solution

1. Identify the structure: Ethanoic acid has two carbon atoms ($CH_3COOH$).
2. Recall the origin: Ethanoic acid is the primary component of vinegar (aside from water). The Latin word for vinegar is acetum.
3. Match the common name: Because it is the acid found in vinegar, it is historically and commonly referred to as acetic acid.

Let's look at the other options to be sure:

• Butyric acid: This is the common name for butanoic acid (4 carbons). It is associated with the smell of rancid butter.
• Propionic acid: This is the common name for propanoic acid (3 carbons).
• Formic acid: This is the common name for methanoic acid (1 carbon). It is associated with ant stings (the Latin word for ant is formica).

Conclusion

The common name for ethanoic acid is acetic acid.

Exam Tip

To remember these quickly, associate the common names with their sources:

• Formic acid = Formica (Ants)
• Acetic acid = Acetum (Vinegar)
• Butyric acid = Butyrum (Butter)