Question

\(\mathrm{CH}_{3} \mathrm{COOH}\) is the given IUPAC name of ethanoic acid.

Short answer

Answer: The molecular formula of ethanoic acid is \(\mathrm{C}_{2}\mathrm{H}_{4}\mathrm{O}_{2}\). The structural formula is: ``` H H O | | || H-C-C=O | | H O-H ```

Step-by-step solution

Determine the chemical formula

For ethanoic acid, the IUPAC name \(\mathrm{CH}_{3} \mathrm{COOH}\) tells us the molecular composition: - 2 carbon atoms - 4 hydrogen atoms - 2 oxygen atoms So the molecular formula for ethanoic acid is \(\mathrm{C}_{2}\mathrm{H}_{4}\mathrm{O}_{2}\).

Understand the functional group

Ethanoic acid is a carboxylic acid, which means it has a -COOH group attached to the carbon chain. The -COOH group is composed of a carbonyl group (C=O) and a hydroxyl group (O-H).

Draw the structural formula

To draw the structural formula, start with the two-carbon chain and add the functional group: 1. Draw a straight chain of two carbon (C) atoms. 2. Since ethanoic acid has a carboxylic acid functional group, attach the -COOH group to the end carbon atom of the chain. 3. The remaining carbon atom needs to have a total of four bonds. It already has one bond to the other carbon atom and the carbonyl group, so we need to add three hydrogen (H) atoms to satisfy its valency. The structural formula for ethanoic acid is: ``` H H O | | || H-C-C=O | | H O-H ``` In summary, ethanoic acid has a molecular formula of \(\mathrm{C}_{2}\mathrm{H}_{4}\mathrm{O}_{2}\) and the structural formula shown above.

Key concepts

IUPAC nomenclature

The IUPAC nomenclature system is a standardized method of naming chemical compounds. This system helps chemists worldwide to communicate unambiguously about chemical substances. For many organic acids, such as ethanoic acid, the IUPAC naming relies on identifying the longest chain containing the functional group and naming it accordingly.
The name "ethanoic acid" indicates a molecule with two carbon atoms (since "eth-" implies two carbons) and the presence of a carboxylic acid group (-COOH). The suffix "-oic acid" is used to denote it as a carboxylic acid. This systematic approach ensures that each compound only has one official name, aiding in effective communication and understanding.

molecular formula determination

Determining the molecular formula involves calculating the exact number and type of atoms in a molecule. For ethanoic acid, the molecular formula \( \mathrm{C}_{2}\mathrm{H}_{4}\mathrm{O}_{2} \) is derived from its structural composition. Ethanoic acid contains:

• 2 carbon atoms,
• 4 hydrogen atoms,
• 2 oxygen atoms.

By considering the IUPAC name (ethanoic acid), you can deduce the number of carbons from the "eth-" prefix and correctly attribute hydrogen and oxygen to the carboxylic acid group. This systematic approach aids in identifying the true molecular identity of the compound, crucial for balancing chemical reactions and understanding chemical properties.

carboxylic acid functional group

The carboxylic acid functional group, represented as -COOH, is essential for characterizing organic acids like ethanoic acid. This functional group is composed of two smaller groups:

• The carbonyl group (C=O), which contains a carbon atom double-bonded to an oxygen atom.
• The hydroxyl group (O-H), which consists of an oxygen atom single-bonded to a hydrogen atom.

These two groups together form the carboxylic acid group, defining the molecule's acidic properties. The presence of the carboxylic group gives the molecule its name and certain chemical properties, like its ability to donate a proton (H⁺) in reactions, classifying it as an acid.

structural formula drawing

Drawing the structural formula of a compound like ethanoic acid visually represents its molecular geometry. To begin, illustrate the basic skeleton of the molecule, which for ethanoic acid involves a chain of two carbon atoms. Then, incorporate the functional group:
1. Start by drawing two carbon atoms linearly connected. 2. At the terminal end, attach the carboxylic acid group (-COOH). This involves bonding one of the carbon atoms to a carbonyl group (C=O) and a hydroxyl group (O-H). 3. Ensure that each carbon atom meets the four bonds rule:

• The first carbon bonds to three hydrogens.
• The second carbon bonds to one carbonyl bond and the OH group.

This structural formula helps in visualizing bond interactions and is essential for performing molecular analysis, like calculating molecular mass or predicting reactivity.