Question

Draw the condensed structural formulas of two esters and a carboxylic acid that each have molecular formula \(\mathrm{C}_{3} \mathrm{H}_{6} \mathrm{O}_{2}\).

Short answer

Propanoic acid: CH₃CH₂COOH; Methyl acetate: CH₃COOCH₃; Ethyl formate: CH₃CH₂COOCH₃.

Step-by-step solution

Understand the Molecular Formula

The molecular formula \(\text{C}_3 \text{H}_6 \text{O}_2\) indicates that each molecule will contain three carbon atoms, six hydrogen atoms, and two oxygen atoms. This formula can represent different isomers.

Identify Possible Carboxylic Acid Structure

A carboxylic acid contains a carbonyl group (C=O) and a hydroxyl group (OH) attached to the same carbon atom. For \(\text{C}_3 \text{H}_6 \text{O}_2\), one possible carboxylic acid is propanoic acid with the condensed structural formula \(\text{CH}_3 \text{CH}_2 \text{COOH}\).

Identify Possible Ester Structures

Esters are derived from carboxylic acids and alcohols. Common structures for esters include a carbonyl group (C=O) and an alkoxy group (O-R) attached to the carbonyl carbon. For \(\text{C}_3 \text{H}_6 \text{O}_2\), we can derive two esters: \(\text{CH}_3 \text{COOCH}_3\) (methyl acetate) and \(\text{CH}_3 \text{CH}_2 \text{COOCH}_3\) (ethyl formate).

Draw Condensed Structural Formulas

Represent the molecules using their condensed structural formulas: 1. Propanoic acid: \(\text{CH}_3 \text{CH}_2 \text{COOH}\) 2. Methyl acetate: \(\text{CH}_3 \text{COOCH}_3\) 3. Ethyl formate: \(\text{CH}_3 \text{CH}_2 \text{COOCH}_3\)

Key concepts

Molecular Formula

A molecular formula tells you the type and number of atoms in a molecule. For instance, the molecular formula \(\text{C}_3 \text{H}_6 \text{O}_2\) suggests that every molecule of the substance consists of three carbon atoms, six hydrogen atoms, and two oxygen atoms. This formula doesn't tell you how the atoms are connected, but it's very helpful as a starting point for identifying different possible structures, or 'isomers'. Understanding molecular formulas is crucial in organic chemistry because it sets the stage for deriving structures, like those of carboxylic acids and esters. Often, the challenge is to figure out how these atoms arrange themselves to create unique compounds.

Carboxylic Acid

Carboxylic acids are organic compounds characterized by a special group called the carboxyl group (COOH). This group consists of a carbon atom double-bonded to an oxygen atom and single-bonded to a hydroxyl group (OH). With the molecular formula \(\text{C}_3 \text{H}_6 \text{O}_2\), one possible carboxylic acid is propanoic acid. Its condensed structural formula is \(\text{CH}_3 \text{CH}_2 \text{COOH}\). This structure includes:

• A methyl group (\text{CH}_3)
• A methylene group (\text{CH}_2)
• A carboxyl group (\text{COOH})

Carboxylic acids are known for their acidity and are commonly found in nature and various industrial applications.

Esters

Esters are organic compounds derived from carboxylic acids and alcohols. They typically have a sweet smell and are often used in fragrances and flavorings. Esters contain a carbonyl group (C=O) and an alkoxy group (O-R) attached to the same carbon. For the molecular formula \(\text{C}_3 \text{H}_6 \text{O}_2\), we can consider two esters: methyl acetate (\text{CH}_3 \text{COOCH}_3) and ethyl formate (\text{CH}_3 \text{CH}_2 \text{COOCH}_3). Methyl acetate is formed when acetic acid reacts with methanol, while ethyl formate comes from the reaction between formic acid and ethanol. These reactions are typical condensation reactions, where water is eliminated in the process.

Isomers

Isomers are molecules with the same molecular formula but different structural arrangements. This concept is key in organic chemistry because different structures can result in very different chemical properties. For \(\text{C}_3 \text{H}_6 \text{O}_2\), we can have several isomers, including:

• Propanoic acid (a carboxylic acid)
• Methyl acetate (an ester)
• Ethyl formate (another ester)

Though these compounds have the same atoms in the same proportions, the way these atoms are connected changes the compound's characteristics entirely. Learning about isomers helps in understanding the diversity and complexity of organic molecules.

Organic Chemistry

Organic chemistry is the study of carbon-containing compounds. This field encompasses a vast range of substances, from simple molecules like methane to very complex structures like proteins and DNA. Organic chemistry involves understanding how these compounds are structured, how they interact, and how they can be synthesized. Core concepts in organic chemistry include:

• Functional groups (like carboxyl groups in carboxylic acids and ester groups in esters)
• Isomerism (different ways to arrange the same set of atoms)
• Molecular formulas (defining the types and quantities of atoms in a molecule)

Mastering these basics helps in making sense of more complex reactions and compounds in future learning.