Question

An unknown colorless liquid has the formula \(\mathrm{C}_{3} \mathrm{H}_{8} \mathrm{O} .\) Draw the structures for the three compounds that have this formula.

Short answer

The three structures are 1-propanol, 2-propanol, and methyl ethyl ether.

Step-by-step solution

Identify the molecular formula

The given molecular formula is \(\text{C}_3\text{H}_8\text{O}\). This indicates the compound has three carbon atoms, eight hydrogen atoms, and one oxygen atom.

Draw the first structure (propanol)

The first possible structure is propanol, which is an alcohol. Place the hydroxyl group (\(\text{-OH}\)) on the end of a three-carbon chain. This forms 1-propanol: \(\text{CH}_3\text{CH}_2\text{CH}_2\text{OH}\).

Draw the second structure (another isomer of alcohol)

The second structure is to place the hydroxyl group on the second carbon of the chain. This results in 2-propanol: \(\text{CH}_3\text{CHOH}\text{CH}_3\).

Draw the third structure (an ether)

The third possible structure is where the oxygen is in between two carbon atoms, forming an ether, methyl ethyl ether: \(\text{CH}_3\text{O}\text{CH}_2\text{CH}_3\).

Key concepts

Molecular Formula

A molecular formula provides critical information about a chemical compound, indicating the exact number of each type of atom present in a molecule. For example, the molecular formula \(\text{C}_3\text{H}_8\text{O}\) specifies that any molecule represented by this formula contains exactly three carbon atoms, eight hydrogen atoms, and one oxygen atom.
However, a molecular formula doesn't provide information about how these atoms are arranged in space, leading to different structural possibilities called isomers.
Understanding the molecular formula is the first step in exploring various isomers, as it tells us the basic "ingredients" of any structure we might draw or imagine based on this formula. Knowing the amount of each atom type helps us systematically explore and validate the structural possibilities.

Propanol

Propanol is one of the alcohols that fits the molecular formula \(\text{C}_3\text{H}_8\text{O}\). Alcohols are characterized by the presence of a hydroxyl group (\(-OH\)) attached to a carbon atom.
In this case, propanol can exist in two main isomeric forms, 1-propanol and 2-propanol.
1-propanol has the hydroxyl group attached to the terminal carbon atom of the three-carbon chain, represented as \(\text{CH}_3\text{CH}_2\text{CH}_2\text{OH}\).
2-propanol, on the other hand, has the hydroxyl group on the second carbon of the chain, looking like \(\text{CH}_3\text{CHOH}\text{CH}_3\).
These structural differences impact properties such as boiling point and solubility in water, despite sharing the same molecular formula.

Ether

Ethers are another type of organic compound that can also match the molecular formula \(\text{C}_3\text{H}_8\text{O}\). Unlike alcohols, ethers feature an oxygen atom connected between two carbon chains, creating a different type of "link" in the structure.
In our specific case, the compound can be organized into an isomer known as methyl ethyl ether, represented by the structure \(\text{CH}_3\text{O}\text{CH}_2\text{CH}_3\).
Ethers have different physical and chemical properties compared to alcohols. Generally, they are less dense than alcohols and often more volatile.
Their lack of hydroxyl groups also means they do not form hydrogen bonds as alcohols do, affecting their solubility and reactivity.

Organic Chemistry

Organic chemistry is the branch of chemistry that focuses on compounds primarily made of carbon and hydrogen, often containing other elements like oxygen, nitrogen, and sulfur.
It's a vast field that includes studying the structure, composition, properties, reactions, and preparation of carbon-containing compounds.
Organic compounds are central to all living organisms and the study of organic chemistry is crucial in creating pharmaceuticals, plastics, fuels, and many other materials.
This field helps understand and create isomers with the same molecular formula, like propanol and ethers. Understanding these isomers' properties and behaviors is a key aspect of organic chemistry, providing insights that drive innovation and application in diverse industries.