Question

There are three compounds that have the molecular formula \(\mathrm{C}_{3} \mathrm{H}_{8} \mathrm{O}\). Draw the structure for each isomer and classify the hydrocarbon derivative.

Short answer

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

Step-by-step solution

Understand the Molecular Formula

The molecular formula \( \mathrm{C}_3\mathrm{H}_8\mathrm{O} \) suggests it could be either an alcohol or an ether. Alcohols contain an \(-\mathrm{OH}\) group and ethers contain an \(\mathrm{O}\) atom between carbon atoms.

Draw the Alcohol Isomers

One possible alcohol isomer can be drawn by attaching the \(-\mathrm{OH}\) group to the end of a 3-carbon chain: \(\mathrm{CH}_3\mathrm{CH}_2\mathrm{CH}_2\mathrm{OH}\), which is known as 1-propanol. Another isomer is formed by placing the \(-\mathrm{OH}\) on the middle carbon: \(\mathrm{CH}_3\mathrm{CH}(\mathrm{OH})\mathrm{CH}_3\), known as 2-propanol.

Draw the Ether Isomer

For the ether isomer, the \(\mathrm{O}\) atom can be placed between two of the carbons. This forms \(\mathrm{CH}_3\mathrm{O}\mathrm{CH}_2\mathrm{CH}_3\), known as methyl ethyl ether or methoxyethane.

Classify the Compounds

The first two structures are alcohols, specifically primary alcohol (1-propanol) and secondary alcohol (2-propanol). The third structure is an ether (methyl ethyl ether).

Key concepts

Molecular Formula

A molecular formula is a concise way of expressing information about the atoms in a molecule. It tells you which elements are present and how many atoms of each element are part of the compound. For example, the molecular formula \( \mathrm{C}_3\mathrm{H}_8\mathrm{O} \) indicates a molecule consisting of three carbon (C) atoms, eight hydrogen (H) atoms, and one oxygen (O) atom.

This formula can be used to describe molecules like alcohols or ethers. However, it does not give any detail about how these atoms are connected. That’s where structural formulas come into play, revealing the actual arrangement of the atoms within the molecule.

Structural Isomers

Structural isomers are molecules with the same molecular formula but different arrangements of atoms. This difference in structure can result in very different chemical properties and functions, even though the composition is the same.

For molecules with the formula \( \mathrm{C}_3\mathrm{H}_8\mathrm{O} \) , the possible isomers include:

• 1-Propanol: A primary alcohol with the \(-\mathrm{OH}\) group at the end of the carbon chain.
• 2-Propanol: A secondary alcohol with the \(-\mathrm{OH}\) group attached to the middle carbon.
• Methyl ethyl ether: An ether with an \(\mathrm{O}\) atom placed between two carbon atoms.

Identifying and understanding these isomers is crucial in chemistry as they dictate how the molecule behaves in reactions.

Alcohols

Alcohols are a class of compounds characterized by the presence of one or more hydroxyl \((\mathrm{-OH})\) groups. They have the general formula \(\mathrm{R-OH}\), where \(\mathrm{R}\) represents an alkyl group.

Alcohols can be classified based on the carbon atom to which the hydroxyl group is attached:

• Primary alcohols: The \(-\mathrm{OH}\) group is attached to a carbon atom connected to only one other carbon atom (e.g., 1-propanol).
• Secondary alcohols: The \(-\mathrm{OH}\) group is attached to a carbon atom connected to two other carbon atoms (e.g., 2-propanol).

The features of alcohols make them versatile for use in solvents, fuels, and manufacturing, attributable to the polarity of their \(\mathrm{-OH}\) groups.

Ethers

Ethers are compounds that feature an oxygen atom bonded to two alkyl or aryl groups, represented by the general formula \(\mathrm{R-O-R'}\). This creates a symmetrical or asymmetrical molecule depending on whether the two groups are the same or different.

For example, methyl ethyl ether (methoxyethane), \(\mathrm{CH}_3\mathrm{O}\mathrm{CH}_2\mathrm{CH}_3\), is an ether with \(\mathrm{O}\) positioned between a methyl group and an ethyl group. Its structure is key in determining its boiling point, solubility, and reactivity.

• Solvent properties: Ethers generally have low reactivity, making them suitable as solvents.
• Volatility: They are usually volatile and have distinctive odors.

Understanding ethers helps in identifying their role and uses in chemical synthesis and industrial applications.