Question

The two isomers having the formula \(\mathrm{C}_{2} \mathrm{H}_{6} \mathrm{O}\) boil at \(-23^{\circ} \mathrm{C}\) and \(78.5^{\circ} \mathrm{C}\). Draw the structure of the isomer that boils at \(-23^{\circ} \mathrm{C}\) and of the isomer that boils at \(78.5^{\circ} \mathrm{C}\).

Short answer

The structure of the isomer that boils at -23°C is dimethyl ether (\(\ce{CH3-O-CH3}\)), and the structure of the isomer that boils at 78.5°C is ethanol (\(\ce{CH3-CH2-OH}\)).

Step-by-step solution

Determine possible isomers

First, we need to determine all possible isomers with the molecular formula \(\mathrm{C}_{2} \mathrm{H}_{6} \mathrm{O}\). In this case, there are two possible structures: ethanol and dimethyl ether.

Analyze the isomers' boiling points

Next, we need to analyze which isomer would correspond to which boiling point. Boiling points are affected by factors such as molecular weight and the strength of intermolecular forces. - Ethanol: (\(\mathrm{CH}_{3}\mathrm{CH}_{2}\mathrm{OH}\)) has a hydroxyl (-OH) group, which forms strong hydrogen bonds with other ethanol molecules, leading to a higher boiling point. - Dimethyl ether: (\(\mathrm{CH}_{3}\mathrm{OCH}_{3}\)) has an oxygen atom bonded to two methyl groups and does not form hydrogen bonds as effectively as ethanol, leading to a lower boiling point.

Match the isomers with the boiling points

Based on our analysis in Step 2, we can conclude that: - The isomer that boils at -23°C is dimethyl ether because it has weaker intermolecular forces (less hydrogen bonding) than ethanol. - The isomer that boils at 78.5°C is ethanol because it has stronger intermolecular forces (more hydrogen bonding) than dimethyl ether.

Draw the structures

Lastly, we will draw the structures of the isomers: - The structure of dimethyl ether (boiling at -23°C): \(\ce{CH3-O-CH3}\) - The structure of ethanol (boiling at 78.5°C): \(\ce{CH3-CH2-OH}\)