Section 2.9 introduced the idea of structural isomerism, with 1-propanol and 2-propanol as examples. Determine which of these properties would distinguish these two substances: (a) boiling point, (b) combustion analysis results, (c) molecular weight, (d) density at a given temperature and pressure. You can check on the properties of these two compounds in Wolfram Alpha (http://www.wolframalpha.com/) or the CRC Handbook of Chemistry and Physics.

Verified step by step guidance

1. Identify the structural differences between 1-propanol and 2-propanol. 1-propanol has the hydroxyl group (-OH) attached to the first carbon, while 2-propanol has it attached to the second carbon.
2. Consider how the position of the hydroxyl group affects the boiling point. The different structures can lead to variations in intermolecular forces, such as hydrogen bonding, which influences boiling points.
3. Analyze the combustion analysis results. Both compounds have the same molecular formula (C3H8O), so their combustion products (CO2 and H2O) will be identical, making this property not useful for distinction.
4. Evaluate the molecular weight. Since both 1-propanol and 2-propanol have the same molecular formula, their molecular weights are identical, so this property cannot distinguish them.
5. Examine the density at a given temperature and pressure. The structural differences can lead to variations in how molecules pack together, potentially affecting the density, which could be used to distinguish between the two isomers.

Key Concepts

Structural Isomerism

Structural isomerism occurs when two or more compounds have the same molecular formula but different structural arrangements of atoms. In the case of 1-propanol and 2-propanol, they both share the formula C3H8O but differ in the position of the hydroxyl (-OH) group. This difference in structure leads to variations in their physical and chemical properties.

Boiling Point

The boiling point of a substance is the temperature at which its vapor pressure equals the external pressure, causing it to change from liquid to gas. For isomers like 1-propanol and 2-propanol, differences in molecular structure can lead to variations in intermolecular forces, such as hydrogen bonding, which significantly affect their boiling points.

Density

Density is defined as mass per unit volume and is an important physical property that can vary between isomers. The arrangement of atoms in a molecule influences its overall mass and volume, leading to differences in density. For 1-propanol and 2-propanol, their distinct structures result in measurable differences in density, which can be used to distinguish between the two substances.