SolutionsPhysical Properties
1. Compare with the alkanes
Cyclohexane boils at 80.7 °C and melts at 6.6 °C; hexane boils at 69 °C and melts at −95 °C. Explain the differences.
The ring is more symmetric and rigid: cyclohexane molecules pack better in the solid (much higher melting point) and offer a larger, more constant contact surface in the liquid (somewhat higher boiling point).
2. Order by density
Arrange in order of increasing density: water, hexane and cyclohexane.
Hexane (≈0.66 g/mL) < cyclohexane (0.779 g/mL) < water (1.00 g/mL).
3. True or false?
- Cycloalkanes are soluble in water because they are cyclic.
- The physical constants of cycloalkanes are slightly higher than those of alkanes with the same number of carbons.
- Cyclopropane is a gas at room temperature.
- False. They are nonpolar, like alkanes, and do not dissolve in water.
- True.
- True. It boils at −32.7 °C.