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Cycloalkanes: Introduction, Structure and Physical Properties

Cycloalkanes: Physical Properties

Cyclopropane and cyclobutane are gases at room temperature while cyclopentane is already liquid at this temperature. Only van der Waals interactions play an important role in saturated hydrocarbons. Generally, alkanes are not very reactive. However, protonations, oxygenations, pyrolysis, radiolysis, and photolysis are possible under drastic conditions. Oxidation of alkanes can be carried out electrochemically. Lower cycloalkanes are especially flammable and form explosive mixtures with air (oxygen). Solubility in water is very low.

Because of symmetry and hindered rotation, the melting and boiling points of cycloalkanes are higher when compared to the corresponding n-alkanes. The alternating behavior of melting points of lower cycloalkanes with odd and even numbers of carbon atoms is even more pronounced here than in open-chain alkanes. The observed differences again can be attributed to the differences in the packing density of the crystalls of both series.

Physical properties of selected cycloalkanes
FormulaNameMp [ °C ]Bp [ °C ]Alkyl fragment
C3H6 Cyclopropane127.6-32.7Cyclopropyl-
C4H8 Cyclobutane-50.0-12.5Cyclobutyl-
C5H10 Cyclopentane-93.949.3Cyclopentyl-
C6H12 Cyclohexane6.680.7Cyclohexyl-
C7H14 Cycloheptane-12.0118.5Cycloheptyl-
C8H16 Cyclooctane14.3150.0Cyclooctyl-
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