Hydrocarbon compounds exist not only in the linear chain form, but also as rings. Chemical properties, functional groups, and reactions of ring compounds are very similar to those of the linear chain form. Both cycloalkanes and cycloalkene type compounds exist. Many important biological, vitamin, and drug compounds may have rings as part of their structures. The simplest compound that can be a ring form must contain three carbons. Cyclopropane, a sweet-smelling colorless gas, is sometimes used as an anesthetic. It produces a deep unconsciousness in a matter of seconds.

Cyclopentane is shown on the left. The general formula for rings is CnH2n. For cyclic alkanes, carbon must still have four bonds, hence each carbon is attached to two others and two hydrogens are groups may be attached to each carbon (structure on the right). A brief structure shows only the bonds as in the compound on the extreme left. The carbons with appropriate hydrogens are assumed at each angle change. You need to be able to recognize and draw both types of structures.

Properties
Structure	Physical Properties	Chemical Reactivity
Cyclic Alkanes CnH2n Two H's or other groups may be bonded to the carbon in an alkane ring. Cyclic Alkenes CnH2n-2(2n-2 for every double bond present)	Non polar- good industrial solvents for other nonpolar compounds Insoluble in water liquid at room temperature	Alkanes unreactive. Alkenes have approximately the same reactions as straight chain alkenes. All compounds: Combustion Reaction

The prefix "cyclo-" is used for alkane and alkene hydrocarbon ring compounds. The root and endings are the same. A brief structure shows only the bonds. The carbons with appropriate hydrogens are at each angle change.
Graphic	Name	Name explanation
Example on the left	1,2-dimethylcyclohexane	A 6 carbon ring = cyclohexane There are two methyl groups attached to cyclohexane it is necessary to number the positions. Arbitrarily one methyl group is defined as number 1. For this compound the second methyl groups is on the second carbon, hence 1,2. Use "di" to indicate two methyl groups = 1,2-dimethylcyclohexane
For the Quiz questions below, click on Quiz to get a graphic, then write the name of the structure, finally check the first answer pull down box for the correct name, and the second answer for an explanation of how it was named.
Quiz	Answer methylcyclo- pentane	Answer 5 carbon ring = cyclopentane 1 C methyl branch = methylcyclo- pentane
Quiz	Answer cyclohexane	Answer 6 carbon ring =cyclohexane
Quiz	Answer 1,4-dimethyl- cyclohexane	Answer 6 carbon ring = cyclohexane 2 methyl branches pick one for no. 1 count to 4th C for second methyl = 1,4-dimethyl- cyclohexane