1. Cyclic and Aromatic Hydrocarbons SCH4U Spring 2012

2. Cyclic Hydrocarbons (Cyclo-) Hydrocarbon chains that form rings Have at least three carbon atoms Can be alkanes, alkenes and alkynes General formula for cyclic alkanes: C n H 2n

3. Naming cyclic hydrocarbons Identify the root o Preceded by “cyclo-” Identify the suffix o Not necessary to indicate the location of the double or triple bonds Identify the prefix o If there are no or only one side group on a cyclic alkane, the carbon atoms are not numbered o If there are two or more side groups on a cyclic alkane, numbering must give the lowest possible numbers to all side groups o If the molecule is a cyclic alkene or cyclic alkyne, the multiple bond takes highest priority Name the compound

4. Questions Name the following:

5. Questions Draw the following: o 4-ethyl-2-methylcyclopentene o methylcyclobutane o 2-ethyl-3-propylcyclohexane o 1, 2-dimethylcyclohexane

6. Aromatic hydrocarbons (-benzene) Derived from benzene ring (C 6 H 6 ) Aliphatic compounds: do not contain a benzene ring Benzene ring: o All six carbon-carbon bonds are identical in length o Length of the carbon-carbon bonds is intermediate between a single and a double bond o Resonance hybrid o Delocalized electrons: electrons that make up the second bond in the “double bonds” are equally shared by all six carbon atoms o Conjugated double bonds o Stable structures

7. Naming aromatic hydrocarbons Identify the root (-benzene) Identify the prefix o prioritize alkyl side groups with six or fewer carbon atoms in alphabetical order o Continue to number in the direction of the nearest side group Name the compound (prefix+root)

8. Naming aromatic hydrocarbons If a benzene ring is attached to a single hydrocarbon chain that has more than six carbon atoms, the benzene ring becomes a side group (-phenyl)

9. Questions Name each aromatic hydrocarbon:

10. Drawing aromatic hydrocarbons Draw the benzene ring If there is more than one side group, number the carbon atoms in the ring Add the side groups (have six or fewer carbon atoms)

11. Questions Draw the condensed structural formula for each aromatic hydrocarbon: o 1,3-diethyl-4-methyl-2-propylbenzene o 1-ethyl-3-propylbenzene Draw the line structural formula for: o 2-phenyl-5-propyloctane o 1,4-dimethylbenzene