Cyclic and Aromatic Hydrocarbons SCH4U Spring 2012

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: CnH2n

Naming cyclic hydrocarbons

• Identify the rooto Preceded by “cyclo-”

• Identify the suffixo Not necessary to indicate the location of the double or triple bonds

• Identify the prefixo If there are no or only one side group on a cyclic alkane, the carbon

atoms are not numberedo If there are two or more side groups on a cyclic alkane, numbering

must give the lowest possible numbers to all side groupso If the molecule is a cyclic alkene or cyclic alkyne, the multiple bond

takes highest priority

• Name the compound

Questions

•Name the following:

Questions

•Draw the following:

o4-ethyl-2-methylcyclopenteneomethylcyclobutaneo2-ethyl-3-propylcyclohexaneo1, 2-dimethylcyclohexane

Aromatic hydrocarbons (-benzene)• Derived from benzene ring (C6H6)• Aliphatic compounds: do not contain a benzene ring• Benzene ring:oAll six carbon-carbon bonds are identical in length o Length of the carbon-carbon bonds is intermediate

between a single and a double bondoResonance hybridoDelocalized electrons: electrons that make up the

second bond in the “double bonds” are equally shared by all six carbon atoms

oConjugated double bondso Stable structures

Naming aromatic hydrocarbons

•Identify the root (-benzene)•Identify the prefixoprioritize alkyl side groups with six or

fewer carbon atoms in alphabetical orderoContinue to number in the direction of the

nearest side group•Name the compound (prefix+root)

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)

Questions

•Name each aromatic hydrocarbon:

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)

Questions

•Draw the condensed structural formula for each aromatic hydrocarbon:

o1,3-diethyl-4-methyl-2-propylbenzeneo1-ethyl-3-propylbenzene

•Draw the line structural formula for:o2-phenyl-5-propyloctaneo1,4-dimethylbenzene