Naming Alkenes - Vanderbilt University

1 Naming AlkenesSuffix: -eneMany of the same rules for alkanes apply to the parent hydrocarbon by locating the longest carbon chain that contains thedouble bond and name it according to the number of carbons with the suffix -ene. H3 CCH2CH2 CCH2CH2H3CH3 CCH2CH2 CCH2CH2H3 CParent = pentenenot hexene (does not contain double bond) Number the carbons of the parent chain so the double bond carbons have thelowest possible numbers. H3 CCH2CH2 CHCHCH31234562-hexeneb. If the double bond is equidistant from each end, number so the first substituenthas the lowest number. out the full name, numbering the substituents according to their position in thechain and list them in alphabetical the double bond by the number of the first alkene carbon. more than one double bond is present, indicate their position by using the numberof the first carbon of each double bond and use the suffix -diene (for 2 doublebonds), -triene (for 3 double bonds), -tetraene (for 4 double bonds), etc.

2 H2 CCHCH2 CHCH2123451,4-pentadieneH2 CCHCHCHCH3123451, Cycloalkenes are named in a similar way. Number the cycloalkene so the doublebond carbons get numbers 1 and 2, and the first substituent is the lowest If there is a substituent on one of the double bond carbons, it gets number ,5-dimethylcyclopenteneNOT2,3-dimethylcy clopenteneAlkenes as Substituents:CHCH2ethenyl or vinyl(vinylcyclohexane)CH2 CHCH22-propenyl or allyl(allylcyclohexane)CH2methylene(meth ylenecyclohexane)HCCH3ethylidene(ethylid enecyclohexane)Non-IUPAC Alkenes (Table , pg. 184)H2 CCH2 CHCH2H3 Cethylene(ethene)propylene(propene)CCH2H 3CH3 Cisobutylene(2-methylpropene)CCHH2 CCH3CH2isoprene(2-methyl-1,3-butadiene)