The International Union of Pure and Applied Chemistry (IUPAC) has established rules to systematize the naming
of hydrocarbon molecules. A brief summary of those rules is presented here.
- Straight-chain hydrocarbon molecules that contain only singly-bonded carbons are called alkanes. When naming these molecules, the final syllable in their name is "ane."
- Straight-chain hydrocarbon molecules that contain at least one doubly-bonded carbon are called alkenes. When naming these molecules, the final syllable in their name is "ene."
- Straight-chain hydrocarbon molecules that contain at least one triply-bonded carbon are called alkynes. When naming these molecules, the final syllable in their name is "yne."
- Prefixes are attached to the last syllable to indicate the number of carbons in the hydrocarbon chain.
The IUPAC prefixes for the first twelve carbon chain lengths are:
|1 ||2 ||3 ||4 ||5 ||6
|meth ||eth ||prop ||but||pent||hex
|7 ||8 ||9 ||10 ||11 ||12
|hept ||oct ||non ||dec||undec||dodec
- Alkenes and alkynes with hydrocarbon chain lengths of four or greater require a numbering scheme
to the chain to designate the location of the multiple bond. The rules regarding this numbering scheme are:
a. The numbering system begins at the end of the molecule nearest the location of the multiple bond.
b. The number in the name is assigned relative to the carbon in the chain where the multiple bond begins.
c. A number is included for each multiple bond in the chain. The numbers are separated by commas.
d. A dash connects the number locations to the hydrocarbon name.
e. Prefixes are added to the "ene" or "yne" final syllable when more than 1 multiple bond is present. The first few prefixes
for these are:
|2 ||3 ||4 ||5 ||6 ||7 ||8
|di ||tri ||tetr ||pent||hex||hept||oct
- For ring hydrocarbons (excluding aromatics such as benzene), attach "cyclo" as the first syllable.
Copyright © 2010 Southeastern Louisiana University
ALL RIGHTS RESERVED.
Unofficial and external sites are not endorsed by Southeastern Louisiana University.