How to Count Carbon Atoms in Organic Chemistry
Organic chemistry is the science of molecules that are built around carbon atoms: natural gas, petroleum, plastics, alcohols and many other industrial chemicals. This branch of science has its own specialized vocabulary, including a method for naming molecules according to how many carbon atoms they contain. Learning the words organic chemists use to count carbon atoms is the first step to understanding how organic compounds are named.
Instructions
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Learn the prefixes that represent the numbers 1 to 10. One is "meth," two is "eth," three is "prop" (pronounced "prope"), four is "but-" (pronounced "byute"), five is "pent," six is "hex," seven is "hept," eight is "oct," nine is "non" (pronounced "known") and ten is "dec" (pronounced "deck").
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Use a mnemonic technique if you have trouble remembering the prefixes. For example, you might want to substitute the prefixes for the numbers in the song "One Little, Two Little, Three Little Indians," and sing: "Meth little, eth little, prop little carbons; but little, pent little, hex little carbons; hept little, oct little, non little carbons; dec little carbon atoms."
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Learn the suffixes that describe organic molecules that have single, double or triple bonds between the carbon atoms. Single bond molecules end in "-ane," double bond molecules end in "-ene" and triple bond molecules end in "-yne."
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Combine the 10 prefixes with the 3 suffixes to form names of 30 different organic molecules. For example, "octane" would be a molecule with eight carbons atoms and only single bonds between them; "butene" would be a molecule with four carbon atoms and at least one double bond; "propyne" would be a molecule with three carbons and at least one triple bond.
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Learn prefixes for numbers higher than 10. Eleven is "undec," 12 is "dodec," 13 is "tridec," 14 is "tetradec," 15 is "pentadec," 16 is "hexadec," 17 is "heptadec," 18 is "octadec," 19 is "nonadec," and 20 is "eicos."
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Tips & Warnings
This article is not intended to be a complete guide to naming organic molecules. There are more rules than just counting carbons and looking at the bonds. If you would like to know more, refer to the Resources section.
