Organic Chemistry Hydrocarbon Nomenclature Prefixes

Organic Chemistry Hydrocarbon Nomenclature Prefixes The purpose of organic chemistry nomenclature is to indicate how many carbon atoms are in a chain, how the atoms are bonded together, and the identity and location of any functional groups in the molecule. The root names of hydrocarbon molecules are based on whether they form a chain or ring. A prefix to the name comes before the molecule. The prefix of the molecules name is based on the  number of carbon atoms. For example, a chain of six carbon atoms would be named using the prefix hex-. The suffix to the name is an ending that is applied that describes the types of chemical bonds in the molecule. An IUPAC name also includes the names of substituent groups (aside from hydrogen) that make up the molecular structure. Hydrocarbon Suffixes The suffix or ending of the name of a hydrocarbon depends on the nature of the chemical bonds between the carbon atoms. The suffix is -ane if all of the carbon-carbon bonds are single bonds (formula CnH2n2), -ene if at least one carbon-carbon bond is a double bond (formula CnH2n), and -yne if there is at least one carbon-carbon triple bond (formula CnH2n-2). There are other important organic suffixes: -ol means the molecule is alcohol or contains the -C-OH functional group-al means the molecule is an aldehyde or contains the OC-H functional group-amine means the molecule is an amine with the -C-NH2 functional group-ic acid indicates a carboxylic acid, which has the OC-OH functional group-ether indicates an ether, which has the -C-O-C- functional group-ate is an ester, which has the OC-O-C functional group-one is a ketone, which has the -CO functional group Hydrocarbon Prefixes This table lists the organic chemistry prefixes up to 20 carbons in a simple hydrocarbon chain. It would be a good idea to commit this table to memory early in your organic chemistry studies. Organic Chemistry Prefixes Prefix Number ofCarbon atoms Formula meth- 1 C eth- 2 C2 prop- 3 C3 but- 4 C4 pent- 5 C5 hex- 6 C6 hept- 7 C7 oct- 8 C8 non- 9 C9 dec- 10 C10 undec- 11 C11 dodec- 12 C12 tridec- 13 C13 tetradec- 14 C14 pentadec- 15 C15 hexadec- 16 C16 heptadec- 17 C17 octadec- 18 C18 nonadec- 19 C19 eicosan- 20 C20 Halogen substituents are also indicated using prefixes, such as fluoro (F-), chloro (Cl-), bromo (Br-), and iodo (I-).  Numbers are used to identify the position of the substituent. For example,  (CH3)2CHCH2CH2Br is named 1-bromo-3-methylbutane. Common Names Be aware, hydrocarbons found as rings (aromatic hydrocarbons) are named somewhat differently. For example, C6H6 is named benzene. Because it contains carbon-carbon double bonds, the -ene suffix is present. However, the prefix actually comes from the word gum benzoin, which as an aromatic resin used since the 15th century. When the hydrocarbons are substituents, there are several common names you may encounter: amyl: substituent with 5 carbonsvaleryl: substituent with 6 carbonslauryl: substituent with 12 carbonsmyristyl: substituent with 14 carbonscetyl or palmityl: substituent with 16 carbonsstearyl: substituent with 18 carbonsphenyl: common name for a hydrocarbon with benzene as a substituent