Download NOMENCLATURE FOR ORGANIC CHEMISTRY

NOMENCLATURE FOR ORGANIC CHEMISTRY
Alkanes
1. Determine the longest continuous chain of carbons. The length of this chain determines the
base name (see names below).
2. Any branched groups are named as an alkyl group. The alkyl group uses the same base name,
but changes the ending to -yl (see names below). A few alkyls have special names**.
3. The complete name of the branched group(s) requires a number position corresponding to the
carbon on the longest continuous chain identified in #1. The lowest combination of numbers
is used when determining which end of the chain to begin the numbering.
4. When there are multiple branched groups of the same type, the Greek prefixes of di-, tri-,
tetra-, penta-, etc. are used in front of the alkyl name.
# of C
1
2
3
4
5
6
7
8
9
10
Formula
CH4
CH3CH3
CH3CH2CH3
CH3(CH2)2CH3
CH3(CH2)3CH3
CH3(CH2)4CH3
CH3(CH2)5CH3
CH3(CH2)6CH3
CH3(CH2)7CH3
CH3(CH2)8CH3
Name
Methane
Ethane
Propane
Butane
Pentane
Hexane
Heptane
Octane
Nonane
Decane
Alkyl formula
-CH3
-CH2CH3
-CH2CH2CH3
*
*
*
*
*
*
*
Alkyl name
Methyl
Ethyl
Propyl
*the alkyl names do continue in the same trend, but are rare and we will not worry about them.
**the (CH3)2CH- alkyl group is called isopropyl and the (CH3)3C- alkyl group is called t-butyl.
CH3
ex) CH3 CH2 CH2 CH CH CH3
CH3
CH3
ex) CH3 CH2 CH2 CH2 C CH3
CH3
name: 2,3-dimethyl hexane
name: 2,2-dimethyl hexane
CH3 CH3
ex) CH3 CH2 CH C CH3
CH2 CH2 CH3
name: ???
CH3
ex) CH3 CH CH2 CH CH CH3
CH3 CH2
CH2 CH3
name: ???
ex) What is the condensed structural formula for: 2,2,3-trimethylpentane;
3-ethyl-2,5-dimethyloctane
Functional Groups
When a functional group is present, the suffix of the base name is altered according to the correct
functional group present. A number in some cases is also needed to clarify any potential
structural isomers. The suffixes are:
Functional Group
-OH
-CHO
-RR'C=O
-COOH
-C=C-C≡C-
Suffix
-ol
-al
-one
-oic acid
-ene
-yne
Numbering Required?
more than 2 C's
no (always C#1)
more than 3 C's
no (always C#1)
more than 3 C's
more than 3 C's
Cycloalkanes
These are ring structures where the two ends of the chain connect together. The most common
ones are those with five and six carbon rings. Others are possible, but are not always as stable.
Pictured below are the geometric symbols used to represent cyclopropane, cyclobutane,
cyclopentane, and cyclohexane (respectively). As you can see, the name "cyclo" is placed in
front of the base alkane name. Mono-substituted cycloalkanes do not require numbers as all
positions on the ring are equivalent. Di-substituted cycloalkanes require numbers and may be
numbered clockwise or counter-clockwise. A cycloalkene always has the location of the double
bond in the C1-C2 position.
Benzene derivatives
These are molecules containing the benzene ring (C6H6) unit whose symbol is shown below. For
mono-substituted benzene's, many have common names. A methyl group produces the molecule
named Toluene, an -OH group produces the molecule named Phenol, and a -NH2 group produces
the molecule named Aniline. For di-substituted benzenes, number is required or (old system) use
of ortho, meta, and para substitution patterns are acceptable.