Necessary Nomenclature Knowledge
The rules for naming molecules (IUPAC nomenclature) is complex, however, not every rule must be
understood in order to successfully name the relatively smaller molecules that commonly occur in 14C.
This guide provides a concise guide and summary to name those structures we worked so hard to assemble.
(There have been past exam questions asking names)
Main Idea
It is necessary to understand that names consist of 5 parts, assembled using this table
from right to left (i.e. functional group first,  stereoisomerism last)
Stereoisomerism
Substituents
Parent
Unsaturation
Functional group
1. Stereoisomerism
Indicates whether double bonds are cis/trans, E/Z, and
indicates stereocenters (R,S)
2. Substituents
Groups coming off the main chains
3. Parent
The main chain
4. Unsaturation
Identifies if there are any double or triple bonds
5. Functional group
The group after which the compound is named
Quick Steps to remember (Start at the end of the name, working backwards)
1.
2.
3.
4.
5.
Identify functional groups and order by hierarchy to determine suffix/prefix.
Look for number and location of double and triple bonds.
Identify the longest carbon chain as the parent chain.
Label each substituents that are attached to the parent chain.
Add Z/E (cis/trans) in the case of any present stereocenters or double bonds, (+/-)
cannot be determined without a laboratory experiment
Further explanation
Functional Groups
Functional groups are groups of atoms whose bonding is the same from molecule to molecule. These
specific arrangements of atoms have certain characteristics for reactivity, i.e. molecules with identical
functional groups have similar chemical and physical properties
•
•
•
If a compound has a functional group, add the indicated suffix to the name
If a compound has more than one functional group, use the suffix of the
functional group with greatest hierarchy and add the other functional group as a
prefix in the substituent part of the name
o Prefixed substituents are ordered alphabetically
o If there are multiples functional groups of the same type, either prefixed or
suffixed, the position numbers are ordered numerically
If there is no functional group, end the name with an “e”.
Priority
1
2
3
Functional Group
Cations
Carboxylic acids
Carboxylic acid derivativesEsters
Acyl halides
Amides
Imides
Amidines
Nitriles
Aldehydes
Ketones
Alcohols
Amines
Ethers
Peroxides
4
5
6
7
8
9
10
Formula
NH4+
-COOH
Prefix
-oniocarboxy-
Suffix
-onium
-oic acid
-COOR
-COX
-CONH2
-CON=C<
-C(=NH)NH2
-CN
-CHO
=O
-OH
-NH2
-O-OO-
R-oxycarbonyl
halocarbonylcarbamoyl-imidoamidinocyanoformyloxohydroxyamino-oxy-peroxy-
-R-oate
-oyl halide
-amide
-imide
-amidine
-nitrile
-al
-one
-ol
-amine
Unsaturation
Compounds with double or triple bonds are considered “unsaturated” because these compounds have less
hydrogens.
•
•
•
•
•
# of
Carbons
Prefix
•
•
The presence of a double or triple bonds is indicated with an “en” (double bond)
and “yne” (triple bond). In the absence of a double or triple bond, use “an,” such
as in the case of alkanes.
If there are more than one double or triple bonds in a compound, add prefixes.
2 – di 3 - tri 4 - tetra 5 - penta 6 - hexa 7 - hepta 8 - octa 9 - nona 10 – deca
If the compound has both double and triple bonds, list the double bond and then
the triple bond.
Parent
Straight chain alkanes take the suffix “-ane” and are prefixed depending on the
number of carbon atoms in the chain
If there is a functional group, double bond, or triple bond, (in hierarchical order)
include it in the chain even if this means a shorter carbon chain.
o In the case of several functional groups, refer to functional group
hierarchy as in the table above.
1
2
3
4
5
6
7
8
9
10
11
12
15
20
Meth
Eth
Prop
But
Pent
Hex
Hept
Oct
Non
Dec
Undec
Dodec
Pentadec
Eicos
It is of key importance to number the carbons in the parent chain. A similar
hierarchy is used as when determining the parent chain itself.
If present, the lowest number must be attributed to
1st. Functional Group
a. The number gets placed directly in front of the suffix.
2nd.
Double bond
a. The number indicates the lower number of the two carbon atoms.
3rd.
Triple bond
a. Same as with double bond.
4th.
Substituent (if more than one, label so that substituents get the
lowest numbers possible)
a. The number of the substituent goes immediately in front of the substituent.
b. Every substituent must be numbered and if more than 1 are present, they are
arranged in alphabetical order.
i. Two numbers are separated by commas while letters and numbers are
separated by dashes.
Substituents
Any atoms or groups, other than hydrogen, connected to the parent chain and hierarchical
functional group (if present) are substituents.
• Alkyl groups are named according to the carbon naming table presented
immediately above, together with the “yl” ending. (i.e. methyl, ethyl, propyl)
o If the substituent is not attached to the parent chain by its first carbon, but
rather a middle carbon for example, it is a branched substituent.
 Common examples include:
isopropyl
and
tert-butyl
•
•
•
Halogens are named as substituents by adding the letter “o” at the end.
If the carbons in the parent chain are arranged in a ring, the term “cyclo” must be
added to the beginning of the parent name.
Every substituent needs to be numbered so that its position on the parent chain is
clear.
Stereoisomerism
Stereoisomerism identifies the configuration of any double bonds or stereocenters. Remember that a
stereoisomer is one molecule in a set of isomers that differ by the position of atoms in space, but are not
constitutional isomers or conformational isomers. Stereoisomers are either enantiomers or diastereomers.
•
•
If double bonds are present, they can be arranged in two ways, cis or trans.
(Remember that double bonds cannot freely rotate at room temperature because of
overlapping p orbitals)
o If there are identical groups on the same side of a double bond, it is
labeled as cis, if these identical groups are on other sides it is trans.
 Note- two identical groups attached to the same atom can only
have one configuration and does not need this naming scheme.
o If all four groups attached to the double bond are different there it is
necessary to use Z/E naming, Z (meaning together) and E ( meaning
opposite)
 The priority groups on the two sides of the double bond are
compared, if on the same side then  Z, if they are on the opposite
side then  E
A molecule may have a region (stereocenter) where its atoms can be arranged in
two different configurations, i.e. atoms can be left-handed (S) or right-handed
(R).
•
o If more than one stereocenter is present, numbers must be used to denote
the location of each stereocenter.
o All attached groups to the stereocenter must be different, thus R/S would
never be used to classify a double bond.
o R- means the priority groups are attached in a clockwise fashion
o S- means the priority groups are attached in a counterclockwise fashion.
(+/-) is the direction in which a compound can rotate plane polarized light and is
impossible to predict without a laboratory experiment. This has nothing to do with
(R/S) and is a completely unrelated concept. Enantiomers rotate plane polarized
light in opposite directions, however, it is impossible to make a prediction about
which direction an unknown compound will rotate plane polarized light.
o + means clockwise rotation
o – means counterclockwise rotation
 (+/-) in the beginning of a name implies a racemic mixture (both
enantiomers are present in the solution and the rotations cancel
each other out.
Sources
Key concepts are taken from the recommended organic chemistry supplement:
Klein, David R. Organic Chemistry as a Second Language: First Semester Topics. Hoboken, NJ: Wiley,
2012. Print.
Definitions are from the illustrated glossary by Prof. Steve Hardinger:
Hardinger, Steve. "Dr. Hardinger's Organic Chemistry Page - UCLA." Dr. Hardinger's Organic Chemistry
Page - UCLA. UCLA Chemistry, n.d. Web. 08 June 2012.
<http://www.chem.ucla.edu/harding/index.html>.
Images are from wikipedia