IUPAC Rules

In order to name organic compounds you must first memorize a few

basic names. These names are listed within the discussion of naming
alkanes. In general, the base part of the name reflects the number of
carbons in what you have assigned to be the parent chain. The
suffix of the name reflects the type(s) of functional group(s) present
on (or within) the parent chain. Other groups which are attached to
the parent chain are called substituents.

Alkanes - saturated hydrocarbons

The names of the straight chain saturated hydrocarbons for up
to a 12 carbon chain are shown below. The names of the
substituents formed by the removal of one hydrogen from the
end of the chain is obtained by changing the suffix -ane to -yl.

Number of Carbons Name

1 methane
2 ethane
3 propane
4 butane
5 pentane
6 hexane
7 heptane
8 octane
9 nonane
10 decane
11 undecane
12 dodecane

There are a few common branched substituents which you

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 should memorize. These are shown below.

Here is a simple list of rules to follow. Some examples are given

at the end of the list.

1. Identify the longest carbon chain. This chain is called the

parent chain.

2. Identify all of the substituents (groups appending from the

parent chain).

3. Number the carbons of the parent chain from the end that
gives the substituents the lowest numbers. When
compairing a series of numbers, the series that is the
"lowest" is the one which contains the lowest number at
the occasion of the first difference. If two or more side
chains are in equivalent positions, assign the lowest
number to the one which will come first in the name.

4. If the same substituent occurs more than once, the location

of each point on which the substituent occurs is given. In
addition, the number of times the substituent group occurs
is indicated by a prefix (di, tri, tetra, etc.).

5. If there are two or more different substituents they are

listed in alphabetical order using the base name (ignore the
prefixes). The only prefix which is used when putting the
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 substituents in alphabetical order is iso as in isopropyl or
isobutyl. The prefixes sec- and tert- are not used in
determining alphabetical order except when compared with
each other.

6. If chains of equal length are competing for selection as the

parent chain, then the choice goes in series to:
a) the chain which has the greatest number of side chains.
b) the chain whose substituents have the lowest- numbers.
c) the chain having the greatest number of carbon atoms in
the smaller side chain.
d)the chain having the least branched side chains.

7. A cyclic (ring) hydrocarbon is designated by the prefix

cyclo- which appears directly in front of the base name.

In summary, the name of the compound is written out with the

substituents in alphabetical order followed by the base name
(derived from the number of carbons in the parent chain).
Commas are used between numbers and dashes are used
between letters and numbers. There are no spaces in the name.

Here are some examples:

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 Alkyl halides
The halogen is treated as a substituent on an alkane chain. The
halo- substituent is considered of equal rank with an alkyl
substituent in the numbering of the parent chain. The halogens
are represented as follows:

F fluoro-
Cl chloro-
Br bromo-
I iodo-

Here are some examples:

Alkenes and Alkynes - unsaturated hydrocarbons

Double bonds in hydrocarbons are indicated by replacing the
suffix -ane with -ene. If there is more than one double bond,
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 the suffix is expanded to include a prefix that indicates the
number of double bonds present (-adiene, -atriene, etc.).
Triple bonds are named in a similar way using the suffix -yne.
The position of the multiple bond(s) within the parent chain
is(are) indicated by placing the number(s) of the first carbon of
the multiple bond(s) directly in front of the base name.

Here is an important list of rules to follow:

1. The parent chain is numbered so that the multiple bonds

have the lowest numbers (double and triple bonds have
priority over alkyl and halo substituents).

2. When both double and triple bonds are present, numbers

as low as possible are given to double and triple bonds
even though this may at times give "-yne" a lower number
than "-ene". When there is a choice in numbering, the
double bonds are given the lowest numbers.

3. When both double and triple bonds are present, the -en
suffix follows the parent chain directly and the -yne suffix
follows the -en suffix (notice that the e is left off, -en
instead of -ene). The location of the double bond(s) is(are)
indicated before the parent name as before, and the
location of the triple bond(s) is(are) indicated between the
-en and -yne suffixes. See below for examples.

4. For a branched unsaturated acyclic hydrocarbon, the

parent chain is the longest carbon chain that contains the
maximum number of double and triple bonds. If there
are two or more chains competing for selection as the
parent chain (chain with the most multiple bonds), the
choice goes to (1) the chain with the greatest number of
carbon atoms, (2) the # of carbon atoms being equal, the
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 chain containing the maximum number of double bonds.

5. If there is a choice in numbering not previously covered, the

parent chain is numbered to give the substituents the
lowest number at the first point of difference.

Here are some examples:

Alcohols
Alcohols are named by replacing the suffix -ane with -anol. If
there is more than one hydroxyl group (-OH), the suffix is
expanded to include a prefix that indicates the number of
hydroxyl groups present (-anediol, -anetriol, etc.). The position
of the hydroxyl group(s) on the parent chain is(are) indicated by
placing the number(s) corresponding to the location(s) on the
parent chain directly in front of the base name (same as
alkenes).

Here is an important list of rules to follow:

1. The hydroxyl group takes precedence over alkyl groups

and halogen substituents, as well as double bonds, in the
numbering of the parent chain.
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 2. When both double bonds and hydroxyl groups are present,
the -en suffix follows the parent chain directly and the -ol
suffix follows the -en suffix (notice that the e is left off, -en
instead of -ene). The location of the double bond(s) is(are)
indicated before the parent name as before, and the
location of the hydroxyl group(s) is(are) indicated between
the -en and -ol suffixes. See below for examples. Again, the
hydroxyl gets priority in the numbering of the parent chain.

3. If there is a choice in numbering not previously covered, the

parent chain is numbered to give the substituents the
lowest number at the first point of difference.

Here are some examples:

Ethers
You are only expected to know how to name ethers by their
commmon names. The two alkyl groups attached to the oxygen
are put in alphabetical order with spaces between the names
and they are followed by the word ether. The prefix di- is used if
both alkyl groups are the same.

Here are some examples:

Aldehydes
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 Aldehydes are named by replacing the suffix -ane with -anal. If
there is more than one -CHO group, the suffix is expanded to
include a prefix that indicates the number of -CHO groups
present (-anedial - there should not be more than 2 of these
groups on the parent chain as they must occur at the ends). It is
not necessary to indicate the position of the -CHO group
because this group will be at the end of the parent chain and its
carbon is automatically assigned as C-1.

Here is an important list of rules to follow:

1. The carbonyl group takes precedence over alkyl groups

and halogen substituents, as well as double bonds, in the
numbering of the parent chain.

2. When both double bonds and carbonyl groups are present,

the -en suffix follows the parent chain directly and the -al
suffix follows the -en suffix (notice that the e is left off, -en
instead of -ene). The location of the double bond(s) is(are)
indicated before the parent name as before, and the -al
suffix follows the -en suffix directly. Remember it is not
necessary to specify the location of the carbonyl group
because it will automatically be carbon #1. See below for
examples. Again, the carbonyl gets priority in the
numbering of the parent chain.

3. There are a couple of common names which are

acceptable as IUPAC names. They are shown in the
examples at the end of this list but at this point these
names will not be accepted by the computer. Eventually
they will be accepted.

4. If there is a choice in numbering not previously covered, the

parent chain is numbered to give the substituents the
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 lowest number at the first point of difference.

Here are some examples:

Ketones
Ketones are named by replacing the suffix -ane with -anone. If
there is more than one carbonyl group (C=O), the suffix is
expanded to include a prefix that indicates the number of
carbonyl groups present (-anedione, -anetrione, etc.). The
position of the carbonyl group(s) on the parent chain is(are)
indicated by placing the number(s) corresponding to the
location(s) on the parent chain directly in front of the base name
(same as alkenes).

Here is an important list of rules to follow:

1. The carbonyl group takes precedence over alkyl groups

and halogen substituents, as well as double bonds, in the
numbering of the parent chain.

2. When both double bonds and carbonyl groups are present,

the -en suffix follows the parent chain directly and the -one
suffix follows the -en suffix (notice that the e is left off, -en
instead of -ene). The location of the double bond(s) is(are)
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 indicated before the parent name as before, and the
location of the carbonyl group(s) is(are) indicated between
the -en and -one suffixes. See below for examples. Again,
the carbonyl gets priority in the numbering of the parent
chain.

3. If there is a choice in numbering not previously covered, the

parent chain is numbered to give the substituents the
lowest number at the first point of difference.

Here are some examples:

Carboxylic Acids
Carboxylic acids are named by counting the number of carbons
in the longest continuous chain including the carboxyl group
and by replacing the suffix -ane of the corresponding alkane
with -anoic acid. If there are two -COOH groups, the suffix is
expanded to include a prefix that indicates the number of -
COOH groups present (-anedioic acid - there should not be
more than 2 of these groups on the parent chain as they must
occur at the ends). It is not necessary to indicate the position of
the -COOH group because this group will be at the end of the
parent chain and its carbon is automatically assigned as C-1.

Here is an important list of rules to follow:

1. The carboxyl group takes precedence over alkyl groups

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 and halogen substituents, as well as double bonds, in the
numbering of the parent chain.

2. If the carboxyl group is attached to a ring the parent ring is

named and the suffix -carboxylic acid is added.

3. When both double bonds and carboxyl groups are present,

the -en suffix follows the parent chain directly and the -oic
acid suffix follows the -en suffix (notice that the e is left off,
-en instead of -ene). The location of the double bond(s)
is(are) indicated before the parent name as before, and the
-oic acid suffix follows the -en suffix directly. Remember it
is not necessary to specify the location of the carboxyl
group because it will automatically be carbon #1. See below
for examples. Again, the carboxyl gets priority in the
numbering of the parent chain.

4. There are several common names which are acceptable as

IUPAC names. They are shown in the examples at the end
of this list but at this point these names will not be
accepted by the computer. Eventually they will be
accepted.

5. If there is a choice in numbering not previously covered, the

parent chain is numbered to give the substituents the
lowest number at the first point of difference.

Here are some examples:

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 Esters
Systematic names of esters are based on the name of the
corresponding carboxylic acid. Remember esters look like this:

The alkyl group is named like a substituent using the -yl ending.
This is followed by a space. The acyl portion of the name (what
is left over) is named by replacing the -ic acid suffix of the
corresponding carboxylic acid with -ate.

Here are some examples:

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 Amines
You are only expected to know how to name amines by their
common names . They are named like ethers, the alkyl (R)
groups attached to the nitrogen are put in alphabetical order
with no spaces between the names and these are followed by
the word amine. The prefixes di- and tri- are used if two or three
of the alkyl groups are the same.
NOTE: Some books put spaces between the parts of the name,
but we will not. Follow the examples.

Here are some examples:

Summary of functional groups

Functional group Prefix Suffix

carboxylic acids none -oic acid
aldehydes none -al
ketones none -one
alchols hydroxy- -ol
amines amino- -amine
ethers alkoxy- -ether
fluorine fluoro- none

chlorine chloro- none

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 bromine bromo- none
iodine iodo- none
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