Nomenclature

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Section 2: Nomenclature
IUPAC name features
Let’s look at an example:
Here the substituent is circledthere is a single C with 3
hydrogens = methyl.
1
2
4
3
5
And the carbons in the
longest (i.e. parent) chain
are numbered, starting at
the end nearest the
substituent.
So how do we name this compound?
1
2
4
2-methylpentane
3
5
Substituent
Locant – indicates the
substituent, ‘methyl’, is
on the 2nd carbon in the
parent chain
Infix – ‘an’ indicates the C-C
bonds are single bonds
2-methylpentane
Parent – indicates the longest
C chain contains 5 carbon.
Suffix – ‘e’ indicates this is a
hydrocarbon compound (as
opposed to e.g. an alcohol
when suffix ‘ol’ would be
used.
So how do we name this compound?
Substituent
= bromine
= ‘bromo’
Infix – ‘an’ indicates the C-C
bonds are single bonds
4-bromoheptane
4-bromoheptane
Locant – indicates the
substituent, a bromine, is
on the 4nd carbon in the
parent chain*
Parent – indicates the longest
C chain contains 7 carbon.
Suffix – ‘e’ indicates this is a
hydrocarbon compound (as
opposed to e.g. an alcohol
when suffix ‘ol’ would be
used.
* Note: in this case it doesn’t matter from which end we start numbering the C atoms because the Br is on the 4th C either way.
Naming bicyclic alkanes: bridged
So how do we name this compound
which has two rings in it?
Bridgehead
Bridge
Let’s first identify some key
features:
Bridgehead
So we have a compound with 2 bridgeheads and 3
bridges. The left and right bridges each contain 2
carbons, the middle bridge only 1 carbon
Naming bicyclic alkanes
So how do we name this compound?
‘hept’ indicates 7 carbons
total, ‘an’ indicates single CC bonds, ‘e’ indicates
hydrocarbon compound.
Bicyclo[2.2.1]heptane
Bicyclo[2.2.1]heptane
This tells us that there are 2 rings
in the structure
The numbers in the brackets tell us how many
carbons are in the 3 bridges, always placed in
descending order. Because the middle bridge has at
least 1 carbon in it this is known as a bridged
bicyclic alkane
Naming bicyclic alkanes: fused
So how do we name this compound
which has no carbons in the middle
bridge?
‘dec’ indicates 10 carbons
total, ‘an’ indicates single CC bonds, ‘e’ indicates
hydrocarbon compound.
Bicyclo[4.4.0]decane
Bicyclo[4.4.0]decane
This tells us that there are 2 rings
in the structure
The last number is a 0 because the
middle bridge contains no carbons.
This is therefore an example of a fused
bicyclic alkane.
Naming bicyclic alkanes: spiro
‘oct’ indicates 8 carbons
total, ‘an’ indicates single CC bonds, ‘e’ indicates
hydrocarbon compound.
So how do we name this compound
which has a single shared C atom?
spiro[3.4]octane
spiro[3.4]octane
This tells us that there are 2 rings
in the structure which share a
single C atom.
This tells us how many carbons are in
each ‘link’ or ring, other than the
spiro (central, shared) carbon. Here
put in ascending order.
Naming bicyclic alkanes with substituents
So how do we name this compound
which has a substituent on one of its
carbons?
1
6
2
7
Here we will need to number the carbons
in the rings so we can identify which C the
substituents are attached to:
1. Start at one bridgehead
2. Work round the longest bridge
3. Then the next longest bridge
4. Then the final bridge (do not renumber
the bridgeheads as you pass over them
again)
3
5
4
Substituents = 2
x methyl on the
same carbon.
Naming bicyclic alkanes with substituents
So how do we name this compound
which has substituents on one of its
carbons?
7,7-dimethylbicyclo[2.2.1]heptane
7,7-dimethylbicyclo[2.2.1]heptane
This tells us that there are two
methyl groups, each on carbon 7
As before
Naming bicyclic alkanes with substituents
Substituent =
methyl
So how do we name this spiro
compound which has a substituent on
one of its carbons?
6
7
2
4
8
Here we will need to number the carbons in the
rings so we can identify which C the substituents
are attached to.
1. Start in the smallest link or ring, with a
carbon adjacent to the spiro carbon
2. Then the next link or ring
3. Numbering so as to give any substituents the
lowest possible locants.
1
5
3
9
I.e. NOT 8
9
7
1
2
4
6
5
3
Naming bicyclic alkanes with substituents
So how do we name this compound
which has a substituent on one of its
carbons?
5-methylspiro[3.5]nonane
This tells us that the methyl
group is on the 5th carbon
As before
E,Z System
How do we name this compound?
High priority
Low priority – carbon from
methyl has higher priority than H
Low priority –
methyl has lower
priority than Cl
because Cl has a
higher atomic
number than C
High priority
The high priority groups are on opposite
sides of the double bond hence (E)-2chloro-2-butene
How do we name this compound?
High priority
High priority
Low priority
Low priority –I
has a higher
atomic number
than C
The high priority groups are on the same
sides of the double bond hence (Z)-2iodo-2-pentene
How do we name this compound?
High priority
High priority
Low priority Low priority
High priority
Low priority
Low priority
High priority
If there is more than one double C-C bond we need to
indicate to which the E and Z apply using the number
of the first C in that double bond.
This is (1Z,3E)-1-bromo-1,3-pentadiene
Naming polysubstituted benzenes
So how do we name this compound?
Remember: We need to number the ring so
as to give the substituents the lowest set of
numbers possible and any monosubstituted compound can serve as the
parent name.
3
4
2
5
6
1
4-bromo-1,2-dimethylbenzene
OR….
So how do we name this compound?
Remember: We need to number the ring so
as to give the substituents the lowest set of
numbers possible and any monosubstituted compound can serve as the
parent name.
3
4
2
5
= toluene = the methyl that is part
of toluene is automatically carbon
number 1.
1
6
4-bromo-2-methyltoluene
NOT….
5
6
2
1
4
2
3
5-bromo-1,2-dimethylbenzene
1
6
3
4
5
1-bromo-3,4-dimethylbenzene
These names are incorrect because the
substituents are not on the lowest possible
numbered carbons.
So how do we name this compound?
Remember: We need to number the ring so
as to give the substituents the lowest set of
numbers possible and any monosubstituted compound can serve as the
parent name.
3
4
2
5
6
1
4-bromo-1,2-dimethylbenzene
OR….
Naming esters
So how do we name this compound?
Remember: names of esters are based on
the parent alcohol and carboxylic acid they
are derived from.
First part of the name (alkyl) is based on
alcohol.
Second part (--oate) is based on the
carboxylic acid.
carboxylic acid = 2
carbons = ethanoic acid
ethanoate
alcohol = 2 carbons =
ethanol
 ethyl
Ethyl ethanoate
So how do we name this compound?
Remember: names of esters are based on
the parent alcohol and carboxylic acid they
are derived from.
First part of the name (alkyl) is based on
alcohol.
Second part (--oate) is based on the
carboxylic acid.
Part of carboxylic acid =
cyclohexancarboxylic
acid

cyclohexanecarboxylate
Part of alcohol = tertbutyl alkyl group
Tert-butyl cyclohexanecarboxylate
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