IUPAC HYDROCARBON NOMENCLATURE
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Hydrocarbons are molecules that consist of only carbon and hydrogen atoms.
They can be linear or cyclic.
They can contain single, double, or triple bonds.
Alkane Nomenclature
• contain ONLY single bonds and are identified by the suffix “– ane”
Name this molecule: (Condensed structural diagram)
Step
Instruction
Example
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1
Find the longest carbon chain
(parent chain)
2
# carbons in parent chain starting
from the carbon closest to a side
chain (branch)
3
Choose one of the following options
to finish naming:
a. ONE BRANCH
#-(branch name)(parent chain)
b. MORE THAN 1 BRANCH
list them in alphabetical order
(even though they may not be in
numeric order).
#-alpha1-#-alpha2prefixane
___________ long
This number will provide the prefix for the main
carbon chain – in this case _______
1
meth2
eth3
prop4
but5
pent6
hex7
hept8
oct9
non10
dec-
c. CYCLIC HYDROCARBON
• the carbon atoms that form the
ring are the parent chain;
• put the prefix cyclo- in front of
the name of the parent chain.
• Naming the branches follows
the same rules as the linear
hydrocarbons.
#-alpha1-#-alpha2cycloprefixane
d. MULTIPLE IDENTICAL
BRANCHES
•
indicate how many
branches there are using
the prefixes di-, tri-, tetraand indicate their location
numerically.
#,#,#-tribranchprefixane
4
Check for proper punctuation
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__________ separate _____________
_________ separate a ______________________
___________ between letters
PRACTICE!!
Name these molecules:
Draw these molecules:
3,3-dimethylheptane
3-ethyl-pentane
cyclohexane
Special case: Naming propyl and butyl groups
When an alkyl group has 3 or more C atoms, it may attach to the parent chain at
any of its carbons.
There are two isomers of the propyl group:
a) CH3 – CH2 – CH2
b) CH3 – CH – CH3
n-propyl (normal propyl)
isopropyl
There are 4 isomers of the butyl group:
a) CH3 – CH2 – CH2 – CH2
b) CH3 – CH – CH3
n-butyl
CH2
]
isobutyl
c) CH3 – CH – CH2 – CH3
s-butyl
d)
CH3
CH3 – C – CH3
t-butyl
*branch spelling takes alphabetical priority over type (n, s, t, iso)
PRACTICE!
CH3
CH3CH2CHCHCH2CH2CH3
CH3CHCH3
4-s-butyl-4,6-diethyldecane
(line diagram)
Alkenes and Alkynes Nomenclature
1.
2.
3.
4.
5.
The parent chain is either the alkene (double bond) or the alkyne (triple
bond).
When numbering the carbons on the parent chain, begin with the end that
will give the double or triple bond the lower number.
The location of the multiple bond is indicated by the number of the carbon
atom that begins the multiple bond.
The presence and location of more than one multiple bond is shown by the
prefixes di-, tri, tetra- just before the -ene or -yne ending of the parent chain.
If the hydrocarbon is cyclic, the prefix cyclo precedes the name of
the parent chain.
Practice!
2-methyl-1,3-pentadiene
3,3-dimethyl-1-butyne
CH2=CH-C=CH-CH2-CH3
CH3-CH-CH3
Isomerism
There are 2 types of isomers that we deal with in this course: ________________
and ________________________
___________________________________
• organic compounds with the same _______________, but with differing
______________________________.
• results in different _________________________ properties
• may be _______________________ bonds present
What is the molecular formula for the above isomers? _____________
________________________________________
• organic compounds with the same ____________________ and the same
________________ (all atoms connected in the same way), but there is a
different ____________________________________________.
• occurs due to the __________________________________.
• tend to have the same _____________________, but may have very different
physical properties eg. m.p.
Aromatic Nomenclature
Normally in aromatic nomenclature, benzene is treated and named as the parent
chain, but if it is attached to a much more complicated alkyl group it is treated as a
branch and called “phenyl”
Example:
methylbenzene
2-phenylhexane