I nternational U nion ofP ure andA ppliedC hemistry
IUPAC Nomenclature of Hydrocarbons
Models Used to Represent Structures
Model ExampleEmpirical molecular formula C7H16
Expanded molecular formula CH3(CH2)5CH3
Structural formula
Condensed structural formula CH3-CH2-CH2-CH2-CH2-CH2-CH3
Line structural formula
Naming Alkanes
• The IUPAC name of any organic compound has three basic parts
Root- denotes number of carbon atoms in the longest continuous chain of carbon atoms
Prefix- gives positions and names of any branches
Suffix- indicates series to which the molecule belongs (e.g. alkane, alkene alkyne)
Root and Side Group Names of Alkanes
Number of Carbon Atoms
Root Name Prefix (Side Group)
1 meth- methyl-
2 eth- ethyl-3 prop- propyl-
4 but- butyl-5 pent- pentyl-
6 hex- hexyl-
7 hept- heptyl-8 oct-
9 non-
10 dec-
The alkanes (CnH2n+2)
Methane (CH4)
Ethane (C2H6)
Propane (C3H8)
Butane (C4H10)
Pentane (C5H12)
Hexane (C6H14)
Heptane (C7H16)
Octane (C8H18)
Nonane (C9H20)
Decane (C10H22)
CH4
CH3 CH3
CH3 CH2 CH3
CH3 CH2 CH2 CH3
CH3 CH2 CH2 CH2 CH3
CH3 CH2 CH2 CH2 CH2 CH3
CH3 CH2 CH2 CH2 CH2 CH2 CH3
CH3 CH2 CH2 CH2 CH2 CH2 CH2 CH3
CH3 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH3
CH3 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH3
Steps for Naming Alkanes
1. Identify the root• Identify the longest
continuous chain• Find the root name for
the number of carbons in the chain
2. Identify the suffix
• Longest chain has 6 carbon atoms
• Root name is hex-• Compound is alkane• Suffix is -ane
1. Identify the prefix (name the branches)
• Identify the number of carbon atoms in each branch
• Determine the name of each branch
• Number the C atoms on the longest chain to produce the lowest number combinations (or sum) for the branches
• Two branches have one carbon atom and 3rd branch has 2 carbon atoms
• Methyl- and ethyl-
• Precede the name of each branch with the number of the carbon atom to which it is attached on the main chain.
• For more than one of the same branch use a prefix: di = 2 ,tri = 3, tetra = 4, penta = 5
• Separate numbers using commas
• Separate numbers and words using hyphens
• 3-ethyl• 2,4-dimethyl
• Arrange branches alphabetically (ignore prefixes di, tri, etc…)
4. Name the compound• Combine prefix, root,
and suffix to name the compound
• Prefix: 3-ethyl-2,4-dimethyl
• Root: hex-• Suffix: -ane• Name: 3-ethyl-2,4-
dimethylhexane
Finding the longest continuous Finding the longest continuous chain chain of carbon atoms is not always of carbon atoms is not always simplesimple
C-C-C-C-C-C-C-C-CC-C-C-C-C-C-C-C-CC
C-C
C-C-CC-C-CC-CC-C
CC-C-C-C-C-CC- C-C-C-C-C-CC-C-C-C-C-C
C-CC-CC-C-C-
C
all possibilitesmust be examined
it won’t always bethe horizontal one as shown here
try these also ……..
99
66 88
CH3 CH2 CH CH3
CH3
Name this alkane
4 3 2 1
2-methylbutane
CH3 CH2 CH CH3
CH2 CH3
Find the longest continuouscarbon chain
1 2 3
4 5
3-methylpentane
CH3 CH2 CH CH2 CH2 CH3
CH2 CH2 CH3
Name the Following Compound
4 3 2 1
5 6 7
4-ethylheptane
CH3 CH2 CH2 CH CH CH2 CH3
CH3
CH2 CH3
Number from the end nearestthe first substituent
7 6 5 4 3 2 1
4-ethyl-3-methylheptane
CH3 CH2 CH2 CH CH2 CH CH2 CH3
CH2 CH3
CH3
Number from the end nearestthe first substituent
8 7 6 5 4 3 2 1
3-ethyl-5-methyloctane
CH3 CH CH CH3
CH3
CH3
Use “di-” with two substituents
1 2 3 4
2,3-dimethylbutane
CH3 CH2 C CH2 CH2 CH3
CH3
CH3
Every substituent must get a number
1 2 3 4 5 6
3,3-dimethylhexane
CH3 CH CH2 C CH3
CH3 CH3
CH3
You need numbers, even though it appears on the same carbon!
5 4 3 2 1
2,2,4-trimethylpentane
CH3 CH2 CH CH CH2 CH2 CH2 CH CH2 CH3
CH3
CH3
CH3
Name the following compound
1 2 3 4 5 6 7 8 9 10
3,4,8-trimethyldecane
CH3 CH2 CH CH CH2 CH CH2 CH3
CH3
CH3
CH2 CH3
Name the following compound Dimethyl alphabetized as methyl, not dimethyl
1 2 3 4 5 6 7 8
6-ethyl-3,4-dimethyloctane
Drawing Alkanes
1. Identify the root• Gives the number of
carbon atoms in the main chain
1. Identify the suffix• Indicates the type of
bond between carbon atoms
3. Draw and number main chain
e.g. draw 3-ethyl-3-methylpentane
root: pent-suffix: -ane
C-C-C-C-C1 2 3 4 5
1. Identify the prefix and draw the side groups
2. Complete the condensed structural formula
Prefix: 3-ethyl-3-methyl-(ethyl and methyl group on carbon 3)
Draw the structural diagram of 2-methylheptane
Physical Properties of Alkanes• Since alkanes are non-polar, they are not soluble
in water
Number of carbon atoms
Boiling point range(oC)
Uses
1 to 4 Below 30 (gases) Fuels to heat homes and cook
5 to 16 30 to 275 (liquids) automotive, diesel and jet engine fuels
16 to 22 Over 250 (heavy liquid) furnace oil
Over 18 Over 400 (Semi-solid) paraffin waxes to make candles
Over 26 Over 500 (Solid residues) asphalts and tars in paving
Naming Alkenes1. Identify the root• Identify longest chain
with a double bond.• Assign root name
based on number of carbons
1. Identify the suffix• Number the main
chain by starting at the end of the chain nearest the double bond.
Root: pent-Suffix: -2-ene
• (indicate the number of the carbon atom that precedes the double bond, only if alkene has 4 or more carbons)
1. Identify the prefix• Name the side groups
on alkenes as you would for alkanes
1. Name the compound.• Combine the prefix,
root and suffix.
Root: pent-Prefix: 2,3-dimethyl-Suffix: -2-ene
Name:2,3-dimethylpent-2-ene
CH2 CH2 CH3 CH CH2
CH3 CH2 CH CH2 CH3 CH CH CH3
ethene propene
but-1-ene but-2-ene
C CH CH3
CH3
CH3
2-methylbut-2-ene
CH3 CH CH2 CH2 CH CH CH3
CH3
6-methylhept-2-ene
C C
CH3
H
CH2
CH2
CH2CH3
CH2CHCH2
CH3
CH3
trans-6-methyl-3-propyloct-2-ene
Drawing Alkenesdraw a structural formula for 2-methylbut-1-ene
• Identify the root• Identify the suffix• Draw and number the
main carbon chain• Identify the prefix and
draw the branches• Complete the
structural formula by adding hydrogens
Root: but- (4 carbons)Suffix: double bond between
c-1 and c-2Prefix: methyl group on c-2
Naming Alkynes1. Identify the root• Identify longest chain
with a triple bond.• Assign root name
based on number of carbons
1. Identify the suffix• Number the main
chain by starting at the end of the chain nearest the triple bond.
Root: pent-Suffix: -1-yne
• (indicate the number of the carbon atom that precedes the triple bond, only if alkyne has 4 or more carbons)
1. Identify the prefix• Name the side groups
on alkynes as you would for alkanes
1. Name the compound.• Combine the prefix,
root and suffix.
Root: pent-Prefix: 3-methyl-Suffix: -1-yne
Name:3-methylpent-1-yne
Drawing Alkynesdraw a structural formula for 3-ethyhex-1-yne
• Identify the root• Identify the suffix• Draw and number the
main chain• Identify the prefix and
draw any side groups• Add enough hydrogen
atoms to give each carbon atom four bonds.
• Root: hex- (6 carbons)• Suffix: -1-yne (triple bond
between c1and c2• Prefix: ethyl group on c3
H C C H CH3 C C H
CH3 CH2 C CH CH3 C C CH3
ethyne propyne
but-1-yne but-2-yne
“acetylene”
ALKYNES ( -YNE )ALKYNES ( -YNE )
C CCH3 CH2CH2CH3
CCH3 C CHCH3
CH3
Hex-2-yne
4-methylpent-2-yne
The suffix hasprecedenceover anybranches
The functional group has precedence in numbering.
functionalgroup
nomenclature of halides and nitro compounds
fluoro chloro bromo iodo
nitro
F Cl Br I
NO2
CH3 C C
CH3
Cl
C CH3
CH3 CH C
CH3
C CH CH2
Br
CH3
4-chloro-4-methylpent-2-yne
5-bromo-2-methylhept-3-yne
Number from the end closest to either the double bondor the triple bond, whichever is closest to the end.
ene vs. yne: which one wins?ene vs. yne: which one wins?
CH3-CH2-C C-CH2-CH=CH-CH3oct-2-en-5-yne
8 7 6 5 4 3 2 1
Compounds are named: en-yne.
cycloalkanes
• The names of the cycloalkanes always contain the prefix cyclo
• Cycloalkanes have the general formulaCnH2n
Cyclic molecules
Cyclopropane
Cyclobutane
Cyclopentane
Cyclohexane
CC
C
H H
H
H
H
H
CH2
CH2
CH2
C
C C
C
H
H
H
H
H
H
H
H
CH2
CH2 CH2
CH2
C
CC
C
C
H HH H
HH
HH
HHCH2
CH2
CH2CH2
CH2
C
CC
C
CC
H HH
H
H
H
HH
H
H
H
HCH2
CH2CH2
CH2
CH2
CH2
Naming Cyclic Hydrocarbons1. Identify the root• Determine number of
carbon atoms in the ring. Assign root name
2. Identify the suffix• Not necessary to
indicate location of double or triple bonds, always between c1-c2
Root: pent-Suffix: -1-yne
• (indicate the number of the carbon atom that precedes the triple bond, only if alkyne has 4 or more carbons)
Naming Cyclic Hydrocarbons
3. Identify the prefix.• If there is only one substituent, do not use the “1”. • If there is more than one substituent, you must use all
numbers, including “1”!• If there are two or more side groups, the numbering must
start with a side group and then proceed in the direction that gives the lowest possible numbers to all the side groups.
• If numbers are the same for two or more side groups, the side group that comes first alphabetically is assigned as c-1.
Naming Cyclic Hydrocarbons
• If the molecule is a cyclic alkene or cyclic alkyne, the multiple bond takes highest priority. The carbon atom on one side of the multiple bonds is c-1 and one the other side is c-2. If there are side groups, the numbering starts in the position that will make the number of the carbon atoms bonded to the side groups as small as possible.
4. Name the compound• Combine the prefix, root, and suffix to name the
compound.
Naming Cyclic Hydrocarbons
1. Root: cyclopent2. Suffix:-ene3. Prefix:3,4-dimethylName:3,4-dimethylcyclopentene
CH3
CH3
1,1-dimethylcyclohexane
CH3
CH3
CH2CH3
4-ethyl-1,1-dimethylcyclohexane
CH3
CH3
CH3
CH3CH3
CH2CH3
CH3
CH3
CH3CH2
1,3-dimethylcyclopentane
1-ethyl-4-methylcyclohexane3-ethyl-1,1-dimethylcyclobutane
Some cycloalkanesSome cycloalkanes
The more substituted carbontakes precedence even though E comes before M.
Drawndifferentlybut samename.=
E before M
1 23
12
3
1
2312
34
Numbering starts at the most highly-substituted carbon
Cl CH3
CH3
CH3
2 13 74 6 5
2-chloro-1,1,6-trimethylcycloheptane
cycloalkyl groups
cyclopropyl cyclobutyl
cyclopentyl cyclohexyl
C
CH3
CH2CH2CH3 CH3
3-cyclobutyl-3-methylpentane
Another name of a group
or
Phenyl
or C6H5
CH3 CH2 CH CH CH3
CH3
3-methyl-2-phenylpentane