Naming Hydrocarbons
(nomenclature)
Drawing Structures: It’s All Good
H
C
2-butene
H
H
H
C
C
C
C
H
H
H
H
H3C
H
H 3C CH CH CH 3
CH
H3C
CH3
C
H
CH3
CH
CH3
H3C
This is called the
“condensed structure”
CH3CH=CHCH3
Using brackets can also shorten some formulas:
CH3CH2CH2CH2CH2CH3 vs. CH3(CH2)4CH3
Basic Naming of Hydrocarbons
Hydrocarbon names are based on: 1) type,
2) # of carbons, 3) side chain type and position
1) name will end in -ane, -ene, or -yne
2) the number of carbons is given by a “prefix”
1 meth- 2 eth- 3 prop- 4 but- 5 pent6 hex- 7 hept- 8 oct- 9 non- 10 decActually, all end in a, but a is dropped when next
to a vowel. E.g. a 6 C alkene is hexene
Q - What names would be given to these:
7C, 9C alkane heptane, nonane
2C, 4C alkyne ethyne, butyne
1C, 3C alkene methene, propene
Mnemonic for First Four Prefixes
First four prefixes
•
•
•
•
MethEthPropBut-
Monkeys
Eat
Peeled
Bananas
Other Prefixes
Decade
?
Decimal
• Pent• Oct-
• Dec-
Decathalon • Hex-, Hept-, NonMother Eats Peanut Butter Pickles Having Ham On Numbered Dishes
1. What are the 3 classes of hydrocarbons, based
on number of carbon-carbon bonds?
2. Give the 10 organic homologous prefixes, in
order, from 1-10.
3. Name these compounds:
H3C
H 3C
C
H
C2H4
H
C
CH3
CH3
Numbering Carbons
Q- draw 1-pentene
A- Where’s the double H3C
5
1
bond? We # C atoms.
•
•
•
•
H
H
1-pentene
C
C
C
4
2
3
2
4
C
1
5
H
H H H H
Naming compounds with multiple bonds is more
complex than previously indicated.
When 2+ possibilities exist, #s are needed.
Always give double bond the lowest number.
Q - Name these
H
H H
H
H3 C
C
C
C
C
C
H H
H H
H
C H3
H
C
H
C
C
H
1. Name the 4 groups of hydrocarbons.
(alphabetically)
2. Draw the structures for the following
compounds:
A. 2-octene
B. 4-decyne
C. hexane
D. 3, 4, 5 – triethyldecane
E. 2-chloro – 4 – methyl – nonane
Naming Side Chains
CH3
• The names of molecules H C
CH33
3
with branches are based
on: side chains, root
CH3
2,3-dimethylpentane
• The “root” or “parent chain” is usually the
longest possible hydrocarbon chain.
• The root must include multiple bonds if they are
present. If a cyclic structure is present it will be
the root even if it is not the longest chain.
• Side chains are also called “side branches” or
“alkyl groups”. Their names end in -yl.
Common side chains :
-CH3 methyl, -CH2CH3 ethyl, -CH2CH2CH3 propyl
IUPAC Rules for Naming Hydrocarbons
1. Choose the correct ending: -ane, -ene, or -yne
2. Determine the longest carbon chain. Where a
double or triple bond is present, choose the
longest chain that includes this bond. If there is a
cyclic structure present, the longest chain starts
and stops within the cyclic structure.
3. Assign numbers to each C of the parent chain.
For alkenes and alkynes the first carbon of the
multiple bond should have the smallest number.
For alkanes the first branch (or first point of
difference) should have the lowest #. Carbons in a
multiple bond must be numbered consecutively.
4. Attach a prefix that corresponds to the number of
carbons in the parent chain. Add cyclo- to the
prefix if it is a cyclic structure.
IUPAC Rules for Naming Hydrocarbons
5. Determine the correct name for each branch
(“alkyl” groups include methyl, ethyl, propyl, etc.)
6. Attach the name of the branches alphabetically,
along with their carbon position, to the front of the
parent chain name. Separate numbers from
letters with hyphens (e.g. 4-ethyl-2-methyldecane)
7. When two or more branches are identical, use
prefixes (di-, tri-, etc.) (e.g. 2,4-dimethylhexane).
Numbers are separated with commas. Prefixes
are ignored when determining alphabetical order.
(e.g. 2,3,5-trimethyl-4-propylheptane)
8. When identical groups are on the same carbon,
repeat the number of this carbon in the name.
(e.g. 2,2-dimethylhexane)
Naming Side Chains
Example: use the rules on this handout
to name the following structure
CH2
CH3 CH2 C
CH2 CH3
CH2 C
CH3
CH3
Rule 1: choose the correct ending
ene
Naming Side Chains
CH2
CH3 CH2 C
CH2 CH3
CH2 C
CH3
CH3
Rule 2: determine the longest carbon chain
ene
Naming Side Chains
CH2
CH3 CH2 C
CH2 CH3
CH2 C
CH3
CH3
Rule 3: Assign numbers to each carbon
ene
Naming Side Chains
CH2
CH2 CH3
1
CH3 CH2 C
2
5
CH2 C
3
4
6
CH3
CH3
Rule 3: Assign numbers to each carbon
ene
Naming Side Chains
CH2
CH2 CH3
1
CH3 CH2 C
2
5
CH2 C
3
4
6
CH3
CH3
Rule 4: attach prefix (according to # of Cs)
1-hexene
ene
Naming Side Chains
CH2
ethyl
CH2 CH3
1
CH3 CH2 C
2
5
CH2 C
3
4
CH3
6
CH3
methyl
methyl
Rule 5: Determine name for side chains
1-hexene
Naming Side Chains
CH2
ethyl
CH2 CH3
1
CH3 CH2 C
2
5
CH2 C
3
4
CH3
6
CH3
methyl
methyl
Rule 6: attach name of branches alphabetically
2-ethyl-4-methyl-4-methyl-1-hexene
1-hexene
Naming Side Chains
CH2
ethyl
CH2 CH3
1
CH3 CH2 C
2
5
CH2 C
3
4
CH3
6
CH3
methyl
methyl
Rule 7,8: group similar branches
2-ethyl-4-methyl-4-methyl-1-hexene
1-hexene
Naming Side Chains
CH2
ethyl
CH2 CH3
1
CH3 CH2 C
2
5
CH2 C
3
4
CH3
6
CH3
methyl
methyl
Rule 7,8: group similar branches
2-ethyl-4,4-dimethyl-1-hexene
CH3 CH CH2
CH3
propene
CH3
CH
CH3
CH
C
CH3
CH3 CH CH CH3
2,4-dimethyl-2-pentene
2-butene
CH
C
CH2 CH3
1-butyne
CH3
CH2 CH
C
CH3
CH2 CH3
CH3
CH3
C
CH
CH2
CH3
b) same
CH3
C
CH
CH2
a) 3,3-dimethyl-1-pentene
CH3
C
CH3
CH
CH2
CH2 CH3
c) 5-ethyl-4-methyl-2-heptyne
For more lessons, visit
www.chalkbored.com
Draw
• 3 – methyl-1,3-cyclopentene
• 2-ethyl-2-pentene
Name:
5.
3.
4.
Give both
names!
Isomers
Same molecular formula, different molecular structures.
Two types: structural and geometric isomers.
1. Structural Isomers: molecules with same chemical
formula, but different molecular structures.
CH3
CH3-CH2-CH2-CH3
CH3-CH-CH3
butane (C4H10)
2 – methylpropane (C4H10)
Isomers (cont’d)
2. Geometric Isomers: differ only in the geometry of their
substituted groups.
cis- 2 - butene
trans- 2 - butene
cis-configuration: substituted groups are on the same side as the
double bond.
trans-configuration: substituted groups are on the opposite sides
of the double bond.
1. Draw the structural formulas:
3. Name the following:
a) 3-ethyl-1,4-cyclopentene
H
H
b) 1-chloro-2,3,4-triethyl-3-heptene a)
C=C
CH3
CH2CH2CH3
c) 2-fluoro-7,7-dimethyl-4-decyne
CH3
CH3
2. Draw the cis and trans forms of the b)
C=C
CH3
CH3
following alkenes:
a) 2-pentene
4. Identify the asymmetric
b) 2-octene
carbon, if any:
c) 2-methyl-2-heptene
a) CH3CH2CHO
d) 2,3-dimethyl-2-butene
b) CH3CHOH
CH3
Isomers (cont’d)
Stereoisomers: molecules of the same molecular structure that
differ only in the arrangement of the atoms in space. They are
mirror images of each other (think right and left hands.)
Isomers (cont’d)
Stereoisomers: molecules of the same molecular structure that
differ only in the arrangement of the atoms in space. They are
mirror images of each other (think right and left hands.)
Left-handed (S)
Isomers (cont’d)
Stereoisomers: molecules of the same molecular structure that
differ only in the arrangement of the atoms in space. They are
mirror images of each other (think right and left hands.)
Left-handed (S)
Right-handed (R)
Isomers (cont’d)
Stereoisomers: molecules of the same molecular structure that
differ only in the arrangement of the atoms in space. They are
mirror images of each other (think right and left hands.)
“left-handed”
“right-handed”
Aromatic Hydrocarbons
Aromatic hydrocarbons are hydrocarbons that have six-membered
carbon rings and delocalized electrons. Benzene is the primary
aromatic hydrocarbon.
Benzene has the chemical formula C6H6 and can also be thought of
as 1,3,5-cyclohexatriene (hexene).
Benzene can also be represented graphically like this.
Isomers (cont’d)
Asymmetric Carbon: a carbon with four different groups attached to it.
Cl
H
C
Br
F
Chlorofluorobromomethane
Functional Groups
• Besides our basic hydrocarbon classes, we can add
other elements/ions, groups of elements to an
organic structure = Functional Groups
• R = radical or, in this case, represents C
• Alcohols (R-OH), ethers (R-O-R), carboxylic
acids (R-COOH), aldehydes (R-COH) – what are
the others presented in the book?
• Identifying these!
• Naming these (all have their own endings)!
Classes of Organic Compounds
A functional group gives an organic compound properties that are
very different from those of corresponding hydrocarbons.
Some examples:
1. Alcohols: are organic compounds that contain one or more
hydroxyl groups. The general formula for alcohols is
R-OH (rememeber that “R” stands for the rest of the
molecule.)
Glycerol:
1,2,3-propanetriol
Ethanol:
1-ethanol
Classes of Organic Compounds (cont’d)
2. Ethers: are organic compounds in which two hydrocarbon
groups are bonded to the same oxygen atom. This can
can be represented by the formula R-O-R.
Diethyl Ether:
Dioxane:
Dimethyl Ether:
Classes of Organic Compounds (cont’d)
3. Aldehydes and ketones: contain the carbonyl group:
Aldehyde
Ketone
Aldehyde: organic compound in which the carbonyl group is
attached to a carbon atom at the end of a carbon chain.
Ketone: organic compound in which the carbonyl group is
attached to carbon atoms within the chain.
Classes of Organic Compounds (cont’d)
4. Carboxylic Acids: are organic compounds that contain the
carboxyl functional group. A member of this class of organic
compounds can be represented by the general formula:
5. Esters: are organic compounds that have carboxylic acid groups
in which the hydrogen of the hydroxyl group has been replaced
by an alkyl group. Observe:
Classes of Organic Compounds (cont’d)
Many esters have distinctive fruit-like odors, which has led to their
commonplace use in artificial flavorings and fragrances. Examples: