hydrocarbons module 9: hydrocarbons alkanes alkenes alkynes aromatic hydrocarbons
TRANSCRIPT
Four bonds in Carbon
C C
4 single bonds 1 double bond and 2 single
bonds
2 double bonds
1 triple bond and
1 single bond
C
Types of Hydrocarbons
Saturated hydrocarbons - contain only single bonds
Example - alkanes
Unsaturated hydrocarbons – contain double or triple bonds between the carbon atoms.
Examples – alkenes, alkynes
Structural, Condensed, and Molecular Formulas for Simple Alkanes
HH
H
C - H
H HH
H
H
H
H
H
C - C - C
Carbon BackboneStructural Formula
Condensed Formula MolecularFormula
- C - CH4 CH4
C - C CH3-CH3 C2H6
C - C - C CH3-CH2-CH3
C3H8
C - C - C - C
CH3-CH2-CH2-CH3
C4H10
C - C - C - C - C CH3-CH2-CH2-CH2-CH3 C5H12
The Alkane Series# of C name # of C name
1 methane 6 hexane
2 ethane 7 heptane
3 propane 8 octane
4 butane 9 nonane
5 pentane 10 decane
Nomenclature of Alkanes
Alkyl GroupsCH3
- CH - CH3methyl ethyl propyl isopropyl
-CH3 -CH2-CH3 -CH2-CH2-CH3
CH3
-CH-CH3
Alkyl groups
Nomenclature of Alkanes
Alkanes are named according to the number of carbon atoms in the longest continuous chain or parent chain.
To name an alkane, the parent chain must be located first.
If there Is branching then the chain is numbered so that the branch (or branches) get the lowest possible number.
Nomenclature of Alkanes
Example: Name the following compound.
The longest continuous chain consists of 5 carbon atoms, therefore the parent chain is pentane and the branch is attached to the second carbon in the chain.
CH2 - CH - CH 4
CH3
2 - CH33 2 1
CH -35
Nomenclature of Alkanes
Example: Name the following compound.
2 – methylpentane
CH2 - CH - CH 4
CH3
2 - CH33 2 1
CH -35
Haloalkanes or alkyl halides
fluoro = -F chloro = -Cl bromo = -Br iodo = -I
When a halogen is present in a compound, it is called a halogenated hydrocarbon
Haloalkanes or alkyl halides
Example:
CH2 - CH2 - CH2 - CH2 - CH3
CH2 - CH2 - CH2 - CH3
5
9 106 7 8
4 3 1
I - C - CH2 - CH2 - CH3
2
Haloalkanes or alkyl halides
Example:
Parent chain
Side chains
CH2 - CH2 - CH2 - CH2 - CH3
CH2 - CH2 - CH2 - CH3
5
9 106 7 8
4 3 1
I - C - CH2 - CH2 - CH3
2
Haloalkanes or alkyl halides
Example:
Parent chain
decane
Side chains
CH2 - CH2 - CH2 - CH2 - CH3
CH2 - CH2 - CH2 - CH3
5
9 106 7 8
4 3 1
I - C - CH2 - CH2 - CH3
2
Haloalkanes or alkyl halidesExample:
Parent chain
decane
Side chainsPropyl groupIodo group
CH2 - CH2 - CH2 - CH2 - CH3
CH2 - CH2 - CH2 - CH3
5
9 106 7 8
4 3 1
I - C - CH2 - CH2 - CH3
2
Haloalkanes or alkyl halidesExample:
Parent chain
decane
Side chainsPropyl groupIodo group
CH2 - CH2 - CH2 - CH2 - CH3
CH2 - CH2 - CH2 - CH3
5
9 106 7 8
4 3 1
I - C - CH2 - CH2 - CH3
2
5-iodo-5-propyldecane
Cycloalkanes
C C
C C
H H
HH
H
H
H
H
C C
C C
C
C C
CC
HH
H
H
H H
H
H
HH
Carbon skeleton
Structural Formula
Geometric Formula
MolecularFormula
CYCLOPROPANE For cyclic compounds, each corner represents a
carbon atom and hydrogens are not shown. C3H6
CYCLOBUTANE
C4H8
CYCLOPENTANE
C5H10
Nomenclature of cycloalkanes
Example: Name the following cycloalkane.
CH3
CH2CH3
CH31
2
4
Ethyl comes before methyl alphabetically
Nomenclature of cycloalkanes
Example: Name the following cycloalkane.
CH3
CH2CH3
CH31
2
4
Ethyl comes before methyl alphabetically
The numbering results in the lowest branch locations (1,2,4) rather than 1,3,4)
Nomenclature of cycloalkanes
Example: Name the following cycloalkane.
CH3
CH2CH3
CH31
2
4
Ethyl comes before methyl alphabetically
The numbering results in the lowest branch locations (1,2,4) rather than 1,3,4)
Nomenclature of cycloalkanes
Example: Name the following cycloalkane.
CH3
CH2CH3
CH31
2
4
4-ethyl-1,2-dimethylcyclohexane
Ethyl comes before methyl alphabetically
The numbering results in the lowest branch locations (1,2,4) rather than 1,3,4)
Nomenclature of Alkenes
CH - C - CH - CH3
CH
23CH -
2
22 3 4
1 Find the longest continuous carbon chain that contains the double bond
Example: Name the following alkene.
Nomenclature of Alkenes
CH - C - CH - CH3
CH
23CH -
2
22 3 4
1 Find the longest continuous carbon chain that contains the double bond
An ethyl group is attached to carbon 2.
Example: Name the following alkene.
Nomenclature of Alkenes
CH - C - CH - CH3
CH
23CH -
2
22 3 4
1 Find the longest continuous carbon chain that contains the double bond
An ethyl group is attached to carbon 2.
2-ethyl-1-butene
Example: Name the following alkene.
Cis-trans Isomerism of Alkenes
CH3
Br
H
Br
CH3
Br
Br
H
Br Br
Br's are on opposite side of double bond
Br's are on same side of double bond
CH3 - C = CH
trans-1,2-dibromopropenecis -1,2-dibromopropene
C = CC = C
Cis-trans Isomerism of Alkenes
No cis-trans isomers occur if either carbon atom in the double bond is attached to identical groups or atoms.
H
H
Br
CH3
no cis-trans isomers are possible because twoof the same atom (i.e., H's) are present on thesame indicated carbon.
C = C
Nomenclature of Cycloalkenes
1
CH3
CH3
CH3
2
34
The double bond must be in positions 1 and 2.
Example: Name the following cycloalkene.
Nomenclature of Cycloalkenes
1
CH3
CH3
CH3
2
34
The double bond must be in positions 1 and 2.
The numbering is placed so that the branches have the lowest possible numbers.
Example: Name the following cycloalkene.
Nomenclature of Cycloalkenes
1
CH3
CH3
CH3
2
34
The double bond must be in positions 1 and 2.
The numbering is placed so that the branches have the lowest possible numbers.
3,3,4-trimethylcyclopentene
Example: Name the following cycloalkene.
General Reaction for Alkenes
A B
The double bond is brokenand atoms A and B are added,
one to each carbon.C - C+ A - BC = C
Hydrogenation
Halogenation
Hydrohalogenation
Hydration
Hydrohalogenation of AlkenesAddition of hydrohalogen, such as:
HF, HCl, HBr and HI
H X
C = C + H-X C - C
Hydrohalogenation of Alkenes
CH3 H
H H
CH3 H
H H
Cl HH was added to C
having the most H's
C - C+ H-Cl
This carbon has 2 HThis carbon has only 1 H
C = C
Markovnikov's Rule states that the H is added to the carbon that has the most H's
Hydration of Alkenes
Markovnikov addition
CH3CH3
OHH+
+ H-OH
This carbon has 1 H
This carbon has no H
H
CH3OH
Nomenclature of Alkynes
The rules are basically the same as those for naming alkenes; however, the parent chain name is changed to end in "yne".
C C - CH CH3 -
CH3
- CH2 - CH
CH3
2
7
3 4 5 621
Nomenclature of Alkynes
Find the longest chain that contains the triple bond.
heptyne
C C - CH CH3 -
CH3
- CH2 - CH
CH3
2
7
3 4 5 621
Nomenclature of Alkynes
Number from the end of the chain that gives the triple bond the lower numbers.
C C - CH CH3 -
CH3
- CH2 - CH
CH3
2
7
3 4 5 621
Nomenclature of Alkynes
Then identify and name the side chains (branches)
methyl group
C C - CH CH3 -
CH3
- CH2 - CH
CH3
2
7
3 4 5 621
Aromatic Hydrocarbons
Most aromatic hydrocarbons are derivatives of benzene
Examples:
ClCl
Cl
Br
I
CH2-CH3
1-ethyl-4-iodobenzenep-ethyliodobenzene
1-bromo-3-chlorobenzenem-bromochlorobenzene
1,2-dichlorobenzeneo-dichlorobenzene
Aromatic Hydrocarbons
Most aromatic hydrocarbons are derivatives of benzene
Examples:
ClCl
Cl
Br
I
CH2-CH3
1-ethyl-4-iodobenzenep-ethyliodobenzene
1-bromo-3-chlorobenzenem-bromochlorobenzene
1,2-dichlorobenzeneo-dichlorobenzene