C-H bonds in methane
Figure 22.2: (a) Lewis stucture of ethane (C2H6). (b)
molecular structure of ethane
HYBRIDIZATION?
Name calling
H
H C H
H
methane
Name calling
H H
H C C H
H H
ethane
Name calling
H H H
H C C C H
H H H
propane
Name calling
H H H H
H C C C C H
H H H H
butane
Name calling
H H H H H
H C C C C C H
H H H H H
pentane
Name calling
H H H H H H
H C C C C C C H
H H H H H H
hexane
Name calling
H H H H H H H
H C C C C C C C H
H H H H H H H
heptane
Name calling
H H H H H H H H
H C C C C C C C C H
H H H H H H H H
octane
Name calling
•
•
•
•
•
•
•
•
CH4
C2H6
C3H8
C4H10
C5H12
C6H14
C7H16
C8H18
methane
ethane
propane
butane
pentane
hexane
heptane
octane
Figure 22.3: Structures of (a) propane
(b) butane
H H H
H C C C H
H H H
H
H C
H
HYBRIDIZATION?
H
C
H
H
C
H
H
C H
H
Figure 22.3: Structures of (a) propane
(b) butane
H H H
H C C C H
H H H
H
H C
H
H
C
H
H
C
H
H
C H
H
Figure 22.3: Structures of (a) propane
(b) butane
C
C
C
C
C
C
C
Figure 22.3: Structures of (a) propane
(b) butane
C
C
C
C
CH
CH3
CH3
CH
H H H H
H C C C C H
H
H
Reactions of Alkanes
Combustion
alkane + O2
CO2 + H2O + heat
Learning Check Alk3
Complete and balance the reaction for the
complete combustion of C7H16
Solution Alk3
Step 1
C7H16 + O2
CO2 + H2O
Step 2
C7H16 + O2
7 CO2 + 8 H2O
Step 3
C7H16 + 11 O2
7 CO2 + 8 H2O
Combustion In the Cell
Metabolic oxidation is combustion
C6H12 O6 + 6O2
6CO2 + 6H2O + heat
glucose
• How does this reaction occur in living
organisms?
Aerobic Oxidation Occurs in a
Mitochondrion Located within a Cell
Branched Alkanes
Structural Formulas
Structural Isomers
Alkyl Groups
Branches on carbon chains
H
H
H
C
H
H
H
H
C
C
H
H
methane
H
ethane
Alkyl Groups
Branches on carbon chains
H
H
H
C
H
H
H
C
C
H
H
CH3
methyl
CH3CH2
ethyl
Branched Alkanes
CH3
CH3CHCH3
methyl groups
CH3
CH3
CH3CHCH2CHCH3
Naming Branched Alkanes
CH3
methyl branch
CH3CH2CH2CHCH2CH3
6
5
4
3
2
1
Count
Naming Branched Alkanes
CH3
methyl branch
CH3CH2CH2CHCH2CH3
6
5
4
3 2
1
Count
3-Methylhexane
on third C
CH3
six carbon chain
group
Naming Summary
1. Count the C’s in the longest chain
2. Name each attached group
3 Count the longest carbon chain to
give the first attached group the
smallest number
4. Name and locate each group
Learning Check Alk4
A.
CH3
CH3
CHCH2CH
CH3
B.
CH3
CH3
CH3
CH3CH2CHCH2CH
CH3
CH2CH3
Solution Alk4
A.
CH3
CH3
CH3CHCH2CHCH3
B.
CH3
2,4-dimethylpentane
CH3
CH3CH2CHCH2CHCH2CH3
CH3
3,3,5-trimethylheptane
Learning Check Alk5
Write a condensed structure for
A. 3,4-dimethylheptane
B.
2,2-dimethyloctane
Solution Alk5
A. 3,4-dimethylheptane
CH3
CH3CH2CHCHCH2CH2CH3
CH3
B. 2,2-dimethyloctane CH3
CH3CCH2CH2CH2CH2CH2CH3
CH3
Isomers
Same molecular formula
Same number and types of atoms
Different arrangement of atoms
Butane
structures
n-butane
methylpropane
Learning Check Alk6
Write 3 isomers of C5H12 and name each.
Solution Alk6
CH3CH2CH2CH2CH3
pentane or n-pentane
CH3
CH3CHCH2CH3
2-methylbutane
CH3
CH3CCH3
CH3
2,2-dimethylpropane
Cyclic
Alkanes
Cyclopropane
structure
Cyclohexane
structure
Figure 22.11: The structure of benzene
Naming Cycloalkanes with
Side Groups
Number of
side groups
Naming
One
Side group name goes in front
of the cycloalkane name.
Two
Number the ring in the
direction that gives
the lowest numbers
to the side groups.
Cycloalkanes with Side Groups
CH3
methylcyclopentane
CH3
CH3
1,2-dimethylcyclopentane
CH3
CH3
1,2,4-trimethylcyclohexane
CH3
Learning Check Alk8
Name the following cyclic alkanes
CH 3
CH 3
CH 3
CH 3
CH3
Solution Alk8
CH3
1,2-dimethylcyclobutane
CH3
CH3
methylcyclopentane
CH3
1,3-dimethylcyclohexane
CH3
Saturated and Unsaturated
Compounds
Saturated compounds (alkanes) have
the maximum number of hydrogen
atoms attached to each carbon atom
Unsaturated compounds have fewer
hydrogen atoms attached to the carbon
chain than alkanes
Unsaturated compounds contain double
or triple bonds
Alkenes
Carbon-carbon double bonds
Names end in -ene
H2C=CH2
ethene (ethylene)
H2C=CH-CH3 propene (propylene)
cyclohexene
Alkynes
Carbon-carbon triple bonds
Names end in -yne
HCCH
ethyne(acetylene)
HCC-CH3
propyne
Naming Alkenes and Alkynes
When the carbon chain has 4 or more C atoms,
number the chain to give the lowest number to the
double or triple bond.
1
2 3 4
CH2=CHCH2CH3
1-butene
CH3CH=CHCH3
2-butene

CH3C CCH3
2-butyne
Learning Check HA3
Write the IUPAC name for each of the following
unsaturated compounds:
A.
CH3CH2CCCH3
CH3
CH3
B.
CH3C=CHCH3
C.
Solutions HA3
Write the IUPAC name for each of the following
unsaturated compounds:
A.
CH3CH2CH=CHCH3
2-pentyne
CH3
CH3
B.
CH3C=CHCH3
2-methyl-2-butene
C.
3-methylcyclopentene
Calling names
• ALKANES
• ALKENES
• ALKYNES
• CYCLO• ALKYL-
Hydrogenation
Adds a hydrogen atom to each carbon atom of a
double bond
H H
+
H–C=C–H
H H
Ni
H–C–C–H
H H
H H
ethene
ethane
Products of Hydrogenation
Adding H2 to vegetable oils produces compounds
with higher melting points
Margarines
Soft margarines
Shortenings (solid)
Figure 22.11: The structure of benzene
Figure 22.12: Some selected substituted benzenes and
their names
Compounds containing aromatic rings
are often used in dyes, such as these for
sale in a market in Nepal
Source: Getty Images
Bonding in ethane
Bonding in ethylene
Bonding in acytylene
Cis and Trans Isomers
Double bond is fixed
Cis/trans Isomers are possible
CH3
CH3
CH = CH
cis
CH3
CH = CH
trans
CH3
Vision begins with a light induced cis-trans
isomerization reaction of retinal
isomers
• Structural – chain
butane
methyl propane
• Structural - position
2methylhexane
3methylhexane
• Structural – function
• Stereo - geometrical
• Stereo - optical
cis
trans
STEREO-ISOMERS
Non-Superimposable Mirror Images
COOH
H
HO
CH 3
COOH
HO
C
H
COOH
H
CH3
C
CH3
lactic acid
OH
Electromagnetic Radiation
(b)
Figure 20.13: Unpolarized light consists of waves vibrating
in many different planes
Figure 20.14: Rotation of the plane of
polarized light by an optically active substance.
Optical Isomer and Interaction with Light
Enatiomers rotate the plane of polarized light.
Dextrorotatory- “d” isomer
Complex which rotates plane of polarized light to the right.
Levorotatory- “l” isomer
Complex which rotates plane of polarized light to the left.
Chiral molecules are optically active because effect on light
Polarizing sun glasses reduce glare of polarized
reflections from surfaces