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CHAPTER 11
BONDING AND MOLECULAR
STRUCTURE:
ORGANIC CHEMISTRY
All bold numbered problems.
Overview
• Organic chemistry is the study of
compounds containing carbon combined
with other non-metals.
• Bonding plays a critical role in
understanding the reactivity of these
compounds.
• These compounds are referred to as
hydrocarbons since they are primarily
hydrogen and carbon.
Overview
Overview
• Carbon uses sp3, sp2, and sp
hybridization in forming the four
bonds per carbon atom common to
almost all carbon compounds.
• With sp hybridization, there are two
(2) p bonds and 1 s bonds.
• With sp2 hybridization there is one (1)
p bond and 1 s bonds.
Why Carbon
sp3, sp2, and sp hybridization
Allotropes of Carbon
Carbon only
(no other atom) compounds
importance
FUNCTIONAL GROUPS
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
Alkane
Alkene
Organic chemistry is the study of
Alkyne
compounds containing carbon.
The goal of studying Organic
Alkyl halide
chemistry is the making of
Aromatic
carbon-carbon bonds, C-X, C-O, C-N,
and C-S bonds to make new molecules
Alcohol
Ethers
Aldehyde
Ketone
Carboxylic Acid
Inorganic molecules like CO, and
Ester
-2 are not considered organic
CO
3
Amine
molecules.
Amide
1. Alkanes
Figure 11.4
10
Structural Formula
BP
(C)
MP
(C)
1
CH4
-161
-183
ethane
2
CH3CH3
-88
-172
propane
3
CH3CH2CH3
-45
-187
butane
4
CH3CH2CH2CH3
-.5
-138
pentane
5
CH3CH2CH2CH2CH3
36
-130
hexane
6
CH3CH2CH2CH2CH2CH3
69
-95
heptane
7
CH3CH2CH2CH2CH2CH2CH3
98
-90
octane
8
CH3CH2CH2CH2CH2CH2CH2CH3
125
-57
nonane
9
CH3CH2CH2CH2CH2CH2CH2CH2CH3
151
-54
decane
10
CH3CH2CH2CH2CH2CH2CH2CH2CH2CH
175
-30
Name
# of
C's
methane
3
Alkanes
12
Abbreviated, common method to write organic cmpds
Name
methane
Structural Formula
C
CH4
ethane
CH3CH3
propane
CH3CH2CH3
butane
CH3CH2CH2CH3
pentane
CH3CH2CH2CH2CH3
ALKANES
• There are frequently many
hydrocarbons with the same formula.
These are called structural isomers.
C5H12 has three isomers
C10H22 has 75 isomers
C20H42 has 366,319 isomers
Isomers of
Butane-5
Carbon
chains
C6H14 has five isomers,
draw them.
Cycloalkanes
• Cycloalkanes are ring structures and
have the general formula CnH2n.
• Do not confuse these compounds
with the alkenes which have the same
general formula.
2. ALKENE AND 3. ALKYNE
• These compounds are referred to as
unsaturated.
• Alkenes contain one or more double
bonds and alkynes contain one or more
triple bonds.
Saturated –vs- Unsaturated
Saturated Hydrocarbon C15H32
Unsaturated Hydrocarbon
Contains either double and/or triple bonds
Notice how the chains do not line up
21
Single bonds only Fats
Double bonds Fats
ALKENES
ALKYNE
Physical properties
change
Isomers have different physical as well as
different chemical properties
Nomenclature
• Organic Functional Groups and Nomenclature
• Substituents - saturated carbon substituents are called
alkyl groups and are named based on the naming of the
normal alkanes.
H
methy l
C
H
CH3
Me
H
e t hyl
H
H
C
C
H
H
H
CH2C H3
Et
Nomenclature
Haloalkane
27
Alcohol
28
Ether
CH3
CH2
O
CH2
CH3
29
Amine
30
Aldehyde
O
CH3
C
H
31
Ketone
32
Carboxylic acid
O
CH3
C
OH
33
Ester
O
CH3
C
O
CH3
34
Amide
35
Draw the following
•
•
•
•
•
•
Butane
Butene
Butyne
Butanol
Butanal
Butanone
•
•
•
•
•
•
Dibutyl ether
Butanoic acid
Ethyl butanoate
Butyl amine
Dibutyl amine
Tributyl amine
Common Alcohol Names
What is the name of this Alcohol?
alcohol
methyl
Methanol
The main chain is numbered such that
the first substituent encountered along
the chain receives the lowest possible
number.
CH 3
C
1
C
2
C
3
C
4
C
5
2-methylpentane
CH 3
C
5
C
4
NOT
C
3
4 -m ethylpent ane
C
2
C
1
If two or more identical substituents are attached to
the same C-chain , prefixes di-, tri-, tetra-, etc. are
used with numbers to indicate position.
CH 3
C
1
C
2
CH3
C
3
C
4
C
5
2 ,4- dimethylpent ane
CH3
C
1
2
C
C
3
C
4
C
5
CH3
2, 2-dimethylpentane
40
Quiz Chapter 4 Section 3
Provide the IUPAC names of the alkanes below.
CH3
CH3CH2CHCH2CHCH3
CH2CH3
3,5-dimethylheptane
(CH3)2CHCH2CH(CH3)2
2,4-dimethylpentane
If two different substituent's are
attached to the carbon chain, name
them in alphabetical order.
CH CH
2
C
1
C
2
C
3
CH
3
C
4
C
5
3
C
6
C
7
3-ethyl, 5-methylheptane
Numbering starts at
the side with the
heavier functional
Group
Numbering starts closest
to 1st functional group
Practice
C
C
C
C
C
C
C
C
C
3
C
C
2
C
4
C
5
C
6
C
1
3-ethylhexane
C
–Nomenclature of Branched Alkyl Chains
» Two alkyl groups can be derived from propane
43
–Nomenclature of Branched Alkyl Chains
» Four groups can be derived from the butane
isomers
44
44
45
Examples
46
• Classification of Hydrogen Atoms
» Hydrogens take their classification from the
carbon they are attached to
46
47
Quiz Chapter 4 Section 3D
Name the alkane below and identify as 1o, 2o and 3o , all groups of
equivalent H.
1o
2o
CH3CH2CHCH2CH3
CH3
1o
3-methylpentane
3o
48
–Nomenclature of Alkyl Halides
» In common nomenclature the simple
haloalkanes are named as
alkyl halides
• Common nomenclature of simple alkyl halides is accepted by IUPAC
and still used
48
Practice
Br
C
C
Cl
C
C
C
2-bromo-4-chloropentane
Br
C
C
Br
C
C
Br
2,2,4-tribromopentane
C
50
– IUPAC Substitutive Nomenclature
» An IUPAC name may have up to 4 features: locants,
prefixes, parent compound and suffixes
» Numbering generally starts from the end of the chain
which is closest to the group named in the suffix
– IUPAC Nomenclature of Alcohols
» Select the longest chain containing the hydroxyl and
change the suffix name of the corresponding parent
alkane from -ane to -ol
» Number the parent to give the hydroxyl the lowest
possible number
» The other substituents take their locations accordingly
50
Common Names of simple alcohols are still
often used and are approved by IUPAC
51
52
Common Names of Alcohols
Alkyl group names are approved by IUPAC for naming alcohols:
"alkyl group + alcohol."
CH3CH2OH
Ethanol
CH3
CH3CCH2OH
CH3
OH
CH3CHCH3
2 propanol
or
isopropanol
Neopentylol
or
2,2-Dimethyl-1-propanol
C
53
» Alcohols with two hydroxyls are called diols
in IUPAC nomenclature and glycols in
common nomenclature
53
Name the following compound.
CH3CHClCH2CHOH
CH3
4-chloro-2-pentanol
Draw
54
55
Nomenclature of Cycloalkanes
Cyclic alkanes are named with the "cyclo" prefix followed by the
alkane name indicating the number of carbon atoms in the ring.
CH2
CH2 CH2
cyclopropane
CH2 CH2
CH2 CH2
cyclobutan e
56
• Nomenclature of Cycloalkanes
–The prefix cyclo- is added to the name of the
alkane with the same number of carbons
• When one substituent is present it is assumed to be at
position one and is not numbered
• When two alkyl substituents are present the one with
alphabetical priority is given position 1
• Numbering continues to give the other substituent the
lowest number
• Hydroxyl has higher priority than alkyl and is given
position 1
• If a long chain is attached to a ring with fewer carbons,
the cycloalkane is considered the substituent
57
Substituted Cycloalkanes
The name of a substitutent is added as a prefix to the cycloalkane name.
Alkyl group names are used for simple alkyl group substituents.
When there are two or more substituents, the positions around the ring
are numbered beginning with the substituent first in the alphabet.
CH2CH3
Cl
CH3
CH3
CH3
ethylcyclohexane
1,3-dimethylcyclohexane
1-chloro-2-methylcyclopentane
3
The cycloalkane also
can be named as a
substituent on a long
chain, which is
sometimes more
convenient.
2
1
CH2CH2CH2OH
3-cyclohexyl-1-propanol
58
Practice
methylcyclopentane
1-ethyl-2-methylcyclopentane
Structure, Bonding, and Isomerism
• Alkenes have the possibility of cis- transisomerism since the pi bond does not
permit rotation.
• If a molecule has two double bonds
between carbon atoms, it is called a
“diene.”
Double and Triple Bonds
61
Name the following
Double and Triple Bonds
trans-2-butene
Double and Triple Bonds
trans-2-pentene
Draw a
cis, trans-2,4-heptatriene
cis,trans,trans,cis-2,4,6,8-decatetraene
65
AROMATIC COMPOUNDS
Naphthalene
Benzene
66
AROMATIC COMPOUND
• See your text for physical properties of
these compounds.
• Aromatics like benzene have sp2
hybridization with delocalized pi electrons.
The delocalized p bonding is the key to
these compounds.
• They do not undergo addition reactions
like alkenes and alkynes, but rather react
by way of substitution.
67
Substitution reactions with aromatic compounds,
not addition
CH3
CH2
CH3
CH2
+ Br
+ Br
No Reaction
H
Br
Br
C
C
H
H
H
Br
+ Br
+ HBr
68
Naming Aromatic Compounds
OH
CH3
CH3
CH3
Phenol
napthalene
Toluene
o-Xylene
anthracene
69
X
ortho -- o
meta -- m
para -- p
CH3
CH3
CH3
CH3
CH3
o-Xylene
m-Xylene
CH3
p-Xylene
70
Synthesis: substitution or
elimination
The following are all substitution reaction. Replacing one
atom with another.
• Alkyl halides (3)
• Reaction with aromatic compounds (3)
• Making an alcohol (1)
• From Alcohols make aldehydes, ketones, and carboxylic
acids.
The only other type of synthesis is removing an atom, this
is called elimination.
Preparation of Alkenes
and Alkynes
• Acetylene aka ethyne, from calcium carbide, CaC2
• Steam cracking for the formation of ethylene,
ethene, from ethane.
Addition Reactions
• Symmetrical addition is simple, but asymmetrical
addition follows Markovnikov's rule: the hydrogen
adds to the carbon with the most hydrogen.
For alkynes, the addition is always two mole to one
mole of alkyne, the product being a substituted
alkane. If hydrogen gas is added, the process is
called hydrogenation.
72
Addition of Hydrogen Halides to Alkenes: Markovnikov's Rule
Hydrogen halides (HCl, HBr, HI) add to alkenes:
X = Cl, Br, I
+ H-X
A
B
These reactions may be carried out by adding HX to a solvent such as
acetic acid or dichloromethane in the presence of the alkene, or by
bubbling gaseous HX into a solution of the alkene.
The reactivity order of HX in these additions is:
HI > HBr > HCl
The reactivity of HCl is very low except
with highly substituted alkenes.
73
Regiochemistry of the Addition Reaction
Regiochemistry means the specific carbons of the alkene to which the
H and X attach. In unsymmetrical alkenes, there are two possible
regiochemistries:
CH2=CHCH3 + HBr
propene
Br
CH3CHCH3
2-bromopropane
Br
+ HBr
2-methylpropene
2-bromo-2-methylpropane
CH3CH2CH2Br
1-bromopropane
very little formed
CH3CHCH2Br
CH3
1-bromo-2-methylpropane
very little formed
74
Markovnikov's Rule
Vladimir Markovnikov (University of Kazan) in 1869:
"The hydrogen of the acid attaches to the carbon that already
holds the greater number of hydrogens."
This prediction is called
"Markovnikov's Rule."
CH2=CH-CH3
CH2-CH-CH3
H
H
Br
Br
Markovnikov addition product
Addition reactions that follow this rule are called
Markovnikov Additions.
Markovnikov Addition
CH3CH2CH2
C
CH
1 mol HBr
ethanol
Br
Br
1 mol HBr
CH3CH2CH2
C
CH3CH2CH2
CH
ethanol
CH3CH2CH2
Br
Br
C
CH
Br
Br
C
CH
Br
Br
The hydrogen adds to the carbon with the most hydrogen
ALKENES: Addition
77
Examples of the Halogenation Reaction
Chlorination
CH3CH2CH=CH2 + Cl2
1-butene
CH3CH2CHClCH2Cl
- 9o C
1,2-dichlorobutane
Bromination
+ Br2
- 5o C
+
CCl4/ethanol
cyclopentene
Br
Br
Br
trans-1,2-dibromocyclope
(Racemic Form)
ALKENE to ALKANE
ALKENES: Elimination
Benzene Reactions
halogenation
Br
+ Br2
+ HBr
Benzene Reactions
nitration
NO2
+ HNO3 (conc)
H2SO4 (conc)
Benzene Reactions
alkylation
CH2CH2CH2CH3
CH3CH2CH2CH2Cl
AlCl3
ALCOHOLS
ALCOHOLS
Naming Alcohols
• The alkane name is modified by dropping the e
and adding ol.
CH3CH2OH is ethanol
• If three OH groups are present, the molecule is
called a triol.
CH3C(OH)3 is ethantriol
Primary, secondary, and tertiary alcohols
H
C
R
R
R
OH
H
primary or 1°
R
C
OH
H
secondary or 2°
R
C
OH
R
tertiary or 3°
What type of alcohol’s are these?
1°, 2°, 3°?
Metalation of Alcohols
Sodium metal reacts with an alcohol to produce
hydrogen gas and the sodium alkoxide, refered to
as a metalation, since the oxygen is still attached.
CH3CH2OH + NaH
OH
CH3CH2O-Na+ + H2
O-Na+
+ NaOH
+ H2O
89
Chemistry of Alcohols
1. Alcohols can go through substitution,
and elimination reactions
Which means Alcohols are either
oxidized or reduced
Formation of ALCOHOLS
addition reaction to an alkene
H2C
CH2 + H2O
H3PO4
CH3CH2OH
Could also be called an oxidation reaction
because we’re adding oxygen to the carbon
Substitution
• An alcohol reacts with HX to produce the
alkylhalide and water, where X is Cl, Br, I
• CH3CH2OH + HCl
CH3CH2Cl + H2O
Elimination
• In the presence of concentrated sulfuric acid and
heat an alcohol will eliminate water and form an
alkene; the reverse of how alcohols are formed.
92
Suggest a method for making
Starting with 1 butene make 2-bromo butane
Br
CH3 CH2
CH
CH2
HBr
CH3 CH2
ethanol
CH
CH3
Markovnikov
Starting with 1 butene make 1-bromo butane
CH3 CH2
CH3 CH2
CH
CH2
H3PO4
CH2 CH2 OH
CH3 CH2
HBr
ethanol
CH2 CH2 OH
CH3 CH2
CH2 CH2 Br
93
Addition to Ethylene or
Elimination by ALCOHOLS
H2C
CH2 + H2O
H3PO4
CH3CH2OH
H2SO4
Forward is an oxidation, the reverse a reduction.
94
• Oxidation of Alcohols
–Oxidation of Primary Alcohols to
Aldehydes
» A primary alcohol can be oxidized to an
aldehyde or a carboxylic acid
• The oxidation is difficult to stop at the aldehyde stage and usually proceeds
to the carboxylic acid
» A reagent which stops the oxidation at the
aldehyde stage is pyridinium chlorochromate
(PCC)
• PCC is made from chromium trioxide under acidic conditions
• It is used in organic solvents such as methylene chloride (CH2Cl2)
95
96
Alcohols can be oxidized to
carboxylic acids or ketones
1. primary alcohols to aldehydes with mild
Oxidizing agents
O
PCC
CH3CH2
PCC =
C
OH
H3C
N+
H
CrO3Cl-
Pryidinium chlorochromate
H
Alcohols can be oxidized directly to
carboxylic acids or ketones
1. primary alcohols directly to acids by STRONG
oxidizing agents
O
CH3CH2
OH
CrO3, H+
C
H3C
Notice lose of 2H+
OH
Alcohols can be oxidized to
carboxylic acids or ketones
2. secondary alcohols to ketones
O
OH
PCC
CH
CH3
CH3
2-propanol
C
H3C
CH3
propanone
Notice lose of 2H+
Tertiary alcohols
No reaction
OH
PCC, or CrCl3
CH3
C
CH3
no reaction
CH3
Why?
CARBONYLCOMPOUNDS
The carbonyl group is a carbon atom double
bonded to an oxygen atom, and is found in
aldehydes, ketones, carboxylic acids, and esters.
O
C
102
NaBH4 or LiAlH4
103
CARBONYL COMPOUNDS
CARBONYL COMPOUNDS
• The aldehyde has at least one hydrogen
atom bonded the carbonyl carbon.
• The ketone has two carbon atoms bonded
to the carbonyl carbon.
• The carboxylic acid has an OH bonded to
the carbonyl carbon.
• The ester is a combination of an alcohol
and a carboxylic acid.
• aldehyde, RCOH;
carboxylic acid, RCOOH;
ketone, RCOR';
ester, RCOOR'.
CARBONYL COMPOUNDS
• Carboxylic acids can be formed by oxidizing
primary alcohols or aldehydes.
• Reducing aldehydes and acids with NaBH4 or
LiAlH4 produces a primary alcohol.
• Reduction of a ketone produces a secondary
alcohol.
107
–The Use of Lithium Reagents
»Organolithium reagents react
similarly to Grignard reagents
• Organolithium reagents tend to be
more reactive
108
The Use of Sodium Alkynides
»Sodium alkynides react with
carbonyl compounds such as
aldehydes and ketones to form
new carbon-carbon bonds
109
Esters
• Form from carboxylic acids and alcohols when
heated with sulfuric acid. They are named from
the alcohol and the acid with an ate ending
CH3CH2OH + CH3COOH
CH3COOCH2CH3
110
Esters
Synthesis of Esters
Direct Esterification of Carboxylic Acids
Carboxylic acids and alcohols react in the presence of a small
amount of strong acid to give esters.
COOH
COOCH3
+ CH3OH
Benzoic acid
Methanol
H+
+ H2O
Methyl benzoate
Esterifications are acid-catalyzed equilibrium reactions. Catalytic
amounts of concentrated sulfuric acid or hydrochloric acid are used.
Usually a large excess of the alcohol (10- or 15-fold) is used to drive the
equilibrium to the product side. Product formation can also be
promoted by removing the water as it is formed.
111
This mechanism for esterification is consistent with the
incorporation of the isotopic label:
H+
O
C6H5COCH3 + H2O
=
=
O
C6H5COH + CH3OH
A Mechanism for Acid-Catalyzed Hydrolysis of Esters
Since every step is reversible, the reverse of the esterification
scheme is the mechanism for the acid-catalyzed hydrolysis of
esters.
H+
+ H2O
O
C6H5COH + CH3OH
=
=
O
C6H5COCH3
The direction of the reaction is controlled by the relative
concentrations of water versus alcohol.
112
Transesterification
This is a process whereby the ester of one alcohol may be
converted into the ester of a second alcohol by the equilibrium:
H+
O
RCOR'' + R'OH
=
=
O
RCOR' + R''OH
An example
=
O
CH2=CHCOCH3 + CH3CH2CH2CH2OH
Methyl acrylate
H+
Butyl alcohol
=
O
CH2=CHCOCH2CH2CH2CH3 + CH3OH
Butyl acrylate
Methyl alcohol
The equilibrium is shifted to the product side by using an excess of butyl
alcohol and/or distilling out the lower boiling methanol from the
reaction mixture.
Alkyl halides RX
• React to form alcohols in water using a
strong base like NaOH, substitution
reaction.
• In an alcohol solvent, the same reactants
form an alkene, elimination reaction.
CH3 CH2
CH3 CH2
CH2 CH2 Br
CH2 CH2 OH
NaOH
Heat
CH3 CH2
CH3 CH2
CH2 CH2 OH
CH
CH2
Ethers
R-O-R’
(Additional material)
• Ethers, R-O-R', can be formed from the
reaction of alcohols when heated in the
presence of concentrated sulfuric acid.
• See Lab IVCX 15
2 CH3 CH2
CH2 CH2 OH
sulfuric
CH3 CH2
CH2 CH2 O
CH2 CH2
CH2 CH3
11.6 FATS AND OILS
• Fats and oils are esters of glycerol
1, 2, 3-propanetriol
• The R group of the triester is a long chain fatty
acid.
BOOM!
FATS AND OILS
• Some fats are saturated, some
unsaturated, and some are
polyunsaturated.
• When the triester is hydrolyzed with strong
base, the sodium or potassium salt forms
and is called a soap.
–The process is also called saponfication.
Single bonds only Fats
Double bonds Fats
AMINES AND AMIDES
• React as bases and have bad smells
• React with carboxylic acids to form amides which are similar
in structure to esters.
AMINES
AMIDES
Polymers
S
U
L
F
U
R
11.7 SYNTHETIC POLYMERS
• Polymers are formed from combinations of
monomers.
• They can be classified many ways.
–Thermoplastics can be heated and
reformed again and again.
–Thermosetting plastics are heated and
formed, but cannot be heated and
reformed because of their high degree of
cross-linking.
11.7 SYNTHETIC POLYMERS
• Another classification system for polymers is
based on their intended use:
- plastics
- fibers
- Elastomers
- coatings
- adhesives
• Polymers can also be classified by the way
they form:
–addition polymers
–condensation polymers
Addition Polymers
• The monomers for these polymers all
have a double bond.
• If an appropriate initiator is added,
these monomers can add to the chain
one at a time by breaking the double
bond.
• This process is called chain growth
polymerization.
• Copolymers are formed from a mixture
of monomers.
127
Addition: Free Radical
Polyethylene: Addition
CH2
CH2
CH2
CH2
n
Polypropylene
CH3
CH
CH3
CH2
CH
CH2
n
(a) Linear, straight
Polyethylene
Branching
Bridging, crosslink
Teflon
CF2
CF2
CF2
CF2
n
What would the following addition polymers look like
O
C
O
Cl
CH
CH2
for PVC
CH2
CH3
CH
methyl methacrylate
for Lucite, Plexiglass
CH
CH2
stryene
for styrofoam
PETE (polyethylene terephthalate), HDPE (highdensity polyethylene), LDPE (low-density
polyethylene), PP (polypropylene), CLPE (cross-linked
polyethylene, V (vinyl) or PVC, also RLDPE (resin mix,
already recycled. The # is another way of identifying
that polymer.
Condensation Polymers
• These polymers are usually
copolymers.
• One monomer is a dicarboxylic acid
and the other monomer is either a
dialcohol or a diamine.
• These polymers are named as
polyesters or polyamides.
Nylon 66
Polyamide
Chains
Monomers
Polymer
137