Transcript CHAPTER 11 BONDING AND MOLECULAR STRUCTURE:

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 2 s bonds.
• With sp2 hybridization there is one (1)
p bond and 3 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.
Alkane
Organic chemistry is the study of
Alkene
compounds containing carbon.
Alkyne
The goal of studying Organic
Alkyl halide chemistry is the making of
carbon-carbon bonds, C-X, C-O, C-N,
Aromatic
and C-S bonds to make new molecules
Alcohol
Aldehyde
Ketone
Carboxylic Acid
Ester
Inorganic molecules like CO, and
Amine
CO3-2 are not considered organic
Amide
molecules.
1. Alkanes
Figure 11.4
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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
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
H
CH3
Me
H
e t hyl
H
H
H
C
C
H
H
H
CH2C H3
Et
Nomenclature
Haloalkane
26
Alcohol
27
Ether
28
Amine
29
Aldehyde
30
Ketone
31
Carboxylic acid
32
Ester
33
Amide
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
If two different substituents are attached to the
carbon chain, name them in alphabetical order.
CH CH
2
C
1
C
2
CH
3
C
3
3
C
4
C
5
Numbering starts at
the side with the
heavier functional
Group
2- ethyl-4-methylpentane
CH 3
C
1
C
2
CH2CH3
C
3
C
4
Numbering starts closest 4-ethyl-2-methylhexane
to 1st functional group
C
5
C
6
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
Practice
methylcyclopentane
1-ethyl-2-methylcyclopentane
Practice
Br
C
C
Cl
C
C
C
2-bromo-4-chloropropane
Br
C
C
Br
C
C
Br
2,2,4-tribromopropane
C
Draw the following
•
•
•
•
•
•
Butane
Butene
Butyne
Butanol
Butanal
Butanone
•
•
•
•
•
•
Dibutyl ether
Butanoic acid
Butyl butanoate
Butyl amine
Dibutyl amine
Tributyl amine
Structure, Bonding, and Isomerism
• Alkenes have the possibility of cis- transisomerism since the pi bond does not
permit rotation.
• Illustration: the three isomers of butene
(isobutene is actually a propene).
• The position of the atoms changes the
physical properties listed.
• If a molecule has two double bonds
between carbon atoms, it is called a
diene.
Double and Triple Bonds
Double and Triple Bonds
trans-2-butene
Double and Triple Bonds
trans-2-pentene
1. Draw a cis, trans-2,4-heptene
2. Name the following
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.
Markovnikov Addition
Br
CH3CH2CH2CH2CH2
C
CH
HBr
ethanol
?
CH3CH2CH2CH2CH2 C
H
HBr
CH
ethanol
Br
?
CH3 CH2CH2CH2CH2 C
Br
H
CH
H
The hydrogen adds to the carbon with the most hydrogen
ALKENE to ALKANE
ALKENES: Addition
ALKENES: Elimination
AROMATIC COMPOUNDS
Naphthalene
Benzene
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.
Substitution reactions with aromatic compounds,
not addition
CnH2n+2
CnH2n
CH3
CH2
CH3
CH2
+ Br2
+ Br2
no react ion
H
Br
Br
C
C
H
H
H
Br
CnHn
+ Br2
+ HBr
Naming Aromatic Compounds
OH
CH3
CH3
CH3
phenol
toluene
napthalene
o-xylene
anthracene
X
ortho -- o
meta -- m
para -- p
CH3
CH3
CH3
CH3
p-xylene
o-xylene
CH3
m-xylene
CH3
Benzene Reactions
halogenation
Br
+ Br2
+ HBr
Benzene Reactions
nitration
NO2
+ HNO3 (conc)
H2SO4 (conc)
+ H3O+
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
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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.
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Addition to Ethylene or
Elimination by ALCOHOLS
H2C
CH2 + H2O
H3PO4
CH3CH2OH
H2SO4
Forward is an oxidation, the reverse a reduction.
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
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
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
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Suggest a method for making
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.
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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
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Esters
• In basic solution, esters are hydrolyzed
to the alcohol and the salt of the
carboxylic acids
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.
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Alkyl halides
• RX react with magnesium metal to form
a Grignard reagent.
• This reagent reacts with aldehydes and
ketones to form alcohols and with
carbondioxide to form carboxylic acids.
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
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.
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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
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