The document discusses organic chemistry, including why the field is important for understanding biological processes and medicine. It covers topics like the structure and bonding of carbon compounds, isomerism, functional groups, and reactions of alkanes. The presentation provides an overview of the key concepts and components of organic chemistry.
1. Organic Chemistry
Selected sections Ch 26 + Ch 11
The chemistry of life and living
things
The chemistry of carbon compounds
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Evolution of the field
1
2. Why is organic chemistry important?
• To understand how we interact with
– other organisms (food & nutrients, infections),
– our environment (aromas, pollutants),
– drugs, and
– ourselves (metabolism, growth, immunity,
cancer)
• To understand how things are made, what
they're made of, and how they react with
each other
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Why is organic chemistry important?
• Because it is central to:
Chemistry
Chemical Biology
Biochemistry
Biology
Engineering
Material sciences
Forensic Sciences
Medicine
• To get into graduate/medical/dental school!
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Medical Application: Molecular Imaging
18F-fluorodeoxyglucose
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2
3. Organic Chemistry Components
1) Structure: The connectivity and 3-D nature of
compounds
2) Theory: Structure and reactivity in terms of
atoms and the electrons that bind them together
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Components (continued)
3) Synthesis: How to design new molecules – and
then make them
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Organic Compounds
• Why is one element in the periodic table
given its own field?
– 98% of all known chemical substances are
organic
• Inorganic chemistry = the chemistry of
everything else
• Nearly all pharmaceuticals are organic in
nature
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3
5. Organic Compounds: Drugs
CH3 OH
CH3
CH3
HN
N
H
Stanozolol
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Organic Compounds: Industrial Chemicals
HN
Indigo dye
(blue jeans)
O
O
NH
CO2H
H
N
H 2N
O
Aspartame
OMe
O
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Organic Compounds: Natural Products
O
O
N
Cocaine
O
O
N
HO
Quinine
MeO
N
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5
6. Alkanes
Section 26-1, 26-2
Alkanes
• Hydrocarbons – the simplest organic
compounds (CnH2n+2)
• Saturated (use all bonding e− to make
single bonds)
• Methane (various representations):
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Ethane (C2H6)
6
7. Propane (C3H8)
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Drawing Organic Molecules
• Guideline 1: Draw molecules in a Zig-Zag
shape versus linear structures
vs
CH3CH2CH2CH2CH2CH3
• Guideline 2: You can assume there are Hatoms attached to carbon atoms in a ZigZag structure giving a valence of 4
OH
H
H
H
H H
H
OH
H
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Drawing molecules (continued)
• Guideline 3: For reactions, draw out the
functional groups in detail and include lone
pairs (electrons)
OH
O
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7
8. Advice and hints
• Be neat – messy structures lead to mistakes
• Count your carbon atoms!
• Count the substituents on carbon atoms
(including implied H atoms)
• In this course, there are never more than four
bonds to carbon
22
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Diagnostic iClicker Question
Which of the following wedge-and-dash drawings of
propane is incorrect?
(a)
HH
H
H
H
H
H
H
H
H
H
(d)
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H H
H
(c)
(b)
(e) don't know
H H
23
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PB
Diagnostic iClicker Question
Which of the following wedge-and-dash drawings of
propane is incorrect?
H H
H
H
H
H
(a)
H
(c)
H
HH
H
H H H
(b)
H
H
H
H H H
(d)
H
H
H
H
H
H
H
H
H
H
(e) don't know
H H
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8
9. JV
Diagnostic iClicker Question
Which of the following wedge-and-dash drawings of
propane is incorrect?
(a)
(c)
H
H
H
H
H
H
H
H
H
(d)
HH
H
H
H
H
H
H
H
H
H
H
H
H H
H
H
H
H
H
(b)
H
(e) don't know
H H
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HS
Diagnostic iClicker Question
Which of the following wedge-and-dash drawings of
propane is incorrect?
H
(a)
H
H
H
H
H
H
H
H
(b)
H
H
(c)
H H H
H
H
(d)
H H H
H
H
H
H
H
H
H
H
H
H
H
H
(e) don't know
H
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Fuels: Octane Number
Octane Number: used to indicate the resistance of a
motor fuel to “knock”
p. 1084
9
10. Fuels: Alcohols
Alcohols can also be used as fuels:
CH3OH(l) +
1.5O2(g)
CH3CH2OH(l) + 3O2(g)
CO2(g) +
2H2O(l) ∆Ho = -726 kJ mol-1
2CO2(g) +
3H2O(l) ∆Ho = -1367 kJ mol-1
∆H°(combustion) for
CH4, methane -891 kJ/mol
C2H6, ethane
-1560 kJ/mol
http://pubs.acs.org/cen/coverstory/85/8551cover.html
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Structural Diversity
Isomers, cycloalkanes
Concept Check: Skeletal/Structural Isomerism
Skeletal or structural isomers have:
- The same molecular formula but different
connectivity.
- Different physical properties.
Concept check:
Draw structural isomers of C5H12
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10
11. Concept Check: Solution
H H H H H
H C C C C C H
H H H H H
pentane
H
H C H
H
H H
H C C C C H
H H H H
H
H C H
H
H
H C C C H
H
H
H C H
H
2-methylbutane
2,2-dimethylpropane
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Conformations of alkanes
Newman Projections
Lower E
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Conformation versus configuration
• Conformation: arrangement of atoms in a molecule that
can be changed by simple rotation of single bonds,
without breaking any bonds.
• Configuration: the permanent geometry of a molecule
resulting from the spatial arrangement of its bonds.
– Must break bonds to change configuration.
versus
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11
12. Conformations of ‘disubstituted ethane’
H H
R'
R
H
H
Staggered
R
R
H
H
H
H
H
H
R
R'
R'
H
H
H
R'
H
H
H
Lowest E
34
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Eclipsed Conformations
Eclipsed
HR
H
H
H
R'
HR
R' R
H
H
H
H
H
R'
H
H
Highest E
• All eclipsed conformations have higher energy than all
staggered conformations.
35
Chem
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PH
Formative iClicker Question #1
Which conformation has the lowest (most
favourable) energy?
R
(a)
H
H
R R'
RH
H
H
(b)
R'
H
H
(c)
R
(d)
H
R'
H
H
H
H
H
H
R'
R
(e)
H
H
H
H
H
R'
H
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12
13. PB
Formative iClicker Question #1
Which conformation has the highest (least
favourable) energy?
R
R R'
RH
H
H
(a)
H
H
(b)
(c)
H
H
R'
R
(d)
H
H
R
R'
H
H
H
H
R'
R'
(e)
H
H
H
H
H
H
H
37
Chem
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JV
Formative iClicker Question #1
Which conformation has the highest (least
favourable) energy?
R
R'
H
(a)
RH
R
H
H
H
H
(b)
H
H
H
(c) H
H
H
R'
R'
R R'
(d) H
H
R
H
R'
(e)
H
H
H
H
H
38
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HS
Formative iClicker Question #1
Which conformation has the lowest (most
favourable) energy?
R
(a)
RH
R
H
R'
H
H
H
H
H
(b)
H
H
(c) H
H
H
R'
R'
R R'
(d) H
H
R
H
R'
(e)
H
H
H
H
H
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13
16. Axial vs. equatorial substituents.
Cyclohexane Conformations
Boat
Chair
Equatorial H atoms are pink, axial H atoms are blue
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Ring Strain in Cycloalkanes
propane
• Bond angles (at C atoms) 109.5o
cyclopropane
• Bond angles (at C atoms) 60o
• H-atoms are eclipsed
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Naming
Section 26-1
16
17. Naming
• Chemistry is a visual science: Structures
are key to understanding reactivity and
physical properties
• Systematic nomenclature: IUPAC rules
(assumed knowledge)
IUPAC: International Union of Pure and Applied Chemistry
See the supplementary information about naming
in ELM for more information
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Names of common compounds
O
O
Acetone
Acetaldehyde
Acetic acid
O
O
H
O
Formic acid
H
OH
OH
Ethyl acetate
Ether
OCH2CH3
CH3CH2OCH2CH3
O
Acetyl group
H3C
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Common compounds (continued)
Benzene
Toluene
OH
Phenol
Pyridine
N
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17
18. Some Common Alkyl Substituents
(Table 26.1)
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More alkyl names
n-butyl
R
sec-butyl
R
isobutyl
R
R
tert-butyl
Substituents
Vinyl groups
Allyl groups
R
R
R
Phenyl groups
Example: Allyl acetate
O
O
18
19. PH
Diagnostic iClicker Question
What is the name of this compound?
O
O
(a) sec-butyl acetate
(b) butyl methyl carboxylic acid
(c) ethyl butanoate
(d) isobutyl acetate
(e) n-butyl acetate
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PB
Diagnostic iClicker Question
What is the name of this compound?
O
O
(a) sec-butyl acetate
(b) propyl butanoate
(c) ethyl butanoate
(d) isobutyl acetate
(e) n-butyl propanoate
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JV
Diagnostic iClicker Question
What is the name of this compound?
O
O
(a) sec-butyl acetate
(b) butyl methyl carboxylic acid
(c) ethyl butanoate
(d) isobutyl acetate
(e) n-butyl acetate
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19
20. HS
Diagnostic iClicker Question
What is the name of this compound?
O
O
(a) sec-butyl acetate
(b) butyl methyl carboxylic acid
(c) ethyl butanoate
(d) isobutyl acetate
(e) n-butyl acetate
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Reactions of Alkanes
Section 26-2
Concept Check
C8H18(l) + O 2(g)
?
1) What are the products of the reaction at 298K?
2) Write a balanced chemical equation
3) Predict the signs of ∆H, ∆S and ∆G
4) What type of reaction is shown?
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20
22. Grignard Reagent
Mg
R X
Et2O
R MgX
X = Cl, Br or I
Mg
Cl
Et2O
MgCl
Look at the change in oxidation state of the Mg: Mg(0)
Question: What gets reduced?
Cl
Mg(II)
Mg2+ClChem
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Bonding in alkanes
Hybridization
Section 11-3
Review: Electronic Structure and Bonding
The following section, up to "Review: p-orbitals", is
assumed knowledge and will not be discussed in class.
The Atom: A dense nucleus surrounded by
a much larger extranuclear space
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22
23. Review: Principal Energy Levels
• Electrons are confined to shells defined by the
principal quantum number (n)
• n = 1, 2, 3 …
• Each shell can contain 2n2 electrons
• The lower the value of n-the lower the energy of
the shell (nearest to the nucleus)
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Review: Orbitals
• Shells are divided into sub-shells labelled
s, p, d, f
• p, d, and f orbitals are further divided up
based on their spatial orientation
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Review: Orbitals in Shells
Shell
n=1
n=2
Orbitals in that shell
1s
2s, 2px, 2py, 2pz
n=3
3s, 3px, 3py, 3pz, + 5 3d
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23
24. Review: Electron Configuration
Three principles/rules are used to
determine the electron configuration:
Aufbau Principle
Pauli Exclusion Principle
Hund’s rule
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Review: Orbitals (subshells)
• Each type of orbital (s, p, d, f) has a
distinct shape
• The shape represents the probability of
finding an electron (quantum mechanics)
• Organic chemists are interested in shells
1, 2, and sometimes 3
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Review: s-orbitals
Spherical:
24
25. Review: p-orbitals
3 of them: px, py, pz
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Example: Carbon
1s22s22p2
The outer most electrons of atoms (valence
electrons) govern the chemical and physical
properties
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p-Orbital Shapes
• The p-orbitals in carbon are at 90o to each
other
• Atoms bonding to a carbon atom should
therefore be situated at 90o to each other
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25
26. Methane - CH4
• Problem: the shape of methane is
tetrahedral (AX4)
• Bond angles are 109.5o not 90o
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Hybridization
•
Comes from the word hybrid which
means something of mixed origin or
composition
•
Hybrid orbitals arise by combination of
atomic orbitals within an atom
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sp3 Hybridization (section 11-3)
1s22s22p2
4 sp3 hybrid orbitals
Ground state
4 atomic orbitals
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26
27. sp3 Hybridization
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sp3 Hybridization
The number of hybrid orbitals is equal to
the number of combining atomic orbitals
Combine one 2s orbital and three 2p
orbitals
four sp3 orbitals
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Bonding-methane
Overlap of sp3 orbitals from carbon and 1sorbitals from hydrogen
109.5o
End-on (or end-to-end) overlap
produces sigma (σ) bonds.
End-on overlap of sp3-orbitals
also produces σ-bonds.
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27
28. PH
Diagnostic iClicker Question
How many σ-bonds are there in this
molecule?
H
H
H
H
H
H
(a) 1
(b) 2
(c) 7
(d) 14
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PB
Diagnostic iClicker Question
How many sp3-orbitals are there in this
molecule?
H
H
H
H
H
H
(a) 1
(b) 2
(c) 7
(d) 8
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JV
Diagnostic iClicker Question
How many sp3-sp3 σ-bonds are there in this
molecule?
(a) 1
(b) 2
(c) 7
(d) 14
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28
29. HS
Diagnostic iClicker Question
How many sp3-hybridized atoms are there in
this molecule?
(a) 2
(b) 6
(c) 8
(d) 26
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Moving beyond alkanes:
Functional Groups
Sample Problem
CO2H
H
N
H2N
O
OMe
O
What functional groups do you see?
29
30. Sample Problem: Solution
Ester
Carboxylic Acid
CO2H
H
N
H2N
O
OMe
O
Amine
Aromatic/Arene
Amide
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Table 26.2
*
p. 1080 * Not a functional group
Table 26.2
carboxylic acid
anhydride
O
R
O
O
O
R
H3 C
O
O
CH3
30
31. Table 26.2
You must be able to recognize these functional groups
91
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PH
Diagnostic iClicker Question
Which functional group is not found in this
molecule?
NH2
HO
N
(a) aryl
(b) amine
(c) amide
(d) phenol
H
92
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PB
Diagnostic iClicker Question
Which functional group is not found in this
molecule?
H
N
O
(a) aryl
(b) hydroxyl
(c) aryl halide
(d) ester
OH
OH
O
N
OH
F
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31
32. JV
Diagnostic iClicker Question
Which functional group is not found in this
molecule?
O
(a) amide
(b) ketone
(c) aryl halide
(d) alkene
H
N
N
H
Cl
O
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PB
Diagnostic iClicker Question
Which functional group is not found in this
molecule?
N
EtO
N
N
N
(a) aryl
(b) hydroxyl
(c) amine
(d) amide
S
NH
N
O
O
O
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Synthesis
1) Functional group interconversion
– ex. Converting an aldehyde to an alcohol
O
OH
H
2) Carbon-carbon bond forming reactions
– ex. Grignard reaction
R MgX
1. CO2
2. H3O+
R CO2H
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32
34. sp2 Hybrid Orbitals (section 11-4)
Combine one 2s orbital + two 2p orbitals
three sp2 orbitals (+ one 2p orbital left
over)
Hybrid orbital lobes pointing in the
direction of an equilateral triangle: bond
angles 120o
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sp2 Hybrid Orbitals
sp2 Hybrid Orbitals
• The extra p-orbital can be used to form πbonds
• π-bonds are covalent bonds that form by
the sideways overlap of parallel p-orbitals
eclipsed p-orbitals
π-bond
staggered p-orbitals
no π-bond
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34
35. Ethene
Section 11-4
Overlap above and below plane of
atoms gives 1 π bond
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Recall: Conformations of alkanes
Alkenes have restricted rotation
Geometric Isomers
cis
p. 1086
trans
35
36. Fats and Oils: Triacylglycerols
Fat: solid at room temp.
Oil: liquid at room temp.
O
OH
O
R
O
OH
O
R
OH
O
glycerol
R
O
Key Factors:
• Chain length (MW)
• Number of double bonds
• Geometry of the double
bonds
triacylglycerol
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(More information available on p. 1137-1139)
107
Concept Check
Which of these two fatty acids has the
higher melting point and why?
O
RO
Linoleic acid (R = H)
O
RO
Stearic acid (R = H)
Concept Check: Solution
O
RO
Linoleic acid (R = H)
mp = -5oC
Less efficient packing because of kink in chain geometry, therefore
weaker intermolecular forces and lower melting point.
O
RO
Stearic acid (R = H)
mp = 70oC
Straight chain allows more efficient packing, therefore stronger
intermolecular forces and higher melting point.
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36
38. PH
Formative iClicker Question #2
Which molecule has an E configuration?
(a)
Cl
(b)
F
(c)
Cl
(d)
(e)
F
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PB
Formative iClicker Question #2
Which molecule has an E configuration?
(a)
(b)
(c)
F
(d)
F
(e)
F
F
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JV
Formative iClicker Question #2
Which molecule has an E configuration?
(a)
(b)
(c)
Cl
(d)
Cl
(e)
Cl
Cl
Chem
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38
39. HS
Formative iClicker Question #2
Which molecule has an E configuration?
(a)
(b)
F
Cl
F
(c)
F
Cl
(d)
(e)
Cl
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Degree of Unsaturation
• A hydrocarbon with one π-bond or ring has two
fewer H-atoms than a linear alkane; it is said to
have “1 degree of unsaturation”
• The molecular formula of a hydrocarbon can be
used to determine the number of π-bonds and/or
rings in a compound.
• The "degree of unsaturation" (d.o.u.) can be
calculated using:
d.o.u. = (2n + 2 - m) / 2
(m = # of H-atoms, n = # of C-atoms)
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Degree of Unsaturation (d.o.u.)
• Rings count as one d.o.u.
• Double bonds count as one d.o.u.
• Triple bonds count as two degrees of
unsaturation
• d.o.u. does not give the type or number of each
type of unsaturation (ring, π bond); this is
determined using spectroscopic techniques (2nd
year)
• Note: a molecule can be saturated yet have a
degree of unsaturation (e.g., cyclohexane)
Chem
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39
40. PH
Diagnostic iClicker Question
Which molecule has the highest degree of
unsaturation?
(a)
(b)
(c)
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PB
Diagnostic iClicker Question
Which molecule has the highest degree of
unsaturation?
(a)
(b)
(c)
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119
JV
Diagnostic iClicker Question
Which molecule has the lowest degree of
unsaturation?
(a)
(b)
(c)
Chem
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40
41. HS
Diagnostic iClicker Question
Which molecule has the lowest degree of
unsaturation?
(a)
(b)
(c)
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Reactions involving
alkenes
Section 26-3
Addition Reactions
Not observed
Markovnikov’s rule: the H atom ends up attached to the
carbon atom of the double bond that has the most
hydrogen atoms to start with.
p. 1087-1088
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41
42. Explanation of Markovnikov’s rule
+
X
Br -
H
H Br
δ+
2o carbocation - less stable
δ-
H
+
Br -
3o carbocation - more stable
H
Br
haloalkane product
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Curly arrows
• The curly arrow represents electrons
moving from the alkene π-bond to the
proton of HBr, forming a C-H bond.
H Br
δ+
δ-
• We will examine this in more detail in
nucleophilic substitution reactions (Section
26-11)
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Carbocation stability
Stability:
H3C+
<
methyl
<
<
1°
<
<
2°
<
3°
Why do alkyl substituents increase cation stability?
Steric:
Br
H3C
H3C CH3
Br H3C
H3C
CH3
The cationic carbon rehybridizes from sp3 to sp2, relieving
the steric clash between substituents
Chem
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42
43. Carbocation stability
Why do alkyl substituents increase cation stability?
Electronic:
CH3
H3C
CH3
Alkyl substituents are electron donating compared with H.
Donating electrons to an electron deficient (positively
charged) centre stabilizes it.
δ+
δ-
= a permanent electric dipole
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PH
Formative iClicker Question #3
What is the expected product, according to
Markovnikov's rule?
HBr
Br
(a)
(b)
Br
Br
Br
Br
(c)
(d)
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PB
Formative iClicker Question #3
What is the expected product, according to
Markovnikov's rule?
HI
(a)
(b) I
I
I
I
(c)
I
(d)
Chem
1AA3
129
43
44. JV
Formative iClicker Question #3
What is the expected product, according to
Markovnikov's rule?
HBr
(b)
(a)
Br
Br
(c)
(d)
Br
Br
Chem
1AA3
130
HS
Formative iClicker Question #3
What is the expected product, according to
Markovnikov's rule?
HCl
Cl
(b)
(a)
Cl
Cl
Cl
(c)
(d)
Cl
Chem
1AA3
131
Hydration Reaction
• Addition is favoured (forward reaction) in dilute acid
• Elimination is favoured (reverse reaction) in concentrated acid
Chem
1AA3
132
44
45. Hydration also follows Markovnikov's rule
H
H 2O
HO
H
H3O+
H
+
O
H
JV?
H
+
HO
H3O+
H
H2O
O H
H
Chem
1AA3
133
Chem
1AA3
134
Reduction of Alkenes
Hydrogenation
H
H H
H
catalyst
Application: Hydrogenation of Natural Products
O
O
CH2OC(CH2)7CH
CH2OC(CH2)16CH3
CH(CH2)7CH3
O
O
CHOC(CH2)7CH
O
CH(CH2)7CH3
3H2
Ni catalyst
heat
CH2OC(CH2)16CH3
CH2OC(CH2)7CH CH(CH2)7CH3
Unsaturated vegetable oil
(olein-liquid)
CHOC(CH2)16CH3
O
Solid cooking fat-shortening
(stearin, solid)
(More information available on p. 1137-1139)
Chem
1AA3
135
45
46. Partial Hydrogenation
O
RO
H2 (1 equiv.)
catalyst
O
RO
mixture
H
saturated at either double bond, e.g.
H
Chem
1AA3
136
cis versus trans fatty acids
cis-9-octadecenoic acid
(Oleic acid)
trans-9-octadecenoic acid
(Elaidic acid)
Chem
1AA3
137
Alkynes
Section 26-3
46
47. Alkynes
According to VSEPR, alkynes are linear
Chem
1AA3
p. 1085
139
sp Hybrid Orbitals
• Combine one 2s orbital + one 2p orbital
two sp orbitals (+ two 2p orbitals left over)
sp hybridization
Section 11-4, p. 436
Chem
1AA3
140
Chem
1AA3
141
sp Hybrid Orbitals
47
48. Acetylene: Orbitals
• Acetylene, C2H2, has a triple bond.
• Linear at carbon
Chem
1AA3
142
Reactions of Alkynes
Reduction of Alkenes and Alkynes
H H
H
H
catalyst
CH3CH2C
CCH3
CH3CH2C
CCH3
+
H2
+
H2
Pd/C
CH3CH2CH2CH2CH3
Et
Lindlar's catalyst
H
CH3
H
Cis isomer only!
p. 1088
Chem
1AA3
144
48
49. The Carbonyl Group:
ketones and aldehydes
Section 26-6
Examples
CH3OH
Ketones
H3C
O
O
O
Acetone
Methyl ethyl ketone (MEK)
Aldehydes
Testosterone
O
O
O
H
H
H
H
Benzaldehyde
Formaldehyde
Cinnamaldehyde
Chem
1AA3
p. 1094-1095
146
Structure and Polarity
121o
H
O
121o
118o
H
118o
H
O
118o
124o
122o
CH3 H3C
O
O
116o
122o
CH3
δ-
δ+
R
R
Chem
1AA3
147
49
50. Synthesis and reactions of
aldehydes and ketones
Section 26-5, 26-6
Synthesis
Oxidation of alcohols:
[O]
O
OH
H
[O]
OH
O
Oxidation: Addition of an oxygen atom or removal of (a
molecule of) hydrogen
[O] = Oxidizing agent
Chem
1AA3
149
Primary, Secondary & Tertiary Alcohols
R CH2 OH
Primary (1o)
R CH OH
R'
Secondary (2o)
R''
R C
R'
OH
Tertiary (3o)
Chem
1AA3
150
50
51. Oxidation
• Primary alcohol
acid
aldehyde
carboxylic
O
OH
O
H
• Secondary alcohol
ketone
O
OH
• Tertiary alcohol
OH
no reaction
– a C-C bond would have to break in order for oxidation
to occur
Chem
151
1AA3
PH
Formative iClicker Question #4
What is the expected product of oxidation of
2,2-dimethylpropanol?
(a)
(b)
(c)
(d)
2,2-dimethylpropanoic acid
2,2-dimethylpropanone
2-methyl-2-propanal
no reaction
Chem
1AA3
152
PB
Formative iClicker Question #4
What is the expected product of oxidation of
s-pentanol?
(a)
(b)
(c)
(d)
methyl butyl ketone
2-pentanone
pentanoic acid
none of the above
Chem
1AA3
153
51
52. JV
Formative iClicker Question #4
What is the expected product of oxidation of
isopentanol?
(a)
(b)
(c)
(d)
methyl butyl ketone
2-pentanone
4-methyl pentanoic acid
none of the above
Chem
1AA3
154
HS
Formative iClicker Question #4
What is the expected product of oxidation of
2-methylbutanol?
(a)
(b)
(c)
(d)
2-methylbutanoic acid
2-methylbutanone
s-pentanoic acid
none of the above
Chem
1AA3
155
Oxidizing Agents
• Commonly metals in high oxidation states
(transfer of 2 to 4 electrons)
e.g., MnO4-, Cr2O72- (KMnO4, K2Cr2O7)
• Usually done in acid or base to facilitate
electron transfer
• Pyridinium chlorochromate (PCC)
– Specific for oxidizing 1o alcohols
aldehydes
Chem
1AA3
156
52
53. Metabolism of Alcohol: Detoxification
Enzymatic Detoxification by Two-step Oxidation
ethanol rapidly distributes from blood to tissues/organs
two-step oxidation of ethanol
acetaldehyde
brain
acetic acid
acetic acid is eliminated by kidneys or metabolized into energy
"One of the disadvantages of wine is that it makes a man
mistake words for thoughts." -- Samuel Johnson
Chem
1AA3
157
Metabolism of Alcohol: Detoxification
Enzymatic Detoxification by Two-step Oxidation
toxic intermediate
oxidizing agent
Alcohol
Dehydrogenase
+
OH + NAD
O
H
O
H
Acetaldehyde
Dehydrogenase
+ NAD+
+ NADH + H+
O
OH
+ NADH + H+
non-toxic final product
Chem
1AA3
158
Addition Reactions to the Carbonyl Group
Reduction: NaBH4 is a source of H- (hydride)
O
1. NaBH4
H
OH
2. H3O+
1o alcohol
aldehyde
O
ketone
p. 1096
1. NaBH4
OH
2. H3O+
2o alcohol
Chem
1AA3
159
53
54. Synthesis and Reactions of
Carboxylic Acids and
Derivatives
Section 26-7
Examples
Chem
1AA3
p. 1097
161
Chem
1AA3
162
Carboxylic Acid: Structure
54
55. Synthesis and Reactivity
Section 26-7
Carboxylic acids
Weak acids:
O
O
+
H2O
+
H2O
NaOH
OH
O
Ka = 1.4x10−5
H3O+
+
O-
O
OH
O-
+
+
Na+ H3O 2O
+ H
Derivatives:
O
O
R
Cl
R
Acid chloride
O
O
O
R
R
Anhydride
O
O R
R
NHR
Amide
Ester
Chem
1AA3
164
Preparation of Esters
O
+
OH
H+
CH3CH2OH
• Fischer
O
OCH2CH3
+
H2O
Esterification
• Acid catalyst
• Condensation reaction
p. 1098
Chem
1AA3
165
55
56. Hydrolysis of Esters
O
OCH2CH3
+
O
H+
H2O
+
CH3CH2OH
OH
• Reverse of previous reaction
• Also requires acid catalyst
Chem
1AA3
166
Acid chlorides
O
Carboxylic acid
R
Acid chloride
O
R NH2
R
OH
O
O
R
Acid-base
reaction
+
O- H3N R
+
Cl
R NH2
R
+
HCl
+
HCl
NH R
amide
O
R
O
Cl
+
R OH
R
O
R
ester
Chem
1AA3
167
Chem
1AA3
168
Acetyl Group
p. 1097
56
57. Synthesis
Section 26-12
Concept Check: Synthesis
Fill in the missing reagents:
O
OH
Chem
1AA3
170
Chem
1AA3
171
Concept Check: Solution
O
1. NaBH4
OH
conc. H2SO4, ∆
2. H3O+
57
58. PH
Formative iClicker Question #4
What are conditions i and ii?
i
OH
O
ii
i
ii
(a)
Lindlar's catalyst
KMnO4
(b)
PCC
10% H2SO4
(c)
NaBH4
KMnO4
(d)
NaBH4
PCC
Chem
1AA3
172
PB
Formative iClicker Question #4
i
What are conditions i and ii?
OH
ii
i
ii
10% H2SO4
conc. H2SO4
(b)
PCC
10% H2SO4
(c)
10% H2SO4
H2/Pd-C
(d)
conc. H2SO4
10% H2SO4
(a)
Chem
1AA3
173
JV
Formative iClicker Question #4
What are conditions i and ii?
i
ii
Cl
i
ii
(a)
PCC
Cl2
(b)
H2/Pd-C
HCl
(c)
H2/Pd-C
Cl2
(d)
Lindlar's catalyst
HCl
Chem
1AA3
174
58
59. HS
Formative iClicker Question #4
What are conditions i and ii?
i
ii
i
ii
(a)
H2/Pd-C
PCC
(b)
KMnO4
PCC
(c)
H2/Pd-C
Lindlar's catalyst
(d)
Lindlar's catalyst
H2/Pd
Chem
1AA3
175
Substitution Reactions and
Mechanisms
Section 26-11
Chemical Reactions
• Charge attraction draws molecules together
• In organic chemistry, there is often not a cation
reacting with an anion
• It is more common to have a charged reagent be
attracted to an organic compound that has a
dipole
– e.g., NaCN + acetone (polarized C=O bond generating
an electropositive carbon atom that attracts the CN-)
Chem
1AA3
177
59
60. Chemical Reactions Continued
• The reagent does not necessarily need to
be charged: Lone electron pairs would
also be attracted to a dipole
Chem
1AA3
178
Chem
1AA3
179
Chemical Reactions
• The majority of reactions in organic
chemistry involve the flow of electrons
from one molecule to another
• nucleophile (nucleus loving) = electron
donor = Lewis base
• electrophile (electron loving) = electron
acceptor = Lewis acid
p. 1108
Chemical Reactions
• In most organic reactions the orbitals of
the nucleophile and electrophile are
directional
therefore the two orbitals
must be correctly aligned for a reaction to
occur
Chem
1AA3
180
60
61. Substitution Reactions at sp3 Hybridized Carbon
Charged nucleophiles
Neutral nucleophiles
Chem
1AA3
181
Mechanism
• The flow of electrons between a
nucleophile and electrophile can be
represented by a double-headed curly
arrow
NH3
E+
• The result of the movement is to form a
bond between an electrophile and a
nucleophile
NH3
H
+
H N E
H
E+
Chem
1AA3
182
Mechanism (continued)
• The arrow tail starts at the source of the
moving electrons and the arrow head
indicates its final destination
NH3
E+
Chem
1AA3
183
61
62. SN2 Mechanism
S = substitution; N = nucleophilic, 2 = bimolecular
Rate = k[OH-][CH3Cl]
p. 1111
Chem
1AA3
184
PH
Diagnostic iClicker Question
What are the nucleophile and the electrophile in this reaction?
CH3Cl + Br-
Cl- + CH3Br
Nucleophile
Electrophile
(a)
Cl-
CH3Br
(b)
CH3Br
Cl-
(c)
Cl-
Br-
(d)
Br-
CH3Cl
Chem
1AA3
185
PB
Diagnostic iClicker Question
What are the nucleophile and the electrophile in this reaction?
H3C-NH2 + CH3Cl
H3C-NH-CH3 + HCl
Nucleophile
Electrophile
(a)
CH3Cl
H3C-NH-CH3
(b)
CH3NH2
CH3Cl
(c)
CH3NH2
Cl-
(d)
Cl-
H+
Chem
1AA3
186
62
63. JV
Diagnostic iClicker Question
What are the nucleophile and the electrophile in this reaction?
H3C-NH-CH3 + HCl
H3C-NH2 + CH3Cl
Nucleophile
Electrophile
(a)
CH3NH2
H3C-NH-CH3
(b)
CH3Cl
Cl-
(c)
CH3NH2
CH3Cl
(d)
H3C-NH-CH3
H+
Chem
1AA3
187
HS
Diagnostic iClicker Question
What are the nucleophile and the electrophile in this reaction?
CH3Cl + Br-
Cl- + CH3Br
Nucleophile
Electrophile
(a)
Cl-
Br-
(b)
CH3Cl
Cl-
(c)
Cl-
CH3Cl
(d)
Br-
ClChem
1AA3
188
Chem
1AA3
189
SN2 Mechanism
δ-
δ-
More on mechanisms in the next section
63
64. SN2: Inversion of Configuration
Chem
1AA3
190
Chem
1AA3
191
SN1 Mechanism (unimolecular)
p. 1112
slow
SN1 Mechanism
t
fas
t
fas
Rate = k [(CH3)3CBr]
Chem
1AA3
192
64
65. SN1 versus SN2
• The mechanism depends on many factors,
but as a general rule of thumb:
• 1o electrophile = SN2
– less stable carbocation intermediate, less steric
hindrance to nucleophilic attack
• 2o electrophile = ?
– hard to predict (you will see this next year)
• 3o electrophile = SN1
– more stable carbocation intermediate, more
steric hindrance to nucleophilic attack
Chem
1AA3
193
PH
Formative iClicker Question #5
Rank the likelihood of the following compounds to
undergo SN2 nucleophilic substitutions:
Cl
Cl
Cl
i
(a)
(b)
(c)
(d)
i
i
i
i
<
>
>
≈
ii
ii
ii
ii
≈
>
≈
>
ii
iii
iii
iii
iii
iii
Chem
1AA3
194
PB
Formative iClicker Question #5
Rank the likelihood of the following compounds to
undergo SN2 nucleophilic substitutions:
i
(a)
(b)
(c)
(d)
iii
i
i
ii
≈
≈
>
>
ii
ii
iii
i
ii
<
>
>
<
Cl
Cl
Cl
iii
i
iii
ii
iii
Chem
1AA3
195
65
66. JV
Formative iClicker Question #5
Rank the likelihood of the following compounds to
undergo SN2 nucleophilic substitutions:
Cl
Cl
i
(a)
(b)
(c)
(d)
iii
i
i
ii
≈
≈
>
>
ii
ii
ii
i
Cl
ii
>
>
≈
<
iii
i
iii
iii
iii
Chem
1AA3
196
HS
Formative iClicker Question #5
Rank the likelihood of the following compounds to
undergo SN2 nucleophilic substitutions:
Cl
Cl
Cl
i
(a)
(b)
(c)
(d)
i
i
i
ii
≈
≈
<
≈
iii
ii
ii
i
ii
<
<
>
>
iii
ii
iii
iii
iii
Chem
1AA3
197
66