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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
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
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
Organic Compounds: Biological

11-cis-retinal
H

O

NH2

Serotonin
(neurotransmitter)

HO
N
H

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Diagnostic iClicker Question
Which is the cis double bond in 11-cis-retinal?

(b)

(d)

(c)

(a)

(e)
H

O
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11

Organic Compounds: Medicines
N

EtO

O

Me2N

N

N
N

S
NH

N

O

O

O

Tamoxifen
H
N
O

OH
N

Lipitor

Viagra
OH

O
OH

F
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4
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
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
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
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

Chem
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PH

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

Chem
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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
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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25

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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Chem
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Fuels: Octane Number

Octane Number: used to indicate the resistance of a
motor fuel to “knock”

p. 1084

9
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
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
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

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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
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

Chem
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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
Ring Structures: Cycloalkanes
CnH2n

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Molecules are not always flat: Cyclohexane

Boat

Chair
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Boat conformation movie

14
Boat conformation movie

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Chair conformation movie

Chair conformation movie

15
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
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
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
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
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
Concept Check: Solution

C8H18(l) +

25
2

O2(g) → 8 CO2(g) + 9 H2O(l)

∆H° = -5.48 × 103 kJ mol−1 (exothermic!)
∆So is negative
∆Go = ∆H°-T∆So, ∆Go should be negative (∆H° is large)
Reaction type: Combustion, redox
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Halogenation
CH4

X2

CH3X + HX + CH3-CH3

Light or heat

Halogenation
Initiation:
Propagation:

Cl-Cl

∆ or hν

→

2 Cl·

H3C-H + Cl· → H3C· + HCl
H3C· + Cl2 → H3C-Cl + Cl·

Termination:

Cl· + Cl· → Cl-Cl
H3C· + Cl· → H3C-Cl
H3C· + H3C· → H3C-CH3

Applicable also for F2 (often explosive), Br2, I2 (slow)
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21
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
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
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
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
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
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
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
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
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
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

Chem
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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

Chem
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93

31
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
Alkenes

Section 26-3

Alkenes (CnH2n)

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Multiple Covalent Bonds
• Ethylene has a double bond in its Lewis
structure
• VSEPR says trigonal planar shape at C

sp2 hybridization

p. 435

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33
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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101

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
Ethene

Section 11-4

Overlap above and below plane of
atoms gives 1 π bond

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105

Recall: Conformations of alkanes

Alkenes have restricted rotation

Geometric Isomers

cis
p. 1086

trans

35
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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Chem
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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.

Chem
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36
Impact of Geometry

Chem
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The E,Z System of Nomenclature

• Need a new system

• Higher priority

higher atomic number

Z isomer

E isomer

p. 1106

Concept Check

Label the tamoxifen isomers as E or Z:
Me2N
Me2N

O

O

Z

E

37
PH

Formative iClicker Question #2
Which molecule has an E configuration?

(a)

Cl

(b)
F

(c)

Cl

(d)

(e)
F

Chem
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PB

Formative iClicker Question #2
Which molecule has an E configuration?
(a)

(b)

(c)
F

(d)

F

(e)
F

F

Chem
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113

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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114

38
HS

Formative iClicker Question #2
Which molecule has an E configuration?
(a)

(b)
F

Cl

F

(c)
F

Cl

(d)

(e)
Cl

Chem
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115

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)
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39
PH

Diagnostic iClicker Question
Which molecule has the highest degree of
unsaturation?
(a)

(b)

(c)

Chem
1AA3

118

PB

Diagnostic iClicker Question
Which molecule has the highest degree of
unsaturation?
(a)

(b)

(c)

Chem
1AA3

119

JV

Diagnostic iClicker Question
Which molecule has the lowest degree of
unsaturation?
(a)

(b)

(c)

Chem
1AA3

120

40
HS

Diagnostic iClicker Question
Which molecule has the lowest degree of
unsaturation?
(a)

(b)

(c)

Chem
1AA3

121

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

Chem
1AA3

123

41
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

Chem
1AA3

124

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)
Chem
1AA3

125

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

126

1AA3

42
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

Chem
1AA3

127

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)
Chem
1AA3

128

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
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
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
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
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
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
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
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
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
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
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
Synthesis and Reactions of
Carboxylic Acids and
Derivatives

Section 26-7

Examples

Chem
1AA3

p. 1097

161

Chem
1AA3

162

Carboxylic Acid: Structure

54
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
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
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
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
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
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
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
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
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
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
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
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

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Chapter 26 skeleton notes

  • 1. Organic Chemistry Selected sections Ch 26 + Ch 11 The chemistry of life and living things The chemistry of carbon compounds Chem 1AA3 2 Chem 1AA3 3 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 Chem 1AA3 4 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! Chem 1AA3 5 Medical Application: Molecular Imaging 18F-fluorodeoxyglucose Chem 1AA3 6 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 Chem 1AA3 7 Components (continued) 3) Synthesis: How to design new molecules – and then make them Chem 1AA3 8 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 Chem 1AA3 9 3
  • 4. Organic Compounds: Biological 11-cis-retinal H O NH2 Serotonin (neurotransmitter) HO N H Chem 1AA3 10 Diagnostic iClicker Question Which is the cis double bond in 11-cis-retinal? (b) (d) (c) (a) (e) H O Chem 1AA3 11 Organic Compounds: Medicines N EtO O Me2N N N N S NH N O O O Tamoxifen H N O OH N Lipitor Viagra OH O OH F Chem 1AA3 12 4
  • 5. Organic Compounds: Drugs CH3 OH CH3 CH3 HN N H Stanozolol Chem 1AA3 13 Organic Compounds: Industrial Chemicals HN Indigo dye (blue jeans) O O NH CO2H H N H 2N O Aspartame OMe O Chem 1AA3 14 Organic Compounds: Natural Products O O N Cocaine O O N HO Quinine MeO N Chem 1AA3 15 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): Chem 1AA3 17 Chem 1AA3 18 Ethane (C2H6) 6
  • 7. Propane (C3H8) Chem 1AA3 19 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 Chem 1AA3 20 Drawing molecules (continued) • Guideline 3: For reactions, draw out the functional groups in detail and include lone pairs (electrons) OH O Chem 1AA3 21 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 Chem 1AA3 PH 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 Chem 1AA3 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 Chem 1AA3 24 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 Chem 1AA3 25 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 Chem 1AA3 26 Chem 1AA3 27 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 Chem 1AA3 28 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 Chem 1AA3 30 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 Chem 1AA3 31 Conformations of alkanes Newman Projections Lower E Chem 1AA3 32 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 Chem 1AA3 33 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 Chem 1AA3 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 1AA3 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 Chem 1AA3 36 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 1AA3 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 Chem 1AA3 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 Chem 1AA3 39 13
  • 14. Ring Structures: Cycloalkanes CnH2n Chem 1AA3 40 Molecules are not always flat: Cyclohexane Boat Chair Chem 1AA3 41 Chem 1AA3 42 Boat conformation movie 14
  • 15. Boat conformation movie Chem 1AA3 43 Chem 1AA3 44 Chem 1AA3 45 Chair conformation movie Chair conformation movie 15
  • 16. Axial vs. equatorial substituents. Cyclohexane Conformations Boat Chair Equatorial H atoms are pink, axial H atoms are blue Chem 1AA3 46 Ring Strain in Cycloalkanes propane • Bond angles (at C atoms) 109.5o cyclopropane • Bond angles (at C atoms) 60o • H-atoms are eclipsed Chem 1AA3 47 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 Chem 1AA3 49 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 Chem 1AA3 50 Common compounds (continued) Benzene Toluene OH Phenol Pyridine N Chem 1AA3 51 17
  • 18. Some Common Alkyl Substituents (Table 26.1) Chem 1AA3 52 Chem 1AA3 53 Chem 1AA3 54 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 Chem 1AA3 55 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 Chem 1AA3 56 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 Chem 1AA3 57 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 Chem 1AA3 58 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? Chem 1AA3 60 20
  • 21. Concept Check: Solution C8H18(l) + 25 2 O2(g) → 8 CO2(g) + 9 H2O(l) ∆H° = -5.48 × 103 kJ mol−1 (exothermic!) ∆So is negative ∆Go = ∆H°-T∆So, ∆Go should be negative (∆H° is large) Reaction type: Combustion, redox Chem 1AA3 61 Chem 1AA3 62 Halogenation CH4 X2 CH3X + HX + CH3-CH3 Light or heat Halogenation Initiation: Propagation: Cl-Cl ∆ or hν → 2 Cl· H3C-H + Cl· → H3C· + HCl H3C· + Cl2 → H3C-Cl + Cl· Termination: Cl· + Cl· → Cl-Cl H3C· + Cl· → H3C-Cl H3C· + H3C· → H3C-CH3 Applicable also for F2 (often explosive), Br2, I2 (slow) Chem 1AA3 63 21
  • 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 1AA3 64 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 Chem 1AA3 66 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) Chem 1AA3 67 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 Chem 1AA3 68 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 Chem 1AA3 69 23
  • 24. Review: Electron Configuration Three principles/rules are used to determine the electron configuration: Aufbau Principle Pauli Exclusion Principle Hund’s rule Chem 1AA3 70 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 Chem 1AA3 71 Chem 1AA3 72 Review: s-orbitals Spherical: 24
  • 25. Review: p-orbitals 3 of them: px, py, pz Chem 1AA3 73 Example: Carbon 1s22s22p2 The outer most electrons of atoms (valence electrons) govern the chemical and physical properties Chem 1AA3 74 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 Chem 1AA3 75 25
  • 26. Methane - CH4 • Problem: the shape of methane is tetrahedral (AX4) • Bond angles are 109.5o not 90o Chem 1AA3 76 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 Chem 1AA3 77 sp3 Hybridization (section 11-3) 1s22s22p2 4 sp3 hybrid orbitals Ground state 4 atomic orbitals Chem 1AA3 78 26
  • 27. sp3 Hybridization Chem 1AA3 79 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 Chem 1AA3 80 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. Chem 1AA3 81 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 Chem 1AA3 82 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 Chem 1AA3 83 JV Diagnostic iClicker Question How many sp3-sp3 σ-bonds are there in this molecule? (a) 1 (b) 2 (c) 7 (d) 14 Chem 1AA3 84 28
  • 29. HS Diagnostic iClicker Question How many sp3-hybridized atoms are there in this molecule? (a) 2 (b) 6 (c) 8 (d) 26 Chem 1AA3 85 Chem 1AA3 87 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 Chem 1AA3 88 Chem 1AA3 89 Chem 1AA3 90 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 Chem 1AA3 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 Chem 1AA3 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 Chem 1AA3 93 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 Chem 1AA3 94 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 Chem 1AA3 95 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 Chem 1AA3 96 32
  • 33. Alkenes Section 26-3 Alkenes (CnH2n) Chem 1AA3 98 Multiple Covalent Bonds • Ethylene has a double bond in its Lewis structure • VSEPR says trigonal planar shape at C sp2 hybridization p. 435 Chem 1AA3 99 33
  • 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 Chem 1AA3 100 Chem 1AA3 101 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 Chem 1AA3 102 34
  • 35. Ethene Section 11-4 Overlap above and below plane of atoms gives 1 π bond Chem 1AA3 103 Chem 1AA3 104 Chem 1AA3 105 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 Chem 1AA3 106 Chem 1AA3 (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. Chem 1AA3 108 36
  • 37. Impact of Geometry Chem 1AA3 109 Chem 1AA3 110 Chem 1AA3 111 The E,Z System of Nomenclature • Need a new system • Higher priority higher atomic number Z isomer E isomer p. 1106 Concept Check Label the tamoxifen isomers as E or Z: Me2N Me2N O O Z E 37
  • 38. PH Formative iClicker Question #2 Which molecule has an E configuration? (a) Cl (b) F (c) Cl (d) (e) F Chem 1AA3 112 PB Formative iClicker Question #2 Which molecule has an E configuration? (a) (b) (c) F (d) F (e) F F Chem 1AA3 113 JV Formative iClicker Question #2 Which molecule has an E configuration? (a) (b) (c) Cl (d) Cl (e) Cl Cl Chem 1AA3 114 38
  • 39. HS Formative iClicker Question #2 Which molecule has an E configuration? (a) (b) F Cl F (c) F Cl (d) (e) Cl Chem 1AA3 115 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) Chem 1AA3 116 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 1AA3 117 39
  • 40. PH Diagnostic iClicker Question Which molecule has the highest degree of unsaturation? (a) (b) (c) Chem 1AA3 118 PB Diagnostic iClicker Question Which molecule has the highest degree of unsaturation? (a) (b) (c) Chem 1AA3 119 JV Diagnostic iClicker Question Which molecule has the lowest degree of unsaturation? (a) (b) (c) Chem 1AA3 120 40
  • 41. HS Diagnostic iClicker Question Which molecule has the lowest degree of unsaturation? (a) (b) (c) Chem 1AA3 121 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 Chem 1AA3 123 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 Chem 1AA3 124 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) Chem 1AA3 125 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 126 1AA3 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 Chem 1AA3 127 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) Chem 1AA3 128 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