chapter 26 skeleton notes

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Organic Chemistry Selected sections Ch 26 + Ch 11 The chemistry of life and living things The chemistry of carbon compounds 2 Chem 1AA3 3 Chem 1AA3 Evolution of the field

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Page 1: Chapter 26   skeleton notes

1

Organic ChemistrySelected sections Ch 26 + Ch 11

The chemistry of life and living things

The chemistry of carbon compounds

22Chem1AA3

33Chem1AA3

Evolution of the field

Page 2: Chapter 26   skeleton notes

2

44Chem1AA3

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

55Chem1AA3

Why is organic chemistry important?

• Because it is central to:ChemistryChemical BiologyBiochemistryBiologyEngineeringMaterial sciencesForensic SciencesMedicine

• To get into graduate/medical/dental school!

66Chem1AA3

Medical Application: Molecular Imaging

18F-fluorodeoxyglucose

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77Chem1AA3

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

88Chem1AA3

Components (continued)

3) Synthesis: How to design new molecules – and then make them

99Chem1AA3

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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1010Chem1AA3

Organic Compounds: Biological

OH

11-cis-retinal

Serotonin(neurotransmitter)

NH

NH2

OH

1111Chem1AA3

Diagnostic iClicker Question

Which is the cis double bond in 11-cis-retinal?

OH

(a)

(b)(c)

(d)

(e)

1212Chem1AA3

Organic Compounds: Medicines

Tamoxifen Viagra

OMe2N

NN NH

N

O

SO O

N

NEtO

N OH

NH

O

F

OH OH O

Lipitor

Page 5: Chapter 26   skeleton notes

5

1313Chem1AA3

Organic Compounds: Drugs

Stanozolol

NHN

OHCH3

CH3

CH3

H

1414Chem1AA3

Organic Compounds: Industrial Chemicals

Indigo dye (blue jeans)NH O

NHO

NH2

NH

O

CO2H O

OMeAspartame

1515Chem1AA3

Organic Compounds: Natural Products

NOH

N

MeO

Quinine

CocaineN

O

O

OO

Page 6: Chapter 26   skeleton notes

6

Alkanes

Section 26-1, 26-2

1717Chem1AA3

Alkanes

• Hydrocarbons – the simplest organic compounds (CnH2n+2)

• Saturated (use all bonding e− to make single bonds)

• Methane (various representations):

1818Chem1AA3

Ethane (C2H6)

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1919Chem1AA3

Propane (C3H8)

2020Chem1AA3

Drawing Organic Molecules

• Guideline 1: Draw molecules in a Zig-Zag shape versus linear structures

• Guideline 2: You can assume there are H-atoms attached to carbon atoms in a Zig-Zag structure giving a valence of 4

vs CH3CH2CH2CH2CH2CH3

OH OHH H

H H

H

HH

2121Chem1AA3

Drawing molecules (continued)

• Guideline 3: For reactions, draw out the functional groups in detail and include lone pairs (electrons)

OHO

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2222Chem1AA3

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

2323Chem1AA3

Diagnostic iClicker Question

Which of the following wedge-and-dash drawings of propane is incorrect?

(a)

(c)

H

H

H

H

HHH

H

H

HH

H H

HHH

HH

H

H

H

H

HH

HH

H

H

HHH

H

(b)

(d) (e) don't know

PH

2424Chem1AA3

Diagnostic iClicker Question

Which of the following wedge-and-dash drawings of propane is incorrect?

(a)

(c)

H

H

H

H

HHH

H

H H

HH

H H

H

H

HH H

H H

H HH

HH

H

H

HHH

H

(b)

(d) (e) don't know

PB

Page 9: Chapter 26   skeleton notes

9

2525Chem1AA3

Diagnostic iClicker Question

Which of the following wedge-and-dash drawings of propane is incorrect?

(a)

(c)

H

H

H

H

HHH

H

H

HH

H H

HHHH

H

H

H

H

H

HH

HH

H

H

HHH

H

(b)

(d) (e) don't know

JV

2626Chem1AA3

Diagnostic iClicker Question

Which of the following wedge-and-dash drawings of propane is incorrect?

HH

H

H

HH

H

H HH

H H

HH

H

H

H HH

HH

HHH

HH

H

H

HHH

H

(a) (c)(b)

(d) (e) don't know

HS

2727Chem1AA3

Fuels: Octane Number

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

p. 1084

Page 10: Chapter 26   skeleton notes

10

2828Chem1AA3

Fuels: Alcohols

Alcohols can also be used as fuels:

CH3OH(l) + 1.5O2(g) CO2(g) + 2H2O(l)

CH3CH2OH(l) + 3O2(g) 2CO2(g) + 3H2O(l)

∆Ho = -726 kJ mol-1

∆Ho = -1367 kJ mol-1

∆H°(combustion) forCH4, methane -891 kJ/molC2H6, ethane -1560 kJ/mol

http://pubs.acs.org/cen/coverstory/85/8551cover.html

Structural Diversity

Isomers, cycloalkanes

3030Chem1AA3

Concept Check: Skeletal/Structural Isomerism

Concept check:

Draw structural isomers of C5H12

Skeletal or structural isomers have:

- The same molecular formula but different connectivity.

- Different physical properties.

Page 11: Chapter 26   skeleton notes

11

3131Chem1AA3

Concept Check: Solution

C C C C CH

HH

H

H

H

H

H

H H

HH

H C C C CH

H

H

C

H

H H

HH

HH

H

H C C CH

H

C

C

H

HH

HH

H HH

H

pentane

2-methylbutane

2,2-dimethylpropane

3232Chem1AA3

Conformations of alkanes

Newman Projections

Lower E

3333Chem1AA3

• 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.

Conformation versus configuration

versus

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3434Chem1AA3

Conformations of ‘disubstituted ethane’

R'

H HR

HHH

H R'R

HHH

R' HR

HH

Staggered

Lowest E

RR'

H H

H H

3535Chem1AA3

Eclipsed Conformations

H

R'

H

R

HHH

H

R'

R

HHR'

H

H

R

HH

Eclipsed

Highest E

• All eclipsed conformations have higher energy than all staggered conformations.

3636Chem1AA3

Formative iClicker Question #1

Which conformation has the lowest (most favourable) energy?

R'

H HR

HH

H

H R'R

HH

R'

H

HR

HHH

H

R'R

HH

R'

H

R

HH

H

(a) (b) (c)

(d) (e)

PH

Page 13: Chapter 26   skeleton notes

13

3737Chem1AA3

Formative iClicker Question #1

Which conformation has the highest (least favourable) energy?

R'

H HR

HH

H

H R'R

HH

R'

H

HR

HHH

H

R'R

HH

R'

H

R

HH

H

(a) (b) (c)

(d) (e)

PB

3838Chem1AA3

Formative iClicker Question #1

Which conformation has the highest (least favourable) energy?

R'

H HR

HHH

H R'R

HHR'

H

HR

HH

H

H

R'R

HH

R'

H

R

HH

H

(a) (b) (c)

(d) (e)

JV

3939Chem1AA3

Formative iClicker Question #1

Which conformation has the lowest (most favourable) energy?

R'

H HR

HHH

H R'R

HHR'

H

HR

HH

H

H

R'R

HH

R'

H

R

HH

H

(a) (b) (c)

(d) (e)

HS

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14

4040Chem1AA3

Ring Structures: Cycloalkanes

CnH2n

4141Chem1AA3

Molecules are not always flat: Cyclohexane

Boat Chair

4242Chem1AA3

Boat conformation movie

Page 15: Chapter 26   skeleton notes

15

4343Chem1AA3

Boat conformation movie

4444Chem1AA3

Chair conformation movie

4545Chem1AA3

Chair conformation movie

Page 16: Chapter 26   skeleton notes

16

4646Chem1AA3

Cyclohexane Conformations

Axial vs. equatorial substituents.

Boat Chair

Equatorial H atoms are pink, axial H atoms are blue

4747Chem1AA3

Ring Strain in Cycloalkanes

propane cyclopropane

• Bond angles (at C atoms) 109.5o • Bond angles (at C atoms) 60o

• H-atoms are eclipsed

Naming

Section 26-1

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4949Chem1AA3

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

5050Chem1AA3

Names of common compounds

Acetone

Acetaldehyde

Formic acid

Acetic acid

Ethyl acetate

Ether

OCH2CH3

O

OH

O

H OH

O

H

O

O

CH3CH2OCH2CH3

H3C

OAcetyl group

5151Chem1AA3

Common compounds (continued)

Benzene

Toluene

Phenol

Pyridine

OH

N

Page 18: Chapter 26   skeleton notes

18

5252Chem1AA3

Some Common Alkyl Substituents (Table 26.1)

5353Chem1AA3

More alkyl names

R

R

R

R

n-butyl

sec-butyl

isobutyl

tert-butyl

5454Chem1AA3

Substituents

Vinyl groups

Allyl groups

Phenyl groups

Example: Allyl acetate

R

R

R

O

O

Page 19: Chapter 26   skeleton notes

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5555Chem1AA3

Diagnostic iClicker Question

What is the name of this compound?

(a) sec-butyl acetate(b) butyl methyl carboxylic acid(c) ethyl butanoate(d) isobutyl acetate(e) n-butyl acetate

O

O

PH

5656Chem1AA3

Diagnostic iClicker Question

What is the name of this compound?

(a) sec-butyl acetate(b) propyl butanoate(c) ethyl butanoate(d) isobutyl acetate(e) n-butyl propanoate

O

O

PB

5757Chem1AA3

Diagnostic iClicker Question

What is the name of this compound?

(a) sec-butyl acetate(b) butyl methyl carboxylic acid(c) ethyl butanoate(d) isobutyl acetate(e) n-butyl acetate

O

O

JV

Page 20: Chapter 26   skeleton notes

20

5858Chem1AA3

Diagnostic iClicker Question

What is the name of this compound?

(a) sec-butyl acetate(b) butyl methyl carboxylic acid(c) ethyl butanoate(d) isobutyl acetate(e) n-butyl acetate

O

O

HS

Reactions of Alkanes

Section 26-2

6060Chem1AA3

Concept Check

C8H18(l) + O2(g) ?

1) What are the products of the reaction at 298K?2) Write a balanced chemical equation3) Predict the signs of ∆H, ∆S and ∆G4) What type of reaction is shown?

Page 21: Chapter 26   skeleton notes

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6161Chem1AA3

Concept Check: Solution

C8H18(l) + O2(g) → 8 CO2(g) + 9 H2O(l)252

∆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

6262Chem1AA3

Halogenation

CH4

X2

Light or heatCH3X + HX + CH3-CH3

6363Chem1AA3

Halogenation

Initiation:

Propagation:

Termination:

H3C· + Cl·→ H3C-Cl

Cl· + Cl· → Cl-Cl

H3C· + H3C·→ H3C-CH3

Cl-Cl → 2 Cl·∆ or hν

H3C-H + Cl· → H3C· + HCl

H3C· + Cl2 → H3C-Cl + Cl·

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

Page 22: Chapter 26   skeleton notes

22

6464Chem1AA3

Grignard Reagent

R XMg

Et2OR MgX

ClMg

Et2OMgCl

Look at the change in oxidation state of the Mg: Mg(0) Mg(II)

X = Cl, Br or I

Question: What gets reduced?Cl Mg2+Cl-

Bonding in alkanes

Hybridization

Section 11-3

6666Chem1AA3

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

Page 23: Chapter 26   skeleton notes

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6767Chem1AA3

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)

6868Chem1AA3

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

6969Chem1AA3

Review: Orbitals in Shells

Shell Orbitals in that shelln = 1 1sn = 2 2s, 2px, 2py, 2pz

n = 3 3s, 3px, 3py, 3pz, + 5 3d

Page 24: Chapter 26   skeleton notes

24

7070Chem1AA3

Review: Electron Configuration

Three principles/rules are used to determine the electron configuration:

Aufbau PrinciplePauli Exclusion PrincipleHund’s rule

7171Chem1AA3

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

7272Chem1AA3

Review: s-orbitals

Spherical:

Page 25: Chapter 26   skeleton notes

25

7373Chem1AA3

Review: p-orbitals

3 of them: px, py, pz

7474Chem1AA3

Example: Carbon

1s22s22p2

The outer most electrons of atoms (valence electrons) govern the chemical and physical properties

7575Chem1AA3

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

Page 26: Chapter 26   skeleton notes

26

7676Chem1AA3

Methane - CH4

• Problem: the shape of methane is tetrahedral (AX4)

• Bond angles are 109.5o not 90o

7777Chem1AA3

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

7878Chem1AA3

sp3 Hybridization (section 11-3)

1s22s22p2

Ground state4 sp3 hybrid orbitals

4 atomic orbitals

Page 27: Chapter 26   skeleton notes

27

7979Chem1AA3

sp3 Hybridization

8080Chem1AA3

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

8181Chem1AA3

Bonding-methane

Overlap of sp3 orbitals from carbon and 1s-orbitals from hydrogen

End-on (or end-to-end) overlap produces sigma (σ) bonds.

End-on overlap of sp3-orbitals also produces σ-bonds.

109.5o

Page 28: Chapter 26   skeleton notes

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8282Chem1AA3

Diagnostic iClicker Question

How many σ-bonds are there in this molecule?

(a) 1(b) 2(c) 7(d) 14

H

H

H

HH

H

PH

8383Chem1AA3

Diagnostic iClicker Question

How many sp3-orbitals are there in this molecule?

(a) 1(b) 2(c) 7(d) 8

H

H

H

HH

H

PB

8484Chem1AA3

Diagnostic iClicker Question

How many sp3-sp3 σ-bonds are there in this molecule?

(a) 1(b) 2(c) 7(d) 14

JV

Page 29: Chapter 26   skeleton notes

29

8585Chem1AA3

Diagnostic iClicker Question

How many sp3-hybridized atoms are there in this molecule?

(a) 2(b) 6(c) 8(d) 26

HS

Moving beyond alkanes:Functional Groups

8787Chem1AA3

NH2

NH

O

CO2H O

OMe

Sample Problem

What functional groups do you see?

Page 30: Chapter 26   skeleton notes

30

8888Chem1AA3

NH2

NH

O

CO2H O

OMe

Sample Problem: Solution

Carboxylic Acid

AmineAmide

Ester

Aromatic/Arene

8989Chem1AA3

Table 26.2

* Not a functional group

*

p. 1080

9090Chem1AA3

Table 26.2

R O R

O Ocarboxylic acid

anhydride H3C O CH3

O O

Page 31: Chapter 26   skeleton notes

31

9191Chem1AA3

Table 26.2

You must be able to recognize these functional groups

9292Chem1AA3

Diagnostic iClicker Question

Which functional group is not found in this molecule?

(a) aryl(b) amine(c) amide(d) phenol

PH

NH

NH2

OH

9393Chem1AA3

Diagnostic iClicker Question

Which functional group is not found in this molecule?

(a) aryl(b) hydroxyl(c) aryl halide(d) ester

PB

N OH

NH

O

F

OH OH O

Page 32: Chapter 26   skeleton notes

32

9494Chem1AA3

Diagnostic iClicker Question

Which functional group is not found in this molecule?

(a) amide(b) ketone(c) aryl halide(d) alkene

JV

NH

HN

O

O

Cl

9595Chem1AA3

Diagnostic iClicker Question

Which functional group is not found in this molecule?

(a) aryl(b) hydroxyl(c) amine(d) amide

PB

NN NH

N

O

SO O

N

NEtO

9696Chem1AA3

Synthesis

1) Functional group interconversion– ex. Converting an aldehyde to an alcohol

2) Carbon-carbon bond forming reactions– ex. Grignard reaction

H OH

O

1. CO2

2. H3O+R MgX R CO2H

Page 33: Chapter 26   skeleton notes

33

Alkenes

Section 26-3

9898Chem1AA3

Alkenes (CnH2n)

9999Chem1AA3

Multiple Covalent Bonds

• Ethylene has a double bond in its Lewis structure

• VSEPR says trigonal planar shape at C

sp2 hybridization

p. 435

Page 34: Chapter 26   skeleton notes

34

100100Chem1AA3

sp2 Hybrid Orbitals (section 11-4)

Combine one 2s orbital + two 2p orbitalsthree sp2 orbitals (+ one 2p orbital left

over)

Hybrid orbital lobes pointing in the direction of an equilateral triangle: bond angles 120o

101101Chem1AA3

sp2 Hybrid Orbitals

102102Chem1AA3

sp2 Hybrid Orbitals

• The extra p-orbital can be used to form π-bonds

• π-bonds are covalent bonds that form by the sideways overlap of parallel p-orbitals

eclipsed p-orbitalsπ-bond

staggered p-orbitalsno π-bond

Page 35: Chapter 26   skeleton notes

35

103103Chem1AA3

Ethene

Section 11-4 Overlap above and below plane of atoms gives 1 π bond

104104Chem1AA3

Recall: Conformations of alkanes

105105Chem1AA3

Alkenes have restricted rotation

Geometric Isomers

p. 1086

cis trans

Page 36: Chapter 26   skeleton notes

36

106106Chem1AA3

Fats and Oils: Triacylglycerols

O

O

O

O

R

R

O

O

R

triacylglycerol

Fat: solid at room temp.Oil: liquid at room temp.

Key Factors:• Chain length (MW)• Number of double bonds• Geometry of the double

bonds

OH

OH

OH

glycerol

(More information available on p. 1137-1139)

107107Chem1AA3

Concept Check

Which of these two fatty acids has the higher melting point and why?

RO

O

Linoleic acid (R = H)

RO

O

Stearic acid (R = H)

108108Chem1AA3

Concept Check: Solution

RO

O

Linoleic acid (R = H)

RO

O

Stearic acid (R = H)

mp = -5oC

mp = 70oC

Less efficient packing because of kink in chain geometry, therefore weaker intermolecular forces and lower melting point.

Straight chain allows more efficient packing, therefore strongerintermolecular forces and higher melting point.

Page 37: Chapter 26   skeleton notes

37

109109Chem1AA3

Impact of Geometry

110110Chem1AA3

The E,Z System of Nomenclature

• Need a new system• Higher priority higher atomic number

p. 1106

Z isomer E isomer

111111Chem1AA3

Concept Check

OMe2NOMe2N

Label the tamoxifen isomers as E or Z:

Z E

Page 38: Chapter 26   skeleton notes

38

112112Chem1AA3

Formative iClicker Question #2

Which molecule has an E configuration?

F

ClF

Cl(a) (b) (c)

(d) (e)

PH

113113Chem1AA3

Formative iClicker Question #2

Which molecule has an E configuration?

(a) (b) (c)

(d) (e)

F

FF

F

PB

114114Chem1AA3

Formative iClicker Question #2

Which molecule has an E configuration?

(a) (b) (c)

(d) (e)

Cl

ClCl

Cl

JV

Page 39: Chapter 26   skeleton notes

39

115115Chem1AA3

Formative iClicker Question #2

Which molecule has an E configuration?

Cl

ClF

Cl F(a) (b) (c)

(d) (e)

F

HS

116116Chem1AA3

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)

117117Chem1AA3

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)

Page 40: Chapter 26   skeleton notes

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118118Chem1AA3

Diagnostic iClicker Question

Which molecule has the highest degree of unsaturation?

(a) (b) (c)

PH

119119Chem1AA3

Diagnostic iClicker Question

Which molecule has the highest degree of unsaturation?

(a) (b) (c)

PB

120120Chem1AA3

Diagnostic iClicker Question

Which molecule has the lowest degree of unsaturation?

(a) (b) (c)

JV

Page 41: Chapter 26   skeleton notes

41

121121Chem1AA3

Diagnostic iClicker Question

Which molecule has the lowest degree of unsaturation?

HS

(a) (b) (c)

Reactions involving alkenes

Section 26-3

123123Chem1AA3

Addition Reactions

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.

Not observed

p. 1087-1088

Page 42: Chapter 26   skeleton notes

42

124124Chem1AA3

Explanation of Markovnikov’s rule

H Br

H

+

+

H

2o carbocation - less stable

3o carbocation - more stable

Br -

X

Br -

H

Br

haloalkane product

δ+δ-

125125Chem1AA3

Curly arrows

• The curly arrow represents electrons moving from the alkene π-bond to the proton of HBr, forming a C-H bond.

• We will examine this in more detail in nucleophilic substitution reactions (Section 26-11)

H Brδ+δ-

126126Chem1AA3

Carbocation stability

Stability:

Why do alkyl substituents increase cation stability?

Steric:

The cationic carbon rehybridizes from sp3 to sp2, relieving the steric clash between substituents

H3C+ < < <

methyl 1° 2° 3°< < <

Br

H3CH3C CH3

Br -

CH3H3C

H3C

Page 43: Chapter 26   skeleton notes

43

127127Chem1AA3

Carbocation stability

Why do alkyl substituents increase cation stability?

Electronic:

Alkyl substituents are electron donating compared with H. Donating electrons to an electron deficient (positively charged) centre stabilizes it.

= a permanent electric dipole

CH3

CH3H3C

δ-δ+

128128Chem1AA3

Formative iClicker Question #3

What is the expected product, according to Markovnikov's rule?

HBr

(a)

Br

BrBr

(b)

(c)

Br

(d)

Br

PH

129129Chem1AA3

Formative iClicker Question #3

What is the expected product, according to Markovnikov's rule?

HI

(a)

I

II

(b)

(c) (d)

I

I

PB

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130130Chem1AA3

Formative iClicker Question #3

What is the expected product, according to Markovnikov's rule?

HBr

(a)BrBr

(b)

(c) (d)

Br Br

JV

131131Chem1AA3

Formative iClicker Question #3

What is the expected product, according to Markovnikov's rule?

HCl

(a)

Cl

ClCl

(b)

(c) (d)

Cl

Cl

HS

132132Chem1AA3

Hydration Reaction

• Addition is favoured (forward reaction) in dilute acid

• Elimination is favoured (reverse reaction) in concentrated acid

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133133Chem1AA3

Hydration also follows Markovnikov's rule

HO

HH2O

H

+H2O

H3O+

H

+OH

H

OH

H

H

HO

H3O+

JV?

134134Chem1AA3

Reduction of Alkenes

HH

H H

catalyst

Hydrogenation

135135Chem1AA3

Application: Hydrogenation of Natural Products

CH2OC(CH2)7CH

CHOC(CH2)7CH

O

CH(CH2)7CH3

CH(CH2)7CH3

O

CH2OC(CH2)7CH

O

CH(CH2)7CH3

3H2

Ni catalyst heat

CH2OC(CH2)16CH3

CHOC(CH2)16CH3

O

O

CH2OC(CH2)16CH3

O

Unsaturated vegetable oil(olein-liquid)

Solid cooking fat-shortening (stearin, solid)

(More information available on p. 1137-1139)

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136136Chem1AA3

Partial Hydrogenation

RO

O

RO

O

H2 (1 equiv.)

catalyst

H

Hmixture

saturated at either double bond, e.g.

137137Chem1AA3

cis versus trans fatty acids

cis-9-octadecenoic acid(Oleic acid)

trans-9-octadecenoic acid(Elaidic acid)

Alkynes

Section 26-3

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139139Chem1AA3

Alkynes

According to VSEPR, alkynes are linear

p. 1085

140140Chem1AA3

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

sp hybridization

141141Chem1AA3

sp Hybrid Orbitals

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142142Chem1AA3

Acetylene: Orbitals

• Acetylene, C2H2, has a triple bond.• Linear at carbon

Reactions of Alkynes

144144Chem1AA3

Reduction of Alkenes and Alkynes

HH

H H

catalyst

CH3CH2C CCH3 + H2

CH3

HH

EtLindlar's catalyst

CH3CH2C CCH3 + H2Pd/C

CH3CH2CH2CH2CH3

Cis isomer only!

p. 1088

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49

The Carbonyl Group:ketones and aldehydes

Section 26-6

146146Chem1AA3

Examples

Ketones

Aldehydes

O

Acetone Methyl ethyl ketone (MEK) Testosterone

O

OHCH3

H3C

O

H

O

H

O

H H

O

Formaldehyde Benzaldehyde Cinnamaldehyde

p. 1094-1095

147147Chem1AA3

Structure and Polarity

H3C CH3

O122o

116o

122o

H CH3

O124o

118o

118o

H H

O121o

118o

121o

R R

Oδ+

δ-

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50

Synthesis and reactions of aldehydes and ketones

Section 26-5, 26-6

149149Chem1AA3

Synthesis

Oxidation of alcohols:

HOH

O

OH O

Oxidation: Addition of an oxygen atom or removal of (a molecule of) hydrogen

[O] = Oxidizing agent

[O]

[O]

150150Chem1AA3

Primary, Secondary & Tertiary Alcohols

R CH2 OH

R CH OHR'

R C OHR'

R''

Primary (1o)

Secondary (2o)

Tertiary (3o)

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151151Chem1AA3

Oxidation

• Primary alcohol aldehyde carboxylic acid

• Secondary alcohol ketone

• Tertiary alcohol no reaction– a C-C bond would have to break in order for oxidation

to occur

HOH

O

OH

O

OH O

152152Chem1AA3

Formative iClicker Question #4

What is the expected product of oxidation of 2,2-dimethylpropanol?

(a) 2,2-dimethylpropanoic acid(b) 2,2-dimethylpropanone(c) 2-methyl-2-propanal(d) no reaction

PH

153153Chem1AA3

Formative iClicker Question #4

What is the expected product of oxidation of s-pentanol?

(a) methyl butyl ketone(b) 2-pentanone(c) pentanoic acid(d) none of the above

PB

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154154Chem1AA3

Formative iClicker Question #4

What is the expected product of oxidation of isopentanol?

(a) methyl butyl ketone(b) 2-pentanone(c) 4-methyl pentanoic acid(d) none of the above

JV

155155Chem1AA3

Formative iClicker Question #4

What is the expected product of oxidation of 2-methylbutanol?

(a) 2-methylbutanoic acid(b) 2-methylbutanone(c) s-pentanoic acid(d) none of the above

HS

156156Chem1AA3

Oxidizing Agents

• Commonly metals in high oxidation states (transfer of 2 to 4 electrons)

e.g., MnO4-, Cr2O7

2- (KMnO4, K2Cr2O7)

• Usually done in acid or base to facilitate electron transfer

• Pyridinium chlorochromate (PCC)– Specific for oxidizing 1o alcohols aldehydes

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157157Chem1AA3

Metabolism of Alcohol: Detoxification

ethanol rapidly distributes from blood to tissues/organs brain

two-step oxidation of ethanol acetaldehyde acetic acid

acetic acid is eliminated by kidneys or metabolized into energy

Enzymatic Detoxification by Two-step Oxidation

"One of the disadvantages of wine is that it makes a man mistake words for thoughts." -- Samuel Johnson

158158Chem1AA3

Metabolism of Alcohol: Detoxification

Enzymatic Detoxification by Two-step Oxidation

Alcohol Dehydrogenase

AcetaldehydeDehydrogenase

OH + NAD+

H

O+ NADH + H+

+ NAD+ + NADH + H+

OH

O

H

O

oxidizing agent toxic intermediate

non-toxic final product

159159Chem1AA3

Addition Reactions to the Carbonyl Group

Reduction: NaBH4 is a source of H- (hydride)

H OH

O 1. NaBH4

2. H3O+

O 1. NaBH4

2. H3O+

OH

aldehyde 1o alcohol

2o alcoholketone

p. 1096

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54

Synthesis and Reactions of Carboxylic Acids and

Derivatives

Section 26-7

161161Chem1AA3

Examples

p. 1097

162162Chem1AA3

Carboxylic Acid: Structure

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55

Synthesis and Reactivity

Section 26-7

164164Chem1AA3

Carboxylic acids

Weak acids:

OH

O

O-

O+ H3O++ H2O Ka = 1.4x10−5

OH

O

O-

O+ H3O++ H2ONaOH Na+ + H2O

R Cl

O

R O

O

R R NHR

O

R O

O

R

O

Acid chloride Ester AmideAnhydride

Derivatives:

165165Chem1AA3

Preparation of Esters

OH

O

OCH2CH3

OH++ CH3CH2OH + H2O

• Fischer Esterification

• Acid catalyst

• Condensation reaction

p. 1098

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166166Chem1AA3

Hydrolysis of Esters

OH

O

OCH2CH3

O H++ CH3CH2OH+ H2O

• Reverse of previous reaction

• Also requires acid catalyst

167167Chem1AA3

Acid chlorides

Acid chloride

R Cl

O

R NH

OR NH2 R

+ HCl+

R Cl

O

R O

OR OH

R+ HCl+

R OH

O R NH2

R O-

O

RH3N+Carboxylic acid Acid-base

reaction

amide

ester

168168Chem1AA3

Acetyl Group

p. 1097

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57

Synthesis

Section 26-12

170170Chem1AA3

Concept Check: Synthesis

Fill in the missing reagents:

OHO

171171Chem1AA3

Concept Check: Solution

OHO 1. NaBH4

2. H3O+

conc. H2SO4, ∆

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172172Chem1AA3

Formative iClicker Question #4

What are conditions i and ii?

O

OHi

ii

PH

PCCNaBH4(d)KMnO4NaBH4(c)

10% H2SO4PCC(b)KMnO4Lindlar's catalyst(a)

iii

173173Chem1AA3

Formative iClicker Question #4

What are conditions i and ii?OH

i

ii

PB

10% H2SO4conc. H2SO4(d)H2/Pd-C10% H2SO4(c)

10% H2SO4PCC(b)conc. H2SO410% H2SO4(a)

iii

174174Chem1AA3

Formative iClicker Question #4

What are conditions i and ii?

Cl

i ii

JV

HClLindlar's catalyst(d)

Cl2H2/Pd-C(c)

HClH2/Pd-C(b)

Cl2PCC(a)

iii

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175175Chem1AA3

Formative iClicker Question #4

What are conditions i and ii?i ii

HS

H2/PdLindlar's catalyst(d)

Lindlar's catalystH2/Pd-C(c)

PCCKMnO4(b)

PCCH2/Pd-C(a)

iii

Substitution Reactions and Mechanisms

Section 26-11

177177Chem1AA3

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-)

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178178Chem1AA3

Chemical Reactions Continued

• The reagent does not necessarily need to be charged: Lone electron pairs would also be attracted to a dipole

179179Chem1AA3

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

180180Chem1AA3

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

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181181Chem1AA3

Substitution Reactions at sp3 Hybridized Carbon

Charged nucleophiles

Neutral nucleophiles

182182Chem1AA3

Mechanism

• The flow of electrons between a nucleophile and electrophile can be represented by a double-headed curly arrow

• The result of the movement is to form a bond between an electrophile and a nucleophile

NH3 E+

NH3 E+ N EH

HH

+

183183Chem1AA3

Mechanism (continued)

• The arrow tail starts at the source of the moving electrons and the arrow head indicates its final destination

NH3 E+

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184184Chem1AA3

SN2 Mechanism

Rate = k[OH-][CH3Cl]

S = substitution; N = nucleophilic, 2 = bimolecular

p. 1111

185185Chem1AA3

Diagnostic iClicker Question

Cl- + CH3Br CH3Cl + Br-

CH3ClBr-(d)

Br-Cl-(c)

Cl-CH3Br(b)

CH3BrCl-(a)

ElectrophileNucleophile

PH

What are the nucleophile and the electrophile in this reaction?

186186Chem1AA3

PB

Diagnostic iClicker Question

H3C-NH2 + CH3Cl H3C-NH-CH3 + HCl

H+Cl-(d)

Cl-CH3NH2(c)

CH3ClCH3NH2(b)

H3C-NH-CH3CH3Cl(a)

ElectrophileNucleophile

What are the nucleophile and the electrophile in this reaction?

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187187Chem1AA3

JV

Diagnostic iClicker Question

What are the nucleophile and the electrophile in this reaction?

H3C-NH2 + CH3Cl H3C-NH-CH3 + HCl

H+H3C-NH-CH3(d)

CH3ClCH3NH2(c)

Cl-CH3Cl(b)

H3C-NH-CH3CH3NH2(a)

ElectrophileNucleophile

188188Chem1AA3

HS

Diagnostic iClicker Question

What are the nucleophile and the electrophile in this reaction?

Cl-Br-(d)

CH3ClCl-(c)

Cl-CH3Cl(b)

Br-Cl-(a)

ElectrophileNucleophile

Cl- + CH3Br CH3Cl + Br-

189189Chem1AA3

SN2 Mechanism

More on mechanisms in the next section

δ- δ-

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190190Chem1AA3

SN2: Inversion of Configuration

191191Chem1AA3

SN1 Mechanism (unimolecular)

p. 1112

192192Chem1AA3

SN1 Mechanism

Rate = k [(CH3)3CBr]slow

fast

fast

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193193Chem1AA3

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

194194Chem1AA3

Formative iClicker Question #5

Rank the likelihood of the following compounds to undergo SN2 nucleophilic substitutions:

(a) i < ii ≈ iii (b) i > ii > iii (c) i > ii ≈ iii(d) i ≈ ii > iii

ClCl

Cl

i ii iii

PH

195195Chem1AA3

Formative iClicker Question #5

Rank the likelihood of the following compounds to undergo SN2 nucleophilic substitutions:

(a) iii ≈ ii < i (b) i ≈ ii > iii(c) i > iii > ii(d) ii > i < iii

Cl ClCl

i ii iii

PB

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196196Chem1AA3

Formative iClicker Question #5

Rank the likelihood of the following compounds to undergo SN2 nucleophilic substitutions:

(a) iii ≈ ii > i (b) i ≈ ii > iii(c) i > ii ≈ iii(d) ii > i < iii

ClCl

Cl

i ii iii

JV

197197Chem1AA3

Formative iClicker Question #5

Rank the likelihood of the following compounds to undergo SN2 nucleophilic substitutions:

(a) i ≈ iii < ii (b) i ≈ ii < iii(c) i < ii > iii(d) ii ≈ i > iii

Cl

Cl Cl

i ii iii

HS