Université McGill

1

Tim Berners-Lee

Université McGill

VISUELVISUEL

CLIPS SONORESCLIPS SONORES

FORMAT DES FORMAT DES PRÉSENTATIONS PRÉSENTATIONS

DÉMONSTRATIONSDÉMONSTRATIONS

EXEMPLES PERTINENTSEXEMPLES PERTINENTS

SUPPORTS PÉDAGOGIQUESSUPPORTS PÉDAGOGIQUES

VISUELVISUEL






200 DIAPOSITIVES200 DIAPOSITIVESCOURS DE 75 MINUTESCOURS DE 75 MINUTES

VISUELVISUEL






2

ΔE = Δm x c2

1905

VISUELVISUEL






TRANSITIONSTRANSITIONSÉLECTRONIQUESÉLECTRONIQUES

VISUELVISUEL






LE PRINCIPELE PRINCIPEDE LEDE LEDE LEDE LE

CHATELIERCHATELIER

3

Ca5(PO4)3OH

ApatiteApatite

5 Ca+2 + 3 PO4-3 + OH-

Ca5(PO4)3OH

ApatiteApatite

5 Ca+2 + 3 PO4-3 + OH+ OH-- + H+ H++

Ca5(PO4)3OH

ApatiteApatite

5 Ca+2 + 3 PO4-3 + OHOH-- + H+ H++

HH22OO

Ca5(PO4)3OH

ApatiteApatite

HH22OO

5 Ca+2 + 3 PO4-3 + OHOH-- + H+ H++

CHFBrCl

REPRÉSENTATIONS DE CRAM

CHFBrClCHFBrCl

4

CHFBrCl

REPRÉSENTATIONS DE CRAM

STÉRÉOISOMÈRESMolécules où les atomes ont la même connectivité mais différentes organisations spatiales

ISOMÈRES DE CONSTITUTION (STRUCTURE)

Molécules ou les atomes la même formule brute mais différentes connectivités

Molécules ou les atomes la même formule brute mais différentes connectivités

ISOMÈRES DE CONSTITUTION (STRUCTURE)

5

H

CH3

CH3

H

HO

H

H

AndrostenolAndrostenol

VISUELVISUEL






General ChemistryPrinciples and Modern Applications

Petrucci et al. 10th Edition$169.95

6

Exercices

eBook: Version électronique

Téléchargées avant le cours

7

Cours LC 101Jussieu

Ariel Fenster

http://www.lcpmr.upmc.fr

www.cool.mcgill.cawww.cool.mcgill.caCOOLCOOL

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iPod

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STUDENT RESPONSE SYSTEM "Clickers"STUDENT RESPONSE SYSTEM "Clickers"

Lequel de ces scientifiques n'a pas Lequel de ces scientifiques n'a pas reçu le prix Nobelreçu le prix Nobel ??

1. Ernest Rutherford

44 E

rnes

t Rut

herf.

..

Niel

s Boh

r

Dim

itri M

ende

...

Mari

e Cur

ie

Linu

s Pau

ling

0% 0% 0%0%0%

:05

2. Niels Bohr3. Dimitri Mendeleïev4. Marie Curie5. Linus Pauling

Quelle relation existeQuelle relation existe--tt--il entre ces deux il entre ces deux structures?structures?

45 Isom

ères d

e cons

tit...

Stér

éoiso

mèr

es

Iden

tiques

Auc

une i

dée

0% 0%0%0%

:05

1. Isomères de constitution

2. Stéréoisomères3. Identiques4. Aucune idée

ariel fenster@mcgill caoss.mcgill.ca

cool.mcgill.ca

[email protected]

GENERAL CHEMISTRYCHEM-110

LEWIS STRUCTURES

Lewis SymbolsChemical Symbol nucleus

Dots valence electrons

Si

9

Octet Rule

Atoms surround themselves with eight electrons to achieve noble

t bilitgas stability

Al2O3 Al2O3

WRITING LEWIS STRUCTURES

1. Count total # of valence e-

For +ve charge remove e-For +ve charge, remove e

For –ve charge, add e-

10

2. Draw a plausible skeleton

Symmetrical structures arepreferred

Least electronegative element usually in centre

3. Achieve an octet around each atom

Convert lone pairs into double or triple bonds, if necessary

NO3-

N 5 valence e- x 1 = 5O 6 valence e- x 3 = 18

1 (-)+

24 e-

NO3-

NO3- NO3

-

11

NO3-

CH3NCO

H H?..

CN

CH

H

H

O

CN

CH

H

H

OC

NC

H

H

H

O?....

..

......

..

..

Tells us where electrons are located.

Formal Charges

Helps us predict the most plausible structure.

Tells us where electrons are located

Formal Charges

F.C. = # of valence e- – # of l.p. e-

– ½ # of bonding e-

N O

+

....

NO+

F.C. (N) = 5 – 2 – ½ 6= 0

F.C. (O) = 6 – 2 – ½ 6= +1

N O

+

....

NO+

Note: F.C. (N) + F.C. (O) = +1

The sum of the formal charges must be equal to overall charge of the species

12

RESONANCE FORMS

Several Lewis structures can be written but the “true” one is awritten, but the “true” one is a hybrid

RESONANCE FORMS

Resonance forms have the same connectivity but different electronconnectivity but different electron distribution

O3

Determining the "best"Resonance form

1. When writing resonance structures the connectivity cannot be altered (only lone pair electrons and electrons in double and triple multiple bond can be moved).

f

Writing resonance structures

2. A structure with the lowest magnitudes of formal charges is preferred (greater contribution to the hybrid).

3. A structure with a negative charge on the most electronegative atom is preferred.

N2O

13

Consider of the four forms that can be Consider of the four forms that can be written for Nwritten for N2200

What is the relationship between structure What is the relationship between structure 1 and 4 ?1 and 4 ?

Res

onance

form

...

Iden

tical

Structu

ral is

o...

0% 0%0%

:05

1.1. Resonance Resonance formsforms

2.2. IdenticalIdentical3.3. Structural Structural

isomersisomers

STRUCTURAL ISOMERS

Structural isomers have the same molecular formula but differentmolecular formula but different connectivities

What is the relationship between structure What is the relationship between structure 1,2 and 3 ?1,2 and 3 ?

Res

onance

form

...

Iden

tical

Structu

ral is

o...

0% 0%0%

:05

1.1. Resonance Resonance formsforms

2.2. IdenticalIdentical3.3. Structural Structural

isomersisomers

RESONANCE FORMS

Resonance forms have the same connectivity but different electronconnectivity but different electron distribution

N2O

-1-1+1 +10 0

-1 -1+1+1 +2-2

14

Which of the four forms that can be written Which of the four forms that can be written for Nfor N220 is (are) the most plausible0 is (are) the most plausible

1.1. (1)(1)

2.2. (2)(2)

-1 -2 -3 -4

0% 0%0%0%

:05

3.3. (3)(3)

4.4. (4)(4)

N2O

-1-1+1 +10 0

BEST

-1 -1+1+1 +2-2

H H..

Which of the structures Which of the structures best best represent represent methyl methyl isocyanateisocyanate

CN

CH

H

H

O

CN

CH

H

H

OC

NC

H

H

H

O....

..

..

..

..

..

..0

0

000

0

0

0

-1

-1+1

+1

AC

B

Which of the structures Which of the structures best best represent represent methyl methyl isocyanateisocyanate

1.1. AA

2.2. BB

A B C All

0% 0%0%0%

:05..

2.2. BB

3.3. CC

4.4. AllAll

CH3NCO

H H..

CN

CH

H

H

O

CN

CH

H

H

OC

NC

H

H

H

O....

..

..

..

..

..

..0

0

000

0

0

0

-1

-1+1

+1

BEST

Exceptions to the Octet Rule

1. Incomplete Octet

15

F B F

BF3

.... ....

..

..

F B FF

6 e-

.. ....

F B F

BF3

.... ....0

00

..

..F B F

F

6 e-

.. ....0

BETTER!


1. Incomplete Octet

2 E d d O t t2. Expanded Octet

SO42-

SO42-

BETTER!


1. Incomplete Octet

2 E d d O t t2. Expanded Octet

3. Paramagnetic Species

16

NO NO

Odd # of electrons


V.S.E.P.R.

VSEPR Theory

• Molecules adopt the geometry which maximizes the distance between electron pairs around abetween electron pairs around a central atom, and thus minimizes electrostatic repulsions.

VSEPR Theory

Molecular shape depends on:

• The number of electron pairs

• The type of electron pairs

17

VSEPR

Molecules containing only bonding pairs around the central atom

The shape depends only on the number of electron pairs

2 e- pairs

Linear

Formula: AB2

Bond Angle: 180°

2 e- pairs Linear

Example: BeI2

1800

2 e- pairs

Linear3 e- pairs

Trigonal

Formula: AB3

Bond Angle: 120°

3 e- pairs

Trigonal

Example: BF3

1200

2 e- pairs

Linear4 e- pairs

Tetrahedral3 e- pairs

Trigonal

18

4 e- pairs

Tetrahedral

Formula: AB4

Bond Angle: 109.5°Example: CH4 109.50

2 e- pairs

Linear4 e- pairs


Trigonal

5 e- pairs

Trigonal bipyramidal

5 e- pairs


Formula: AB5

Bond Angle: 90°, 120°Example: PF5

1200

900

2 e- pairs

Linear4 e- pairs


Trigonal

5 e- pairs

Trigonal bipyramidal6 e- pairs

Octahedral

6 e- pairs

O t h d l

Formula: AB6

Bond Angle: 90°Example: SF6

Octahedral900

900

VSEPR Examples

Predict the geometry of the following molecules

19

BeCl2

Lewis Structure::

:

:

:

:

: BeCl

Cl

What is the molecular geometry of BeClWhat is the molecular geometry of BeCl22??

1.1. LinearLinear2.2. Trigonal planar Trigonal planar 33 TetrahedralTetrahedral

Linear

Trigon

al plan

ar

Tetrah

edral

Trigon

al bipyra

midal

Octa

hedral

0% 0% 0%0%0%

:05

3.3. TetrahedralTetrahedral4.4. Trigonal bipyramidalTrigonal bipyramidal5.5. OctahedralOctahedral

BeCl2

Lewis Structure::

:

:

:

:

: BeCl

Cl

Two electron pairs around Be

Linear molecule

Lewis Structure:N

+

NH4+

What is the molecular geometry of NHWhat is the molecular geometry of NH44++??

1.1. LinearLinear2.2. Trigonal planar Trigonal planar 33 TetrahedralTetrahedral

Linear

Trigon

al plan

ar

Tetrah

edral

Trigon

al bipyra

midal

Octa

hedral

0% 0% 0%0%0%

:05

3.3. TetrahedralTetrahedral4.4. Trigonal bipyramidalTrigonal bipyramidal5.5. OctahedralOctahedral

N

+

NH4+

Lewis Structure:

Four electron pairs around N

Tetrahedral molecule

20

NH4+

Tetrahedral molecule

SF6

Lewis Structure: SF

FF F

FF

: : :

:

:

:

:::

:: :

::

::

:

:

48 e-

What is the molecular geometry of SFWhat is the molecular geometry of SF66??

1.1. LinearLinear2.2. TrigonalTrigonal planar planar 33 TetrahedralTetrahedral

Linear

Trigon

al plan

ar

Tetrah

edral

Trigon

al bipyra

midal

Octa

hedral

0% 0% 0%0%0%

:05

3.3. TetrahedralTetrahedral4.4. TrigonalTrigonal bipyramidalbipyramidal5.5. OctahedralOctahedral

SF6

Lewis Structure: SF

FF F

FF

: : :

:

:

:

:::

:: :

::

::

:

:

48 e-

Six electron pairs around S

Octahedral molecule

SF6

Octahedral molecule

VSEPR

molecules containing both, bonding and lone pairs, around the central atom

The shape depends on the respective number of pairs and their position

21

Lone pairs (l.p.) are not as localized as bonding pairs (b.p.), and thus cause stronger repulsions


VSEPR Lone Pair Examples

Predict the geometry of the following molecules

22

O....

HHLewis Structure:

H2O

Bonding Pairs: 2Lone Pairs: 2+

4

electron pairs geometry: tetrahedral

H2O

What is the molecular geometry of HWhat is the molecular geometry of H22O?O?

1.1. LinearLinear2.2. Bent Bent 33 PyramidalPyramidal

Linear

Ben

t

Pyramidal

T-Shap

ed

See-sa

w

Square plan

ar

0% 0% 0%0%0%0%

:05

3.3. PyramidalPyramidal4.4. TT--ShapedShaped5.5. SeeSee--sawsaw6.6. Square planarSquare planar

BrF4+ 34 e-

Lewis Structure:

..

+.

..F

..

.... ..

....

.F

FBr

..

.. ....F

BrF4+ 34 e-

Lewis Structure: +

FF

FBr....BrF +

FF

Bonding Pairs: 4Lone Pairs: 1+

5

23

BrF4+ 34 e-

electron pairs geometry: trigonal bipyramidal

BrF4+ 34 e-

molecular geometry:


Br

+

Br

+

see-saw trigonal pyramidal

90o lp-bp 90o lp-bp

2 3

BrF4+ 34 e-

molecular geometry: see-saw


Br

+

22 e-

Lewis Structure:

XeF2

XeF ... .....

.. F.........

What is the molecular geometry of XeFWhat is the molecular geometry of XeF22??

1.1. LinearLinear2.2. TrigonalTrigonal planar planar 33 TetrahedralTetrahedral

Linear

Trigon

al plan

ar

Tetrah

edral

Trigon

al bipyra

midal

Octa

hedral

0% 0% 0%0%0%

:05

3.3. TetrahedralTetrahedral4.4. TrigonalTrigonal bipyramidalbipyramidal5.5. OctahedralOctahedral

22 e-

Lewis Structure: XeF ... .....

.. F.........

XeF2

Bonding Pairs: 2

Lone Pairs: 3+5

24

22 e-

electron pairs geometry: trigonal bipyramidalXeF2 22 e-


molecular geometry: linear

XeF2

22 e-


molecular geometry: linear

XeF2

Molecules and Ions containing Multiple Bondsp

For geometrical considerations, a multiple bond can be treated as if it pwere a single bond

CH3NCO

Recall

25

CH3NCO

Recall e- groups: 4

e- geometry:e geometry:tetrahedral

molecular geometry:

tetrahedral

Angle: ~109.5°

CH3NCO

Recall

CH3NCO

Recalle- groups: 3

CH3NCO

Recalle- groups: 3

Moleculargeometry: bent

Angle: ~120°

CH3NCO

Recall

CH3NCO

Recalle- groups: 2

26

CH3NCO

Recalle- groups: 2

e- geometry:linear

moleculargeometry: linear

Angle: ~180°

CH3NCO


VALENCE BOND THEORY

Valence Bond Theory

The covalent bond results from the l f t i bit l t i ioverlap of atomic orbitals containing

one unpaired electron each

Hydrogen H2

1sH

1sH

27

Covalent Bond

• The electrons are no longer confined to a single s orbital around one atomone atom.

• Instead, they can move over both orbitals for the entire molecule.

Covalent Bond

• The electrons are no longer confined to a single s orbital around one atomone atom.

• Instead, they can move over both orbitals for the entire molecule.

GREATER STABILITY!

Valence Bond Theory Examplesp

1sH

Hydrogen H2

1sHs-s overlap

1sH

Hydrogen H2

1sHs-s overlap

1sH

Hydrogen H2

1sHs-s overlap

σ bond

28

F

Fluorine F2

p1s 2s 2p

1s 2s 2pF

p-p overlap

p

p-p head to head overlap

x

σ bond


Does diatomic helium HeDoes diatomic helium He22 exist?exist?

1.1. YesYes2.2. NoNo33 No IdeaNo Idea

Yes No

No Id

ea

0% 0%0%

:05

3.3. No IdeaNo Idea

Helium

He 1s

He 1sHe 1s

Helium

He 1s

He 1sHe 1s

Filled orbital ∴ no possible overlap

He2

X

29

Multiple Bonds

In OIn O2 2 the atoms are linked athe atoms are linked a ??

1.1. Single bond Single bond 2.2. Double bondDouble bond33 TrripleTrriple bondbond

Single

bond

Double

bond

Trriple

bond

No id

ea

0% 0%0%0%

:05

3.3. TrripleTrriple bond bond 4.4. No ideaNo idea

1 double covalent bond

Oxygen

.O. . . O .. ..

Oxygen

O1s 2s 2p

1s 2s 2pO

x

px px


x

σ bond


O O

30

Oxygen

O

1 σ bond

1s 2s 2p

1s 2s 2pO

y y

py py

p-p side to side overlap

y

p-p side to side overlap p-p side to side overlap

x

Overlap above and belowthe bond axis


π bond

Oxygen

O

1 σ bond

1s 2s 2p

1s 2s 2pO

1 π bond

31

Double Bond

1 σ bond

Maximum electron density along the the bond axis

In NIn N2 2 the atoms are linked athe atoms are linked a ??

1.1. Single bond Single bond 2.2. Double bondDouble bond33 Triple bondTriple bond

Single

bond

Double

bond

Triple

bond

No id

ea

0% 0%0%0%

:05

3.3. Triple bond Triple bond 4.4. No ideaNo idea

1 triple covalent bond

Nitrogen

..N N..

Nitrogen

N1s 2s 2p

1s 2s 2pN

x

σ bond


N N

Nitrogen

N

1 σ bond

1s 2s 2p

1s 2s 2pN

32

Nitrogen

N

1 σ bond

1s 2s 2p

1s 2s 2pN

2 π bonds p-p side to side overlap

zVertical plane

x



π bond

x


yHorizontal plane

π bond

Nitrogen

N

1 σ bond

1s 2s 2p

1s 2s 2pN

2 π bonds

Summary

Single bonds: Always σ

s-s overlap

p-p overlap head to head

s-p overlap head to head

33

Summary

Double bonds: 1 σ + 1 π

Single bonds: Always σ

Double bonds: 1 σ 1 π

Triple bonds: 1 σ + 2 π

Summary

π bonds

Only after σ bondsOnly after σ bonds

Summary

π bonds

Only after σ bondsOnly after σ bonds

Only from p-p side to side overlap

Which one of the following best describes Which one of the following best describes the bonding in hydrogen cyanide, HCNthe bonding in hydrogen cyanide, HCN

1. 1σ and 1 1 π bond

2 2 d 11 b d

0% 0% 0%0%0%

:05

2. 2σ and 1 1 π bond

3.3. 2 2 σ, 1 1 π bond and 1 lone pair

4.4. 2 2 σ, 2 2 π bond and 1 lone pair

5.5. 2 2 σ, 1 π bond and 2 lone i

Describe the bonding in HCN

C NH .C N.H

2 σ bonds2 π bonds

..

1 lone pair198

STEREOCHEMISTRY

34

Same molecular formulas but different connectivity.

STRUCTURAL ISOMERSSame molecular formulas but different connectivity.

STRUCTURAL ISOMERS

CCl2 CH2 CHCl CHCl1,1-dichloroethene 1,2-dichloroethene

C2H2Cl2

Same molecular formulas but different connectivity.

STRUCTURAL ISOMERS

STEREOISOMERS

Same molecular formulas and same connectivity but different orientation in space.

What is the relation between these two What is the relation between these two compounds?compounds?

C CHH

Cl ClC C

Cl

Cl

H

H

1.1. IdenticalIdentical

Iden

tical

Con

stitut

ional is

omer

s

Ster

eoiso

mers

Stru

ctur

al iso

mer

s

0% 0%0%0%

:05

2.2. Constitutional isomersConstitutional isomers

3.3. StereoisomersStereoisomers

4.4. Structural isomersStructural isomers

STEREOISOMERSCHCl CHCl

1,2-dichloroethene

C CHH

Cl ClC C

Cl

Cl

H

H

cis-1,2-dichloroethene trans-1,2-dichloroethene

STEREOISOMERS

CONFORMERS: stereoisomers resulting from free rotation (or a flip) around carbon-carbon bonds.

ENANTIOMERS: stereoisomers that are mirror

DIASTEREOMERS: stereoisomers that do not result from free rotation and are not mirror image of another.

ENANTIOMERS: stereoisomers that are mirror image of one another.

35

STEREOISOMERS





ETHANE

STAGGERED

Newman Projection

36

STAGGERED

ECLIPSED

STEREOISOMERS





37

STEROISOMERS STEROISOMERS

ENANTIOMERS: NON-SUPERIMPOSABLE MIRROR IMAGES

38

STEREOISOMERS





STEREOISOMERS

DIASTEREOMERS

C CHH

Cl ClC C

Cl

Cl

H

H

cis-1,2-dichloroethene trans-1,2-dichloroethene


C

CH3

HCl

ClC

CH3

HCl

Cl


Iden

tical

0% 0% 0%0%0%


3.3. ConformersConformers

4.4. DiastereomersDiastereomers

5.5. EnantiomersEnantiomers5


C

CH3

HBr Cl

C

CH3

HBrCl


Iden

tical

Con

stitut

ional is

omer

s

Con

form

ers

Dias

tereo

mer

s

Ena

ntiom

ers

0% 0% 0%0%0%




5.5. EnantiomersEnantiomers5


CH3

CH3

CH3

CH3


Iden

tical

Con

stitut

ional is

omer

s

Con

form

ers

Dias

tereo

mer

s

Ena

ntiom

ers

0% 0% 0%0%0%

:05




5.5. EnantiomersEnantiomers

O

CCH2CH3

Carvone

39

O O

C

CH2CH3

C

H2C CH3

d- carvone l- carvone

d-carvone d-carvonel-carvone

R/S Convention

Cahn - Ingold - Prelog

RULES1. Assign priority to the 4 groups attached.

This is based on atomic NUMBER of the atom.

40

1. Assign priority to the 4 groups attached. This is based on atomic NUMBER of the atom.

2 Visualize the molecule with the

RULES

2. Visualize the molecule with the LOWEST priority group AWAY from you.

1. Assign priority to the 4 groups attached. This is based on atomic NUMBER of the atom.

2 Visualize the molecule with the

RULES

2. Visualize the molecule with the LOWEST priority group AWAY from you.

3. Trace Clockwise orCounterclockwise.

RULES1. Assign priority to the 4 groups attached.


2 Visualize the molecule with the2. Visualize the molecule with the LOWEST priority group AWAY from you.

3. Trace Clockwise orCounterclockwise.

41

HIGHEST ATOMIC #

NEXTHIGHEST ATOMIC # highest atomic #

next

42

R R

RECTUS = RIGHT

S S

SINISTER = LEFT

43

R/S

Rules1. Assign priority to the 4 groups attached.



The absolute configuration for the structure The absolute configuration for the structure below isbelow is

R S

Neit

her

0% 0%0%

5

1. R

2. S

3. Neither

Rules1. Assign priority to the 4 groups attached.



Double or triple bonds are evaluated as – C holding 2, 3 carbons (Solomons p 192)

C C

H H

H

C C

H H

C

HC

Double or triple bonds are evaluated as – C holding 2, 3 carbons (Solomons p 205)

H HC

44

C

H

O C

H

O

O C

Same for other species

The absolute configuration for the structure The absolute configuration for the structure below isbelow is

C

CH3

H

CH CH2Cl

R S

0%0%

5

1. R

2. S

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