Peter Steel s ENCH241 Part1-1

8/6/2019 Peter Steel s ENCH241 Part1-1

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ENCH 241 2011Post earthquake

Peter Steel Chemistry Dept Room 650

e-mail: [email protected]


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Hands up anyone who has

not done CHEM112

(or CHEM115)


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Drawing Organic Molecules:

C C

H

H

H

H

H

H

C C

H

H

H

H

C C HH

et e et ene et ne

f r rdinate3 tetrahedral C

three rdinate 2 trig nal C

tw rdinatelinearC


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Drawing Organic Molecules

C

CN C

O

C

C

C

H HH

H

HH

H H

H

HOH

HH

Leucine(natural amino aci )

Note number of bon s to each atom type


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H2

H

O

Si liH2

H

H2

O

CH

CH3

H3C

O

H


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HN

N

N

N

N N

N

O

O

AcO

O

AcO

N


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Drawing Organic Molecules in 3D


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Drawing Organic Molecules in 3D

H NOH

O

Stereo enic centre

H N OH

O

H N OH

O

H H

Natural Unnatural

Enantiomers


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Viewing Organic Molecules in 3D

Fischer Projection


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Newman Projection


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Newman Projection


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Other Representations

Stick Dia ram

NH

Ca r lactam


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Other Representations

Ball an Stick Space Fillin


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Conformational analysis

Rotation about C C bonds

octane

cyclohexane

BUT what are their real hapes?


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Conformational analysis:

Rotation about C C bonds

These are all octane but have ifferent CONFORMATIONS


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Conformational analysis:Rotation about C C bonds

Ethane Conformers

Sta ere Eclipse

?


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Click the link belo to see an animation of therotation about the central bon of ethane

http:// .learnerstv.com/animation/animation.php ani=5 &cat=chemistry

chemistry animations


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From Bro n


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Conformational analysisRotation about C C bonds

Propane

C C

H

CH3

H

H

H

H

OR?

CH3

HH

H

HH

CH3

H H

H

H

H

C C

H

CH3

H

H

H

H


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From Bro n

70% anti an 0% auche


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cyclohexane

is NOT flat!

HH

H

H

H

H

H

H

H

H

H

H

chair conformation


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HH

H

H

H

H

H

H

H

H

H

H

H

HH

H

H

HH

H

all staggered

HH

H

H

H

H

H

H

H

H

H

H


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there are two types ofH's

H

H

H

H

H

H

H

HH

H

HH

H H

H

H

H

H

H

H

H

H

H

H

axial equatorial


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HH

H

H

H

H

H

H

H

H

H

H

HH

H

H

H

H

H

H

H

H

H

H

rapi

00,000 times persecon at room temperature


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Mono-substituted cyclohexanes

CH3

CH3

axial equatorial

9

.3 J. ol

-1

lessstable


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Response to student question


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Stereochemistry

Isomers(Same molecular formula)


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Stereochemistry


Constitutional isomers Stereoisomers


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Stereochemistry



(Different atom connectivity) (Same atom connectivity

Different arran ement in space)

H3C CH3CH3

CH3

oth C8H16


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Stereochemistry



(Different atom connectivity) (Same atom connectivity

Different arran ement in space)

DiastereoisomersEnantiomers


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Stereochemistry

Enantiomers(Non-superimposable mirror ima es)

Br

Cl H

F

Br

ClH

F

Stereo enic centre

Dissymmetric or chiral

Simplest case:

one asymmetric carbon


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Stereochemistry

Chiral objects


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Stereochemistry

Mirror ima es


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Stereochemistry

Molecules ith internal mirror planes are achiral

(superimposible mirror ima es)

Br

Cl H

H

Br

ClH

H


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StereochemistryMolecules ith internal mirror planes are achiral

Br

Cl H

H

Br

ClH

H

HH

Br

Cl


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Stereochemistry

Most chiral molecules in nature exist as a sin le enantiomer

CHO

OHH

HHO

OHH

OHH

CH OH

lucose

H NOH

O

H

leucine

OH

menthol

N

N

nicotine

H


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Stereochemistry

Namin enantiomers

Br

ClH

Br

ClH

1

2

3

4 4

3

2

1

S- R-

Pens Down


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Stereochemistry

Diastereoisomers are stereoisomers that are not enantiomers

H

H C

CH

H

H

H C

H

CH

E-but- -ene

Z-but- -ene

cis-

trans-

CHO

HHO

OHCH OH

H

CHO

OHH

OH

CH OH

H

threose

erythrose


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Diastereoisomers in cyclic molecules

imet ylcyclo utanes

dias r is m rs

c ns itutionalisom rs

cis trans

1,1-dim thyl 1,3-dim thyl


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Diastereoisomers in cyclic molecules

, imet ylcyclobutanes

ci s tr s

diastereoisomers ena ntiomers


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Stereochemistry

For n stereocentres there is a maximum of n stereoisomers

CH

HH

H

CH2 H

H

CH

HH

H

CH2 H

H

CH

HH

H

CH2 H

H

CH

HH

H

CH2 H

H

enantiomers

enantiomers

iastereoisomers


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Stereochemistry

Meso compounds have stereocentres but are achiral

CH2 H

HH

H

CH2 H

H

CH2 H

HH

H

CH2 H

H

CH2 H

HH

H

CH2 H

H

CH2 H

HH

H

CH2 H

H

meso

enantiomers

identical


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Delocalisation and Resonance

be ze e

reso a ce stablisatio


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O

R OH

carboxylic acid

- H+O

R O

O

R O

O

R O

O

R O

O

R O

carboxylate anion


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O

NR O

O

NR O

O

NR O

nitro roup

O

NR O

-2

-2


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O

R R

O

R R

ketones

O

R NH2

O

R NH2

amides


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Acidity and Basicity

HCl 4 RS 3H RC 2H R H

-10 0 5 16

aci

pKa

co jugate base

O

ClO

O

O

O

S

R O

O

O

R OR O


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ROH

16

OH

10pKa

O O O O


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R C

H

HHC

O

RH

HH

C

O

RC

R

O

H H

ca 50 ca 20 ca

R C

H

HR

CCH2

O

C

O

R CH2

C

O

RC

R

O

H

C

O

RC

R

O

H

C

O

RC

R

O

H

Carbon acids

enolate


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NH3OH H-

OH NH+

pKaHca 9

R NH2

ca 11

NH2

ca

C

O

R NH2

ca

RC

NH2

O

NH2

Documents

Peter Steel s ENCH241 Part1-1