1. +
AHL Organic Chemistry
Syllabus

2. +
20.1Prepare a student guide on naming
of the following 
 6 C atoms MAXIMUM :-
 Amine
 Amide
 Ester
 Nitrile
 Alcohol
 Aldehyde
 Ketone
 Carboxylic acid
 Halide
 MUST : Include functional group with 2 examples of each homologous series
 SHOULD : include branched examples
 COULD : include primary, secondary, tertiary

3. +
Nucleophilic Substitution Reactions
 Nucleophiles
 Why is hydroxide better than water ?

4. +
20.2.2 Identity of the halogen
 Consider the R-X bond
 RCl<RBr< RI

5. +
20.2.3 Nature of halogen effect on rate
 Review : Sn1 Sn2 reaction mechanisms, and rate data
 Rate : Tertiary > Secondary > Primary
 Sn1 route is faster as transition state ofSn2 has a higher
activation energy.

6. +
Study Questions
 Why don’t primary halogenoalkanes use the Sn1 mechanism.
 Why don’t tertairyhalogenoalkanes use Sn2 ?

7. +
Starter
 Explain how you would synthesise 2-methyl-amino-propane
from the appropriate haloalkane.

8. +
Draw structural formulae of …..
 1,2-dichlorobenzene
 Describe the bonding in this structure
 3-chlorohexanamide
 Describe the intermolecular forces present in this molecule
 The first 4 organic acids
 Describe and explain the boiling point trend.

9. +
Recap – what affects the relative
rate of Sn1 Sn2 reactions
 Nature of leaving group
 Primary >> Secondary >> Tertiary
 For Sn2 increasing nucleophile concentration increases rate –
no effect on Sn1.
 Increasing nucleophile strength favours Sn2 – hydroxide >>>
water

10. +
Completing the picture
 Substitution happens in competition with elimination reactions.
 Both reactions require REFLUX with NaOH ( or KOH )
 What decides elimination or substitution ?
 Primary – mainly substitution
 Tertiary – mainly elimination
 Water solvent favours substitution
 Ethanol solvent favours elimination
 Higher concentrations ( at elevated temperature ) of alkali favour
elimination

11. +
E2 mechanism ( E2 not on IB but..)
 Elimination from symmetrical haloalkanes.
 Elimination from unsymmetrical haloalkanes.

12. +
Stereoisomerism
 What ?
 compounds with the same structural formula but with different
arrangements of atoms in space.
 So give me some examples ……
 Consider 1,2-dibromoethane and 1,2-dibromoethene.

13. +
Cyclics also exhibit geometric
isomerism 
 Cyclopropane
 Cyclobutane

14. +
Physico-chemical properties of
geometric isomers
 Cis and trans 1,2-dichloroethene boiling points are 60C and
47C – why ?
 Cis and trans but-2-ene-1,4-dioic acid
 Cis forms the anydride BUT trans has no reaction……

15. Constitutional Isomers
 Have same molecular CH2 CH3
form but different
H3 C CH2
structural formula
butane
B.P = -0.5C
 Both isomers to the
right are C4H10 CH3
 These have different CH
chemical and physical H3C CH3
properties isobutane
B.P = -11.7 C

16. Stereoisomers
 Appear to have same structure in 2D
 In 3D have different structures
 Are non-superimposable mirror images of each other
 With modeling kit build a model: carbon atom with four different
colors attached (use same size bonds!)
 Look at your model in a mirror, build what you see in the mirror.
 Are the two superimposable?

17. Allmolecules have a mirror image –
but for most molecules it is the same
molecule.
H H
C C
H H
H H
F F
fluoromethane

18. +

19. For some molecules the mirror image
is a different molecule (the mirror
image is non-superimposable).
OH OH
C C
COOH HOOC
H H3C H
CH3
(-) lactic acid (+) lactic acid
in sour milk in muscles

20. • Left and right hands are an example
of non-superimposable mirror images.

21. Chirality Game  on blog please 

22.  Thisusually happens when a molecule contains a C atom
with four different groups attached (chiral / asymmetric C).
 Such molecules are said to be chiral or optically active.
a a
C C
d d
b c c b

23.  The optical isomers are called enantiomers.
 These are distinguished by +/-, D/L or more correctly R/S.
 A 50/50 mixture of the two enantiomers is called a racemic mixture or a racemate.

24. TASKWhich of the following molecules are optically
active?
1) propan-2-ol 5) butanone
2) 2-chlorobutane 6) 2-methylbutanoic acid
3) 1-chlorobutane 7) butan-2-ol
4) 3-methylhexane 8) 1-chloro-3-methylpentane

25. propan-2-ol
CH3 CH CH3
OH
NOT OPTICALLY ACTIVE

26. 2-chlorobutane
CH3 CH CH2 CH3
Cl
CH2CH3 CH2CH3
C C
CH3 H3C
H H
Cl Cl
OPTICALLY ACTIVE

27. 1-chlorobutane
CH2 CH2 CH2 CH3
Cl
NOT OPTICALLY ACTIVE

28. 3-methylhexane
CH3 CH2 CH CH2 CH2 CH3
CH3
CH2CH2CH3 CH2CH2CH3
C C
CH3 CH3
H H
CH2CH3 CH3CH2
OPTICALLY ACTIVE

29. butanone O
CH3 C CH2 CH3
NOT OPTICALLY ACTIVE

30. 2-methylbutanoic acid CH3 O
CH3 CH2 CH C OH
CH2CH3 CH2CH3
C C
H H
CH3 CH3
COOH HOOC
OPTICALLY ACTIVE

31. butan-2-ol OH
CH3 CH2 CH CH3
CH2CH3 CH2CH3
C C
H H
CH3 CH3
OH HO
OPTICALLY ACTIVE

32. 1-chloro-3-methylpentane CH3 Cl
CH3 CH2 CH CH2 CH2
CH2CH3 CH2CH3
C C
H H
CH3 CH3
CH2CH2Cl CH2ClCH2
OPTICALLY ACTIVE

33. How to draw 3D:
Dash-Wedge Formula
 Draw two straight lines H
about 110  from each
other
 Bond angle is 109.5 Cl OH
 These represent the bonds in
the plane of the page CH 3
 Draw dashed line for the
bond that extends behind
the plane of the page
 Draw wedge for bond that
extends in front of the
plane of the page

34. +
Drawing Enantiomers
 Draw the molecule you built, using the dash-wedge formula
and colored pens
 Use a mirror to see the enantiomer
 Sketch the mirror image, using the dash-wedge formula
 Draw the two stereoisomers of 1-chloro-1-bromo-ethane.
 There is no convention for which atom is attached to a wedge.

35. Chiral centers
 Carbon attached to 4 different substituent
groups
 Even if two substituent groups start with C, they could
still be different
H H
H3CH2C OH CH2CH3
HO
CH3 H3C
 C=O, never chiral (C only attached to 3 things)
 CH3,
CH2 groups, never chiral because they are
symmetric:

36. +
Vocabulary
 Stereoisomers have chiral centers.
 Carbon atoms can be
 chiral or achiral
 Asymmetric or symmetric
 If two molecules are stereoisomers, they are also called
enantiomers
 Chiral molecules are optically active
 Enantiomers are optical isomers

37. +
Properties of Optical Isomers
 same physical and chemical properties
 rotate plane polarized light
 Each isomer rotates it in a different direction
 What is plane polarized light?
 Try polarizers

38. +
Optical Activity
 Stereoisomers are said to be optically active if the rotate plane
polarized light
 Each type of enantiomer rotates light the same amount, but in
different directions.
 Amount and direction of rotation must be experimentally
determined using a polarimeter

39. Optical Activity
 The amount of rotation depends on
 Lengthof sample tube
 Concentration of enantiomers
 Bothisomers present, rotation cancels out
called: racemic mixture

40. Molecules that are optical isomers are
called enantiomers.
• Enantiomers have identical chemical
and physical properties, except:
• Their effect on plane polarised light;
• Their reaction with other chiral molecules

41. Light is a form of electromagnetic
radiation.

42. The wave vibrations are perpendicular
to the direction of travel of the wave.
normal light plane-polaris ed light plane-polaris ed light after
(w av es v ibrate in all direc tions ) (v ibrates in only one direc tion) c loc k w is e rotation

43. Optical isomers rotate the plane of
plane polarised light.
(-)-enantiomer (+)-enantiomer (±)-rac emate
(antic loc k w is e rotation) (c loc k w is e rotation) (no ov erall effec t)

44. +

45. • Chiral molecules often react differently
with other chiral molecules.
• This is like the idea that a right hand
does not fit a left handed glove – the
molecule must be the correct shape to
fit the molecule it is reacting with.
• Many natural molecules are chiral and
most natural reactions are affected by
optical isomerism.

46. • For example, most amino acids (and
so proteins) are chiral, along with
many other molecules.
• In nature, only one optical isomer
occurs (e.g. all natural amino acids are
rotate polarised light to the left).

47. Many drugs are optically active, with
one enantiomer only having the
beneficial effect.
In the case of some drugs, the other
enantiomer can even be harmful, e.g.
thalidomide.

48. In the 1960’s thalidomide was given to
pregnant women to reduce the effects
of morning sickness.
This led to many disabilities in babies
and early deaths in many cases.

49. +
O NH O O NH O
O O
H2C C C H2C
CH2 N N CH2
H H
O O
S thalidomide (effective drug) R thalidomide (dangerous drug)
The body racemises each
enantiomer, so even pure S is
dangerous as it converts to R in
the body.

50. Thalidomide was banned worldwide
when the effects were discovered.
However, it is starting to be used
again to treat leprosy and HIV.
Its use is restricted though and
patients have to have a pregnancy
test first (women!) and use two forms
of contraception (if sexually active).

51. CH3 CH3
O O
H C CH2 H2C C H
H3C CH3
S carvone (caraway seed) R carvone (spearmint)
Caraway Seed has a
warm, pungent, slightly bitter flavour with
aniseed overtones.

52. CH3 CH3
CH2 C H H C CH2
CH3 H3C
S limonene (lemons) R limonene (oranges)