1. ORGANIC CHEMISTRY
AS Module 3

2. NAMING 1
Look for the longest carbon chain. This gives the base name for your molecule:
1 C = methan- 2 C = ethan-
3 C = propan- 4 C = butan-
5 C = pentan- 6 C = hexan-

3. E.g. Name me:
3-methylhexane

4. FUNCTIONAL GROUPS
Functional group = an atom or group in the molecule that determines the chemical properties
Recognise the reactive group in the molecule.
When you know the functional group you can predict the reactions of the molecule
E.g. CH3CH2-OH
CH3CH2-Br
CH3-CHO
CH3-COOH
CH2=CH2
CH3-CN

5. -CHO and –CH2OH Aldehydes have the -CHO grouping. E.g. propanal:
Alcohols have the -CH2OH grouping E.g. propan-2-ol

6. NAMING 2
Identify the functional groups/substituents and number the carbons in the chain, starting from one end, to keep the number of the functional group or substituent as low as possible.
Remember that a functional group gets priority for low numbering.

7. E.g. Name me:
5-chloropentan-2-ol

8. NAMING 3 Substituents are named in front of the base name.
Remember di- = 2, tri- = 3 etc. if there is more than one of the particular substituent attached.
And remember to specify positions on the chain.

9. E.g. Name me:
3,4,4-trichloropentanal

10. ISOMERISM STRUCTURAL & STEREO
STRUCTURAL = Same molecular formula, atoms(groups) bonded in different places:
Chain
Position
Functional group
STEREO = Same molecular formula and structure, atoms(groups) arranged differently in space:
Geometrical (cis/trans)
Optical (next year)

11. CHAIN ISOMERISM Structural isomers with different carbon chains:
E.g. for C5H12:

12. POSITION ISOMERISM
Structural isomers with different positions for the functional group:
E.g. for C3H7OH:

13. FUNCTIONAL GROUP ISOMERS
Structural isomers with different functional groups:
E.g. for C4H8O:

14. HOMOLOGOUS SERIES Same: Functional group Chemical reactions
General formula &
Gradually changing physical properties

15. ALKANES - SOURCE From? Crude Oil By?
1. Fractional Distillation Learn fractions, order of B.Pts. & uses
2. Cracking Be able to write an equation E.g. C14H30 can be cracked to give octane and ethene only
C14H30 ® C8H C2H4

16. 2 TYPES OF CRACKING THERMAL HIGH T + HIGH P ~800ºC FREE RADICAL
PRODUCES MORE ALKENE MOLECULES FOR PETROCHEMICALS
CATALYTIC
LOWER T + CAT.
~450ºC ZEOLITE
VIA CARBOCATION
TO GIVE MORE SMALL ALKANES FOR PETROL

17. ALKANES – PHYSICAL PROPERTIES
Symmetrical non-polar molecules
\ Intermolecular forces?
Weak Van der Waal’s
\ Low M.Pts. & B.Pts. compared to most covalent molecules of similar Mr
Also insoluble in water as they cannot form hydrogen bonds with water molecules

18. ALKANES - REACTIONS Saturated Hydrocarbons
Unreactive except for 2 major reactions:
Combustion: E.g. butane
C4H ?O CO H2O
Substitution by a halogen e.g. chlorine

19. FREE RADICAL SUBSTITUTION 1

20. FREE RADICAL SUBSTITUTION 2

21. HALOALKANES Polar molecules. Why?
So dipole-dipole forces and slightly higher M.Pts. etc. than the alkanes
Because of the bond polarity: d+C—Brd-
The carbon is attacked by nucleophiles (?)

22. Nucleophilic Substitution 1
Haloalkanes can be converted into:
Alcohols (NaOH(aq) + heat) CH3Br + OH- ® CH3OH + Br-
Amines (XS conc. NH3(aq) + heat) CH3Br + 2NH3 ® CH3NH2 + NH4+ + Br-
Nitriles (KCN(ethanol) + heat) CH3Br + CN- ® CH3CN + Br-

23. NUCLEOPHILIC SUBSTITUTION 2
Note the nucleophilic attack by the CN- ion. The lone pair on the C attacks

24. CURLY ARROWS They show movement of an electron pair
They start on a lone pair or on a covalent bond
Remember to show clearly the molecule or ion produced after each stage of the mechanism. Don’t forget charges on ions

25. LOOK AGAIN!
The examiner is very strict about curly arrows in mechanisms Note: an extra C is added to the chain.

26. Nitriles Useful Intermediates
Can be converted to carboxylic acids:
Reflux with dilute acid (or alkali)
E.g. CH3CN + 2H2O ® CH3COO- + NH4+
HYDROLYSIS
Can be converted to amines:
Heat in hydrogen with a Ni catalyst
E.g. CH3CN + 2H2 ® CH3CH2NH2
REDUCTION

27. NUCLEOPHILIC SUBSTITUTION 3
Ammonia as a nucleophile needs 2 stages:

28. ELIMINATION FROM A HALOALKANE
Refluxing a haloalkane with KOH dissolved in ethanol produces an alkene. E.g:
CH3CH2CH2Br + OH- ® CH3CH=CH2 + H2O + Br-
Note: The change of solvent leads to a different reaction The OH- acts as a base here (rather than as a nucleophile) as it picks up a proton.

29. Elimination Mechanism

30. ALCOHOLS Homologous series? Functional group –OH
Thus high M.Pts & B.Pts for typical covalent molecules, because?
Can form hydrogen bonds between molecules
Thus the smaller alcohols also mix with water.

31. 3 TYPES OF ALCOHOL Not Whiskey, Beer, and Wine! Primary 1º
Secondary 2º
Tertiary 3º
According to the no. of Carbons attached to the Carbon with –OH attached to it:

32. 1º 2º & 3º Alcohols
1º 2º 3º

33. Reactions of Alcohols 1 Oxidation
Oxidant of choice:
Acidified potassium dichromate
Colour change:
Orange to green when it oxidises something

34. Oxidation of 1º Alcohols
1º gives an aldehyde on heating and distilling off the product straight away:
CH3CH2OH + [O] ® CH3CHO + H2O
But refluxing the alcohol + oxidant gives the acid as the aldehyde is oxidised:
CH3CHO + [O] ® CH3COOH

35. Oxidation of 2º Alcohols
Here the oxidant will only produce the ketone:
CH3CH(OH)CH3 + [O] ® CH3COCH3 + H2O
Note that the extent of oxidation depends on how many C—H bonds can be broken during the oxidation. The carbon chain does not break unless the oxidation is very vigorous i.e. combustion?
CH3CH2OH + ?O2 ® 2CO2 + 3H2O

36. (Non) Oxidation of 3º Alcohols
Note that there are no C—H bonds on the carbon attached to the hydroxy group.
Therefore a tertiary alcohol will not be oxidised.

37. Identifying Alcohols
The fact that the alcohols respond differently to oxidation gives us a simple sequence of tests to identify the type:
1. Try oxidation of the alcohol If it does not oxidise it is tertiary
2. If it can be oxidised: Test the product of oxidation to see whether it is an aldehyde:

38. Tests for aldehydes
Both Tollens & Fehlings can be used. Quote one accurately:
Tollens: Warming an aldehyde with Tollens causes the colourless soln. to give a silver mirror
Fehlings: Warming an aldehyde with Fehlings causes the blue soln. to give a red/brown ppt.

39. Elimination from Alcohols
Heating an alcohol to 170ºC with conc. H2SO4 produces an alkene as a water molecule is eliminated.
The acid acts as a catalyst
CH3CH2CH(OH)CH3 ® H2O + mix of CH3CH2CH=CH2 and CH3CH=CHCH3 depending on which side of the C—OH the proton is removed from.

40. Elimination Mechanism

41. ALKENES Homologous series?
Non-polar Hydrocarbons \ type of intermolecular forces?
Van der Waals \ low M.Pts. Etc. compared to alcohols and immiscible with water.
Exhibit a form of stereoisomerism called Geometrical since there is no free rotation about the double bond:

42. Geometrical Isomerism
Cis but-2-ene
Trans but-2-ene

43. Reactions of Alkenes
The C=C double bond is very reactive since it is a centre of electron density. One of the bonds is weaker than the other and this breaks open on reaction leaving the basic carbon chain intact.
Thus alkenes undergo addition reactions and are attacked by electrophiles i.e?
ELECTROPHILIC ADDITION

44. Electrophilic Addition Reactions
Alkenes react with:
H—Br (or other hydrogen halides)
Br2 (a good test for alkenes as the brown colour of the bromine quickly fades to colourless)
Conc. H2SO4 (if the product is warmed with water an alcohol can be produced).

45. Electrophilic Addition Mechanism 1

46. Addition to Unsymmetrical Alkenes 1
When an unsymmetrical molecule like H-Br is added to an unsymmetrical alkene like propene, two products are possible but only one is produced in any quantity:
CH3CH=CH2 + H-Br ® CH3CH(Br)CH3 Very little of the 1-bromopropane is produced:

47. Addition to Unsymmetrical Alkenes 2
Reason?
The 2º carbocation produced on the way to bromopropane: CH3CHCH3 is more stable than the 1º carbocation produced on the way to 1-bromopropane: CH3CH2CH2+
Order of stability of carbocations: 3º > 2º > 1º

48. Addition to Unsymmetrical Alkenes 3
Remember to draw the carbocations when discussing stabilities
In order to write correct equations, if you are not asked for the mechanism, just remember that: The d+ part of the electrophile attaches to the carbon of the double bond which has most hydrogens (NOT an explanation!)

49. Electrophilic Addition Mechanism 2

50. Hydrogenation of Alkenes
Alkene + Hydrogen + Heat with Ni catalyst
Used to convert Unsaturated(?) vegetable oils into more saturated margarine.
The fewer the double bonds the harder the margarine.
E.g: R—CH=CH2 + H2 ® R—CH2-CH3

51. Polymerisation of Alkenes
Also an addition reaction:
Mechanism = free radical
n CH2=CH2 ® --(-CH2—CH2-)n-
Polyethene
n CH2=CHCl ® --(-CH2—CHCl-)n-
Polychloroethene or PVC
Polystyrene from styrene CH2=CHC6H5 ?

52. Epoxyethane 1 A very useful compound made from ethene
Ag catalyst. Heat. In oxygen or air

53. Epoxyethane is very reactive because of the very strained 3 membered ring structure.
The bonds in the ring are forced to be at 60º to each other rather than the usual 109½º for tetrahedral and hence one of the C—C bonds breaks open easily (rather like an alkene)
Thus epoxyethane reacts easily with water and with alcohols: (Warming with dilute acid catalyst).
With excess water ethane-1,2-diol is formed – used as antifreeze and as a raw material for making polyesters.
With less water several epoxyethane molecules can add on to form polymeric polyethene glycols – uses?
Similarly for the alcohol reactions
MAKE SURE YOU CAN WRITE THE EQUATIONS

54. EPOXYETHANE + WATER

55. EPOXYETHANE + ALCOHOLS