1. 10.2 Functional group chemistry
Hydrocarbons

2. Essential idea
Structure, bonding and chemical reactions involving functional group inter-conversions are key strands in organic chemistry.

3. ALKANES General Formula: CnH2n+2 Alkanes are saturated hydrocarbons.
Hydrocarbons refer to compounds that contain hydrogen and carbon only.
Saturated means they contain all single carbon-carbon bonds.

4. LO-1 Alkanes have low reactivity and undergo free-radical substitution reactions.
Alkanes have low reactivity because alkanes have
Saturated nature
Non-polar character

5. ALKANES HAVE LOW CHEMICAL REACTIVITY
Alkanes contain only C-C and C-H bonds.
Both of these are strong bonds with bond enthalpies of 348 kJ/mol and 412 kJ/mol, respectively.
These molecules will only react in the presence of a source of energy strong enough to break these bonds.
Most alkanes are stable under most conditions and can be stored, transported and compressed safely.
The C-C and C-H bonds are non-polar so they are not susceptible to attack by most reactants.

6. Application and skills
Alkanes:
Writing equations for the complete and incomplete combustion of hydrocarbons.
Explanation of the reaction of methane and ethane with halogens in terms of a free-radical substitution mechanism involving photochemical homolytic fission.

7. Combustion Complete combustion Incomplete combustion
2CH4(g) + 3O2(g)             2CO(g)    +    4H2O(l)
Carbon monoxide is poisonous.

8. Why is Carbon Monoxide Poisonous?
Carbon monoxide acts as a poison by combining with hemoglobin in the blood. Hemoglobin normally reacts with oxygen from the air and transports the oxygen to the parts of the body which need it. Carbon monoxide is much more reactive with hemoglobin than oxygen is. It combines to form a stable compound with hemoglobin, preventing the transport of oxygen around the body. The person dies by suffocating from the inside (nasty!).

9. Halogenations
Reaction of methane with chlorine Reaction of ethane with chlorine

10. Homolytic Fission and Free radical substitution

11. Learning outcomes Understand
Alkenes are more reactive than alkanes and undergo addition reactions.
Application and Skills
Write equations for the reactions of alkenes with hydrogen and halogens.
Write equations for the reactions of symmetrical alkenes with hydrogen halides and water.
Outline the addition polymerization of alkenes.

12. Reactions of Alkenes
Hydrocarbons that have –C=C- undergo addition reactions.
Addition of hydrogen ( alkene to Alkane)
Reaction conditions
Catalyst : Nickel( Pt or Pd)
Temperature : 573 K or 300 oC 12

14. Reactions of Alkenes
Addition of halogen to alkene

15. Reaction of Alkenes
Reaction of Alkenes and Hydrogen halides

16. Reaction of Alkenes
Reaction of ethene and water gives ethanol

17. Test to differentiate between Alkane and Alkene
Alkenes decolorize bromine water
Animation
Video

18. POLYMERIZATION
Alkenes readily undergo addition reactions by breaking their double bond.
They can be joined together to produce long chains known as polymers.
The alkene used in the reaction is known as the monomer and its chemical nature will determine the properties of the polymer.
H H H H
C=C has the repeating unit -C-C-
H H H H n

19. Polymerization

20. ECONOMIC IMPACT
Alkenes are used as starting materials in the manufacture of many industrially important chemicals.
Polymers are a major product of the organic chemical industry.
Most of our most common and useful plastics are polymers of alkenes.

21. Ethene polymerizes to form polyethene also known as polythene
Ethene polymerizes to form polyethene also known as polythene. (structure shown previously)
It has excellent insulating properties.
It played an essential role in the development of radar during World War II.
It is commonly used in household containers, carrier bags, water tanks and piping.

22. Propene polymerizes to form polypropene often called polypropylene.
It is used in the manufacture of clothing.
More specifically the production of thermal wear.
H H H H
C=C has the repeating unit -C-C
H CH H CH3 n

23. Polychloroethene is known as PVC, poly vinyl chloride.
It is one of the world’s most important plastics.
It is used in construction materials, packaging, and electrical cable sheathing.
Its synthesis produces dioxins which are toxic and are linked to a variety of cancers.
H H H H
C=C has the repeating unit -C-C -
H Cl H Cl n

24. Polytetrafluoroethene is known as PTFE It is often marketed as Teflon.
F F F F
C=C has the repeating unit -C-C -
F F F F n

25. Alkene Reaction Summary

26. 10.2 Functional group chemistry
Alcohols

27. Learning outcomes Understand:
Alcohols undergo esterification (or condensation) reactions with acids and some undergo oxidation reactions
Apply their knowledge to:
Write equations for the complete combustion of alcohols.
Write equations for the oxidation reactions of primary and secondary alcohol (using either acidified potassium dichromate(VI) or potassium manganate(VII) as the oxidizing agent).

28. Learning outcomes Apply knowledge to:
Explain the importance of distillation and reflux in the isolation of the aldehyde and carboxylic acid products when primary alcohols are oxidized.
Write the equation for the condensation reaction of an alcohol with a carboxylic acid, in the presence of a catalyst (e.g. concentrated sulfuric acid) to form an ester.

29. ALCOHOLS General Formula: CnH2n+1OH
Alcohols contain the –OH functional group.
The –OH group is polar and increases the solubility in water and the volatility of alcohols when compared to alkanes of similar molar mass.

30. COMBUSTION OF ALCOHOLS
Alcohols react with oxygen to produce CO2 and H2O.
These reactions produce significant amounts of energy.
The amount of energy released increases as we go up a homologous series because more CO2 is produced.
As in the case with hydrocarbons, in the case of limited oxygen, CO will be produced instead of CO2.
2CH3OH + 3O2 → 2CO H2O

31. Esterification
An alcohol reacts with an alkanoic acid to form an ester and water. 15

32. Oxidation
Alcohols are oxidized to alkanals (aldehydes) or alkanones (ketones 9

33. Primary Alcohols are Oxidized to Alkanals
The most common oxidizing agents are KMnO4 in basic solution, K2Cr2O7 in acidic solution, or oxygen from the air. The mechanisms of such reactions are usually complex
Animation
Aldehyde
Animation
Carboxylic acid 10

35. Secondary Alcohols are oxidized to Alkanones11

37. Tertiary Alcohols are not easily oxidized12

38. Evidence for oxidation of alcohols
Video

39. Halogenoalkanes

40. Learning outcomes Understand:
Halogenoalkanes are more reactive than alkanes.
Halogenoalkanes can undergo nucleophilic substitution reactions.
Nucleophiles are electron-rich species containing a non-bonding pair of electrons that is donated to an electron-deficient carbon
Apply their knowledge to:
Write equations for the substitution reactions of halogenoalkanes with aqueous sodium hydroxide.

41. HALOGENOALKANES General Formula: CnH2n+1X (X=Halogen)
Halogenoalkanes contain an atom of fluorine, chlorine, bromine or iodine bonded to the carbon skeleton of the molecule.
Due to the presence of the halogen, they possess a polar bond unlike the non-polar alkanes.

42. Boiling points of some isomers
Draw a conclusion about relationship between branching and boiling points of halogenoalkanes

43. Reactivity of halogenoalkane

44. Reactivity of halogenoalkanes
Bond strength Vs Bond Polarity
Bond strength is the winner

45. Nucleophiles
A nucleophile is a species (an ion or a molecule) which is strongly attracted to a region of positive charge in something else.
Nucleophiles are either fully negative ions, or else have a strongly - charge somewhere on a molecule. Common nucleophiles are hydroxide ions, cyanide ions, water and ammonia.

46. The nucleophiles are attracted to the electron deficient carbon in the halogenoalkane which leads to a reaction where substitution of the halogen occurs.
This reaction is called Substitution Nucleophilic and has the shorthand notation of SN.
During this reaction, the carbon-halogen bond breaks and the halogen is released as a halide ion.
When both of the shared electrons go to one product, it is known as heterolytic fission.
The halogen that becomes detached is sometimes referred to as the leaving group.
C2H5Br + OH- → C2H5OH + Br-

47. Nucleophilic substitution reactions.
Halogenoalkanes undergo nucleophilic substitution reaction
Simples way to write

48. OH1- as Nucleophile
The halogenoalkane is usually refluxed with aqueous sodium hydroxide, NaOH(aq), but some RX molecules are reactive enough to hydrolyse when just mixed with water

49. Benzene

50. Learning outcomes Understanding
Benzene does not readily undergo addition reactions but does undergo electrophilic substitution reactions.

51. Reactivity of benzene
Benzene does not readily undergo addition reaction due to delocalized bonding
Benzene undergo electrophilic substitution reaction

52. Benzene and electrophiles
Because of the delocalised electrons exposed above and below the plane of the rest of the molecule, benzene is obviously going to be highly attractive to electrophiles - species which seek after electron rich areas in other molecules
The electrophile will either be a positive ion, or the slightly positive end of a polar molecule.
Benzene undergo substitution reaction because it needs high energy to break delocalized electron cloud.

53. Examples of substitution reactions
Nitration
Chlorination