1. Homologous series

2. Homologous series
A homologous series is a series of organic compounds of the same family which differ by a common structural unit.
Functional group: hydroxyl (OH) – each member differs by CH2

3. Homologous series
Members of a homologous series have similar chemical properties.
They also show a gradation in physical properties (such as the increasing boiling point of the alkanes).

4. Homologous series Members of a homologous series: differ by a CH2
have the same general formula
have similar chemical properties
show a gradation (gradual increase) in physical properties such as boiling point

5. Functional groups

6. Functional groups
A functional group is a group of atoms within a molecule that are responsible for the characteristic chemical reactions of the molecule.
Class: alcohols
Functional group: OH (hydroxyl) group
pentan-1-ol
Compounds that have the same functional group can be divided into classes.

11. Naming alkanes, alkenes and alkynes

12. Naming organic compounds

13. Alkanes (C-C) General formula CnH2n+2
CH4 methane
CH3CH3 ethane
CH3CH2CH2CH3 butane
CH3(CH2)4CH3 hexane
General formula CnH2n+2
Saturated hydrocarbons (C-C single bonds)

14. Alkenes (C=C) CH2CH2 ethene CH2CHCH3 propene CH3CHCHCH2CH3 pent-2-ene
General formula CnH2n
Unsaturated hydrocarbons (C=C double bond)

15. Alkenes (C=C)
C6H12 hex-2-ene
C6H12 hex-3-ene

16. Alkynes (C C) CHCCH3 CHCH CH3CCCH3 propyne ethyne but-2-yne
General formula CnH2n-2

17. Alkynes (C C)
hex-1-yne
CHC(CH2)3CH3
hex-2-yne
CH3CC(CH2)CH3

18. Esters

19. Esters ⇌ ⇌ Alcohols and carboxylic acids react to form esters
H2SO4
ester link ⇌ ⇌
This is a nucleophilic substitution reaction.
It is also called a condensation or esterification reaction.

20. Naming esters ⇌ alcohol is ethanol → ethyl
H2SO4
alcohol is ethanol → ethyl
carboxylic acid is ethanoic acid → ethanoate
ethyl ethanoate

21. Naming esters
ethanoate
ethyl
ethyl ethanoate

22. Naming esters
methanoate
propyl
propyl methanoate

23. Naming esters ⇌ alcohol is propan-1-ol → propyl
H2SO4 ⇌
alcohol is propan-1-ol → propyl
carboxylic acid is methanoic acid → methanoate
propyl methanoate

24. Esters Esters have distinctive fruity smells.
Esters are used as natural and artificial food flavorings.
They are also used as solvents in perfumes and as plasticizers.

25. Classification of organic compounds

26. Classification of alcohols
primary carbon atom
secondary carbon atom
propan-1-ol
primary alcohol
propan-2-ol
secondary alcohol
tertiary carbon atom
2-methylpropan-2-ol
tertiary alcohol

27. Classification of halogenoalkanes
1-chloropropane
primary halogenoalkane
2-chloropropane
secondary halogenoalkane
2-chloro-2-methylpropane
tertiary halogenoalkane

28. Classification of amines
propanamine
primary amine (primary N atom)
N-methylpropanamine
secondary amine
(secondary N atom)
N,N-dimethylpropanamine
tertiary amine (tertiary N atom)

29. Structural formulas

30. Structural formulas full structural formula butane molecular formula
empirical formula
condensed structural formula
skeletal formula

31. Structural formula but-1-ene full structural formula molecular formula
empirical formula
condensed structural formula
skeletal formula

32. Skeletal formulas 2,3-dimethylpentane butanal hex-2-yne butanone
propan-1-ol
ethyl butanoate

33. Stereochemical formula
The two solid lines are in the plane of the paper
The wedge is coming out from the paper
The dotted line is going into the paper

34. Structural isomers

35. 2-methylbutane (CH3)2CHCH2CH3 2,2-dimethylpropane C(CH3)4
Structural isomers
Structural isomers are compounds with the same molecular formula but different arrangements of atoms.
Structural isomers of C5H12
pentane CH3(CH2)3CH3
2-methylbutane (CH3)2CHCH2CH3
2,2-dimethylpropane C(CH3)4

36. Structural isomers Draw and name the structural isomers of C6H14
hexane CH3(CH2)4CH3
2,2-dimethylbutane (CH3)3CCH2CH3
2,3-dimethylbutane (CH3)2CHCH(CH3)2
2-methylpentane (CH3)2CHCH2CH2CH3
3-methylpentane CH3CH2CH(CH3)CH2CH3

37. hex-2-ene CH3CHCH(CH2)2CH3 hex-3-ene CH3CH2CHCHCH2CH3
Structural isomers
Structural isomers of the alkenes - C6H12
hex-1-ene CHCH(CH2)3CH3
hex-2-ene CH3CHCH(CH2)2CH3
hex-3-ene CH3CH2CHCHCH2CH3

38. Boiling points of organic compounds

39. Boiling points of the alkanes
As the molar mass of the compound increases, the boiling point increases.

40. Boiling points of the alkanes
As the molar mass increases, the strength of the London dispersion forces between the molecules increases.
More energy is required to overcome the London dispersion forces between the molecules, therefore the boiling point increases.

41. Branched vs straight chain
Branched isomers have lower boiling points than straight chain isomers.
The branches prevent the molecules getting close together which reduces the strength of the London dispersion forces and lowers the boiling point.

42. Effect of functional group
Functional group containing H bonded to O or N – hydrogen bonding between molecules
Functional group containing carbonyl group – dipole-dipole forces between molecules

43. Effect of functional group
Alcohols, amides and carboxylic acids have higher boiling points – they are able to form hydrogen bonds between molecules.

44. Effect of functional group
Aldehydes, ketones, and esters have dipole-dipole forces between molecules.

45. Effect of functional group
Alkanes, alkenes and alkynes have London dispersion forces between molecules.

46. Effect of functional group
low volatility
amides (hydrogen bonding)
carboxylic acids (hydrogen bonding)
alcohols (hydrogen bonding)
Increasing boiling
point
ketones (dipole-dipole forces)
aldehydes (dipole-dipole forces)
esters (dipole-dipole forces)
high volatility
alkanes (London dispersion forces)

47. Summary Factors that affect the boiling points of organic compounds:
Molar mass
Branched / straight chains
Functional group / intermolecular forces between molecules

48. Naming aldehydes and ketones

49. Naming aldehydes and ketones
HCHO
methanal
CH3CHO
ethanal
CH3CH2CHO
propanal

50. Naming aldehydes and ketones
CH3COCH3
propanone
CH3COCH2CH3 butanone

51. Naming aldehydes and ketones CH3COCH2CH2CH3 pentan-2-one

52. Naming organic compounds

53. Naming alcohols and carboxylic acids

54. Naming organic compounds

55. Naming alcohols CH3OH methanol CH3CH2OH ethanol CH3CH2CH2OH
propan-1-ol
General formula CnH2n-1OH

56. Naming carboxylic acids
HCOOH
methanoic acid
CH3COOH
ethanoic acid
CH3CH2COOH
propanoic acid
General formula CnH2n+1COOH

57. Reactions of the alkanes

58. Reactions of the alkanes
Alkanes have low reactivity
the C-H bond is a non-polar bond
the C-C and C-H bonds are strong
(C-C 348 kJmol-1 C-H 412 kJmol-1)

59. Reactions of the alkanes
Alkanes undergo combustion reactions
Complete combustion
polymerization
Incomplete combustion

60. Reactions of the alkanes
Alkanes undergo substitution reactions
Initiation – occurs in the presence of UV light
polymerization
Photochemical homolytic fission – the bond between the chlorine atoms is split by UV light with each chlorine atom taking one electron.

61. Reactions of the alkanes
Propagation
polymerization

62. Reactions of the alkanes
Termination
polymerization

63. Reactions of the alkanes
polymerization

64. Addition reactions of the alkenes

65. Addition reactions of the alkenes
Alkenes undergo addition reactions σ π
Alkenes are reactive as the π bond is easily broken to form two new bonding positions.

66. Addition reactions of alkenes
Hydrogenation – alkenes react with hydrogen in the presence of a nickel catalyst at a temperature of 150oC to form alkanes
Ni 150oC
Ni 150oC

67. Addition reactions of alkenes
Alkenes react with halogens to produce dihalogeno compounds (brown to colourless).

68. Addition reactions of alkenes
Alkenes react with hydrogen halides (HCl, HBr and HI) to produce halogenoalkanes.

69. Addition reactions of alkenes
Hydration - alkenes react with steam in the presence of a sulfuric acid catalyst to form alcohols.
H2SO4
H2SO4
H2SO4

70. Addition polymerization
ethene monomers
polymer polyethene
repeating unit

71. Reactions of the alcohols

72. Reactions of the alcohols
Alcohols undergo combustion in excess oxygen (complete combustion) to form carbon dioxide and water.
polymerization

73. Reactions of the alcohols
Primary alcohols are oxidized by acidified potassium dichromate(VI) (Cr2O72-/H+) and heat to form aldehydes or carboxylic acids.
Cr2O72-/H+
heat distillation
heat reflux
Colour change orange to green (Cr2O72- ion is reduced to the Cr3+ ion)

74. Reactions of the alcohols
Secondary alcohols are oxidized by acidified potassium dichromate(VI) (Cr2O72-/H+) and heat to form ketones
Cr2O72-/H+
heat reflux
Colour change orange to green (Cr2O72- ion is reduced to the Cr3+ ion)

75. Reactions of the alcohols
Tertiary alcohols cannot be oxidized by acidified potassium dichromate(VI) (Cr2O72-/H+) (no H atoms bonded directly to C-OH)
Cr2O72-/H+
no reaction
No colour change (orange)

76. Halogenoalkanes

77. Halogenoalkanes General formula CnH2n+1X
Halogenoalkanes contain an atom of fluorine, chlorine, bromine or iodine.
Iodoethane
1-chloropropane
2-bromobutane

78. Halogenoalkanes
Halogenoalkanes undergo substitution nucleophilic reactions (the replacement of one atom by another atom or group).
The halogen is more electronegative than the carbon atom forming a polar bond.
The halogen has a partial negative charge and the carbon has a partial positive charge (electron deficient).

79. Nucleophiles
Nucleophiles are electron rich species that contain a lone pair of electrons that it donates to an electron deficient carbon.
The hydroxide ion (nucleophile) is attracted to the electron deficient carbon in the halogenoalkane.

80. Halogenoalkanes chloromethane methanol+
chloromethane methanol
The conditions are warm with aqueous NaOH.

81. Halogenoalkanes propan-1-ol 1-bromopropane
Halogenoalkanes react with alkalis such as NaOH to form alcohols.
The hydroxide ion behaves as a nucleophile.

82. Structure of benzene

83. Structure of benzene Benzene is an aromatic unsaturated hydrocarbon
Molecular formula C6H6
Empirical formula CH
In 1865 Friedrich August Kekulé suggested that benzene contained a ring of six carbon atoms with alternating single and double bonds.

84. Structure of benzene
The Kekulé structure of benzene consists of alternating single and double bonds.
The actual structure of benzene is a resonance hybrid structure with delocalized electrons.

85. Structure of benzene
The C to C bonds are of identical length and strength
The length and strength of the C to C bonds in benzene are intermediate between a single and a double bond.

86. Structure of benzene ΔH = -120 kJmol-1 ΔH = -360 kJmol-1
The enthalpy of hydrogenation of benzene is less than predicted
ΔH = -120 kJmol-1
ΔH = -360 kJmol-1
ΔH = -210 kJmol-1
Delocalization of electrons minimizes the repulsion between the electrons, lowering the internal energy by 150 kJmol-1 (resonance energy)

87. Structure of benzene
Benzene undergoes substitution reactions, rather than addition reactions.
Only one isomer exists for compounds such as 1,2-dibromobenzene

88. Structure of benzene Benzene has delocalized π electrons
π bonded region
The π electrons form a delocalized π electron cloud above and below the plane of the ring.

89. Reactions of benzene

90. Reactions of benzene
π bonded region
The delocalized electrons give benzene extra stability, therefore it does not undergo addition reactions.
Benzene undergoes electrophilic substitution reactions in which a hydrogen atom is replaced by an incoming group.

91. Reactions of benzene
An electrophile is a reactant which is electron deficient (has a partial positive charge).
The electrophile is attracted to the electron rich benzene ring.

92. Reactions of benzene
Reaction with chlorine (Cl2)

93. Reactions of benzene
Reaction with nitric acid (HNO3)