1. Introduction To Organic Chemistry

2. Lecture 1 12.1 Introduction Learning Outcomes:
At the end of the lesson the students should be able to :
List the elements that made up organic compounds C, H, O, N, P, S and halogens.
State the ability of carbon to form 4 covalent bonds with other carbons or elements.
Differentiate between saturated and unsaturated organic compounds.
Give examples of organic compounds used in medicine, engineering, biotechnology and agriculture.

3. WHAT IS ORGANIC CHEMISTRY?
Organic chemistry is the chemistry of carbon compounds.
Organic compounds contain H as well as C, while other common elements are O, N, the halogens, S and P.
There are many varieties of organic compounds
( more than 10 millions!!!)
They may exist as simple or complex molecules; as gases, liquids or solid and coloured or colourless.

4. Examples :-
CH4
methane (a component of natural gas)
methyl salicylic acid (aspirin-a drug)

5. penicillin (an antibiotic)
dichlorodiphenyltrichloroetane
(DDT- a pesticide component)

6. All organic compounds consist of carbon atom.
Properties of carbon atom:
-has 4 valence electrons.
-can form 4 covalent bonds.
C C
C C
C C
Single bond
Double bond
Triple bond

7. Hydrocarbons saturated unsaturated
Contains only single bonds ( -C-C- )
Examples: alkanes,
cycloalkanes
Contains at least one carbon-carbon double bond (-C=C-) or triple bond (-C C-).
Examples: alkenes, alkynes.

8. Uses of organic compounds
Medicine
Antibiotics are used to fight bacterial and fungal infections
Engineering
Gasoline-as a fuel for internal combustion engines.
Biotechnology
Genetic information like DNA
Agriculture
DDT-as insectisides to kill harmful insects.

9. Lecture 2: 12.2 Molecular and Structural Formulae
Learning Outcomes:
At the end of the lesson the students should
be able to :
Define structural formula.
Draw structural formula in the form of expanded, condensed and skeletal structures based on the molecular formula.
Explain primary (1°), secondary (2°), tertiary (3°) and quaternary (4°) carbon.

10. 3 types of structural formula:
Structural formula shows how the atoms in a molecule are bonded to each other.
3 types of structural formula:
condensed structure
expanded structure
skeletal structure

11. 2- Dimensional formula
Condensed Structure
Does not show single bonds between carbon and hydrogen atoms, but double and triple bonds are shown.
All atoms that are attached to a carbon are written immediately after that carbon.
C4H9Cl CH3CHCH2CH3
(Condensed structure)

12. Examples:
ii) Cyclohexane, C6H12
iii) Aldehyde, CH3CHO O
CH3CH

13. Expanded Structure
Expanded structures indicate how atoms are attached to each other but are not representations of the actual shapes of the molecules.
C4H9Cl
Molecular
Formula
Expanded structure
C C C C H Cl

14. Examples:
i) Alcohol (C2H6O)
ii) Carboxylic acid (C3H6O2 )

15. Shows only the carbon skeleton. Hydrogen atoms are not written.
Skeletal Structure
Shows only the carbon skeleton.
Hydrogen atoms are not written.
Other atoms such as O, Cl, N etc. are shown.
i) CH3CH(Cl)CH2CH = Cl
ii) =

16. 3- Dimensional formula ( wedge – dashed wedge – line formula )
Describes how the atoms of a molecule are arranged in space.

17. Example : Bromoethane or or Indication :- :bonds that lie in the plane
:bonds that lie behind the plane
:bonds that project out of the plane

18. Classification of C atoms:
A carbon atom can be classified as
primary carbon(1o) →bonded to 1 C
secondary carbon(2o) → bonded to 2 C
tertiary carbon(3o) → bonded to 3 C
quarternary carbon(4o) → bonded to 4 C

19. H
H C H
CH3
10 carbon
10 carbon

20. CH3
H C CH3
CH3
30 carbon

21. 1 H 1 H
CH3
CH3 1 1 H C C C
CH2 C
CH3 H H H
CH3 1

22. H H
CH3
CH3 2 H C C C
CH2 C
CH3 2 H H H
CH3

23. H H
CH3
CH3 3 4 H C C C
CH2 C
CH3 H H H
CH3

24. Question CH3(CH2)CCl(CH3)2 Expanded Structure Condensed Structure
Skeletal
Structure

25. 12.3 FUNCTIONAL GROUPS AND HOMOLOGOUS SERIES

26. Lecture 3 Functional Group and Homologous Series
Learning Outcomes:
At the end of the lesson the students should be able to :
Define functional group.
Name functional groups and classify organic compounds according to their functional groups.
Define homologous series and explain general characteristics of its members.

27. Functional group
is an atom or group of atoms in an organic molecule which characterised the molecule and enables it to react in specific ways which determines its chemical properties.

28. Functional groups are important for three reasons:
A basic by which organic compounds are divided into different classes.
A basic for naming organic compounds
A particular functional group will always undergo similar types of chemical reactions.

29. Homologous Series
is series of compounds where each member differs from the next member by a constant – CH2 unit
Members of the same homologous series are called homologs.

30. Homologs Features Obey a general formula:
Examples:
Alkane: CnH2n+2
Alkene: CnH2n
Alcohol : CnH2n+1OH
Differ from the successive homolog by a CH2 unit
Show a gradual change in the physical properties

31. Have same functional group
Have similar chemical properties
Can be prepared by similar general methods

32. Classification of organic compound
Class of Compound
Structure
Name
Example
Functional Group
Alkane
CH3-CH3
Alkene
-C=C-
carbon-carbon double bond
CH3CH=CH2
-C C-
Alkyne
carbon-carbon triple bond
CH3C CCH3

33. Aromatic
Benzene ring
-CH3
Haloalkane
X (F, Cl, Br, I)
Halogen
CH3Cl
Alcohol
-OH
Hydroxyl
CH3-OH
Phenol
Ether
-C-O-C-
Alkoxide
CH3-O-CH3

34. Aldehyde
-C=O H
Carbonyl
CH3-C=O
Ketone
R-C=O R
CH3
Carboxylic
acid OH
Carboxyl
Ester
-C-O-C- O
Carboalkoxy
OCH3
Acyl chloride Cl

35. Anhydride
O O
-C-O-C-
CH3C-O-CCH3
Amide
-C=O N-
Carboxamide
CH3-C=O
NH2
Amine
-NH2
Amino
CH3-NH2
Nitrile
-C N
Cyano group
CH3C N

36. Exercises:
1. Identify the functional group in the following
molecules
(CH3)3CCH2CH=CH2
(CH3)3CCH=CHCH2-OH

37. CH3 C CH
NH2 O
CH2 OH c)

38. 12.4 Isomerism Learning Outcomes:
At the end of the lesson the students should be able to :
Define isomerism.
Explain constitutional isomerism.
chain isomers
positional isomers
functional group isomer

39. Constitutional Isomerism
Structural/
Constitutional Isomerism
Stereoisomerism
diastreomer
enantiomer
Chain
Isomerism
Positional
Isomerism
Functional Group
Isomerism
cis-trans
isomerism
other
diastereomers

40. Isomerism
is the existence of different compounds with the same molecular formula but different structural formulae.
Different structural formula that have the same molecular formula are called isomers.

41. 1) Constitutional isomers (Structural isomers)
are isomers with the same molecular formula but differ in the order of attachment of atoms.
2) Stereoisomers
are isomers with the same molecular formula but different arrangement of atoms in space

42. Constitutional isomerism
Isomerism resulting from different order of attachment of atoms.
Three types
a) Chain/skeletal isomerism
b) Positional isomerism
c) Functional group isomerism

43. C5H12 CH3CH2CH2CH2CH3 CH3CHCH2CH3 CH3CCH3 CH3 CH3
a) Chain/skeletal isomerism
The isomers differ in the carbon skeleton
(different carbon chain).
They possess the same functional group and
belong to the same homologous series.
Example:
C5H12
CH3CH2CH2CH2CH3
CH3CCH3
CH3
CH3CHCH2CH3
CH3

44. CH3CH2CH2Cl CH3CHCH3 Cl 2)Positional isomerism
These isomers have a substituent group/ functional group in different positions.
Examples
C3H7Cl
CH3CH2CH2Cl
1-chloropropane
CH3CHCH3 Cl
2-chloropropane

45. C4H8 C8H10 C H CH2=CHCH2CH3 CH3CH=CHCH3 1-butene 2-butene
1,2-dimethylbenzene
1,3-dimethylbenzene
1,4-dimethylbenzene

46. C6H13N

47. 3)Functional group isomerism
These isomers have different functional groups and belong to different homologous series with the same general formula.
Different classes of compounds that exhibit functional group isomerism :-
General formula
Classes of compounds
CnH2n+2O ; n > 1
alcohol and ether
CnH2nO ; n ≥ 3
aldehyde and ketone
CnH2nO2 ; n ≥ 2
carboxylic acid and ester
CnH2n ; n ≥ 3
alkene and cycloalkane

48. Examples C2H6O C3H6O C3H6O2 CH3CH2OH CH3OCH3 ethanol dimethyl ether
propanone
propanal
propanoic acid
methyl ethanoate

49. Exercise:
State how many are isomers with the following molecular formulae, identify the type of isomerism and draw the structural formula of the isomers.
a) C5H10
b) C5H10O2
c) CH3CH=C(Cl)CH3
d) C4H6Cl2
e) CH3CH2CH(OH)CH(Br)CH2CH3

50. Lecture 5 12.4 Isomerism Learning Outcomes:
At the end of the lesson the students should be able to :
Define stereoisomerism.
Describe cis-trans isomerism due to restricted rotation about C=C bond and CC bond in cyclic compounds
Identify cis-trans isomerism of a given structural formula.

51. Stereoisomerism / optical isomerism :
Isomerism that resulting from different spatial arrangement of atoms
in molecules.
Two subdivisions of stereoisomers:
Enantiomers (mirror image)
Diastereomers (non-mirror image)

52. Diastereomer Cis-Trans Isomerism
 The requirements for geometric isomerism :
i) restricted rotation about a C=C,double bond in alkenes, or a C-C single bond in cyclic compounds.
ii) each carbon atom of a site of restricted rotation has two different groups attached to it.

53. Examples trans-2-butene cis-2-butene CH3 H H CH3
cis-1,2-dimethylcyclohexane
trans-1,2-dimethylcyclohexane

54. If one of the doubly bonded carbons has 2 identical groups, geometric isomerism is not possible.
Example
No cis – trans isomer

55. Lecture 6 12.4 Isomerism Learning Outcomes:
At the end of the lesson the students should be able to :
Identify cis-trans isomerism of a given structural formula.
Define chirality centre and enantiomers.
Identify chirality centre in a molecule.
Explain optical activity of a compound.
Draw a pair of enantiomers using 3-dimensional formula.
Define racemate.
State the applications of chiral compounds in daily life.

56. Enantiomer Optical Isomerism
Optically active compounds have the ability to rotate plane-polarized light to the right (dextrorotary) and to the left (levorotary)
The angle of rotation can be measured with an instrument called polarimeter.

57. Polarimeter

58. The requirements for optical isomerism :-
molecule contains a chiral carbon or chirality centre or stereogenic centre (a sp3-hybridized carbon atom with 4 different groups attached to it)
ii) molecule is not superimposable with its mirror image.
PQRS
*designates chiral centre

59. a pair of mirror-image that are not superimposable. Example:-
Enantiomers
a pair of mirror-image that are not superimposable.
Example:-
i) 2-butanol ,
enantiomers

60. ii) 2-hydroxypropanoic acid,
enantiomers

61. Racemate
A racemic mixture or racemate is an equimolar mixture of enantiomers which is optically inactive because the two components rotate plane-polarized light equally (same degree of rotation) but in opposite directions.
Hence it does not give a net rotation of plane-polarized light.

62. Applications of chiral compounds in daily life.
e.g:
() Dopa is used for treatment of Parkinson’s disease but (+) dopa is toxic to human.
(S)-Ibuprofen the popular analgesic(the active ingredient in motrin, advil, and many other nonaspirin analgesics)

63. REACTIONS OF ORGANIC COMPOUNDS

64. Lecture 7 12.5 Reactions of Organic Compounds
Learning Outcomes:
At the end of the lesson the students should be able to :
Explain covalent bond cleavage:
homolytic
heterolytic

65. Types of Covalent Bond Cleavage/Fission
 All chemical reactions involved bond breaking and bond making.
 Two types of covalent bond cleavage :-
 Homolytic cleavage
 Heterolytic cleavage

66. a) Homolytic Cleavage
Occurs in a non-polar bond involving two atoms of similar electronegativity.
A single bond breaks symmetrically into two equal parts, leaving each atom with one unpaired electron.
Formed free radicals.

67. Example:
X : X
X X
free radicals X X  

68. b) Heterolytic cleavage
Occurs in a polar bond involving unequal sharing of electron pair between two atoms of different electronegativities.
A single bond breaks unsymmetrically.
Both the bonding electrons are transferred to the more electronegative atom.
Formed cation and anion.

69. A is more electronegative.
A: B+
anion cation
A : B
A is more electronegative.
A B:-
cation anion
B is more electronegative.

70. Reaction Intermediates
a) Carbocation
b) Carbanion
c) Free Radical
They are unstable and highly reactive.

71. a) Carbocation
Also called carbonium ion.
A very reactive species with a positive charge on a carbon atom.
Carbocation is formed in heterolytic cleavage.

72. Example :
 
(CH3)3C — Cl (CH3)3C Cl carbocation anion
Chlorine is more electronegative than carbon and the C—Cl bond is polar.
The C—Cl bond breaks heterolitically and both the bonding electrons are transferred to chlorine atom to form anion and carbocation.

73. b) Carbanion
is an anion counterpart
a species with a negative charge on a carbon atom.
Carbanion is formed in heterolytic cleavage.

74. example:
 
(CH3)3C — Li (CH3)3C Li carbanion kation

75. b) Free Radical A very reactive species with an unpaired electron.
Formed in homolytic cleavage.
Examples: i)
free radicals
Cl – Cl uv Cl● Cl ●

76. ii) C C ● C + ● C
iii) ● H ● + H
H3C
H3C

77. Lecture 7 12.5 Reactions of Organic Compounds
Learning Outcomes:
At the end of the lesson the students should be able to:
State the relative stabilities of primary, secondary and tertiary free radicals, carbocations and carbanions.
Explain the inductive effect of alkyl group towards the stability of carbocations and carbanions.
Define electrophile and nucleophile.

78. Relative Stabilities of Carbocations, Carbanions and Free Radicals
Carbocation, carbanion and free radical can be classified into:
Primary
Secondary
Tertiary

79. Carbocation Stability
The alkyl groups (electron-releasing group) stabilise the positive charge on the carbocation.
The stability of carbocation increases with the number of alkyl groups present.

80. Carbocation Stability:H C + H C R + R C H + R C +
<
<
<
Methyl
cation
Primary 10
Secondary 20
Tertiary 30
Increasing stability

81. Carbanion Stability
Alkyl group and other electron-donating groups destabilise carbanions.
Electron withdrawing group (e.g: halogen) stabilise carbanions through the inductive withdrawal of electron density

82. Carbanion Stability: H H R R H C H
< H C R
< H C R
< R C R - - - -
Methyl
anion
Primary 10
Secondary 20
Tertiary 30
Increasing stability

83. Free-radical stability
The stability of free radical increases as more alkyl groups are attached to the carbon atom with unpaired electron.

84. Free Radical Stability :H H R C .
Tertiary 30 H H C R H R C H C .
< .
< .
<
methyl
radical
Primary 10
Secondary 20
Increasing stability

85. Reagents and sites of organic reactions
A) Electrophile
Means ‘electron loving’.
An electron-deficient species and accepting electron from an attacking nucleophile.
Can be either neutral or positively charged

86. Examples of electrophiles :
cations such as H+, H3O+, NO2+ etc.
carbocations.
Lewis acids such as AlCl3, FeCl3, BF3 etc.
oxidizing agents such as Cl2, Br2 and etc.

87. -C = O (carbonyl) ; -C – X (haloalkanes) + -
electrophilic sites are molecules with low electron density around a polar bond
Examples:
+  + -
-C = O (carbonyl) ; -C – X (haloalkanes)
+ -
-C – OH (hydroxy compounds)
ii) i)
iii)

88. b) Nucleophile
means ‘nucleus loving’
An electron-rich species and electron-pair donor.
A nucleophile can be either neutral or negatively charged.

89. Examples of nucleophiles :
anions such as OH-, RO-, Cl-, CN- etc.
carbanions ( species with a negative charge on carbon atoms ).

90. Lecture 7 12.5 Reactions of Organic Compounds
Learning Outcomes:
At the end of the lesson the students should
be able to explain the main types of organic reactions:
addition: electrophilic and nucleophilic
substitution: electrophilic, nucleophilic and free radical
elimination
rearrangement

91. 4 Types of Organic Reactions
 Addition  Substitution  Elimination  Rearrangement

92. I) Addition Reaction
A reaction in which atoms or groups add to adjacent atoms of a multiple bond.
Two types of addition :-
a) Electrophilic Addition
b) Nucleophilic Addition

93. CH3CH=CH2 + Br2 CH3CHBrCH2Br electrophile
a)Electrophilic Addition
Initiated by an electrophile accepting electron from an attacking nucleophile.
Typical reaction of unsaturated compounds such as alkenes and alkynes.
Example :
CH3CH=CH2 + Br CH3CHBrCH2Br
electrophile
CCl4
Room
temperature

94. b) Nucleophilic Addition
Initiated by a nucleophile, which attacks an electrophilic site of a molecule.
Typical reaction of carbonyl compounds.  CN O +
HCN
CH3 C
CH3
CH3 C
CH3  OH

95. II) Substitution Reaction
A reaction in which an atom or group in a molecule is replaced by another atom or group.
Three types of substitution :-
a) free radical substitution.
b) electrophilic substitution.
c) nuclephilic substitution.

96. CH3CH3 + Cl2 uv light CH3CH2Cl + HCl
a) Free-radical Substitution
Substitution which involves free radicals as intermediate species.
Example :
CH3CH3 + Cl2 uv light CH3CH2Cl + HCl

97. b) Electrophilic Substitution
Typical reaction of aromatic compounds.
The aromatic nucleus has high electron density, thus it is nucleophilic and is prone to electrophilic attack.
+ Br Br + HBr
electrophile
Example: Fe
catalyst

98. c) Nucleophilic Substitution
Typical reaction of saturated organic compounds bearing polar bond as functional group, such as haloalkane with alcohol.
Example :
 
CH3CH2Br + OH-(aq) CH3CH2OH + Br-(aq)
nucleophile Δ

99. III) Elimination Reaction
An atoms or groups are removed from adjacent carbon atoms of a molecule to form a multiple bond (double or triple bond).
Results in the formation of unsaturated molecules.
Example :
CH3CH2OH conc. H2SO4 CH2= CH2 + H2O 

100. IV) Rearrangement Reaction
A reaction in which atoms or groups in a molecule change position.
Occurs when a single reactant reorganizes the bonds and atoms.
Example : H
tautomerisme H C C R H C C R H H O OH

101. Exercises
Explain how the free radicals are formed in homolytic cleavage.
2. Write an equation for the bromine-bromine bond cleavage in the bromination of methane. State the type of bond cleavage.

102. 3. Which would you expect to be the most stable free radical
3. Which would you expect to be the most stable free radical ? CH2CH3 , (CH3)2 CH , CH3 , 
CH3