1. Chapter 25 Organic Chemistry

2. 25.1
Why Carbon is Different?
25.2
Organic Compounds (groups, functional groups, naming etc.)
25.3
Representing Organic Molecules
25.4
Isomerism
25.5
Organic Reactions (Omitted)
25.6
Organic Polymers (Biopolymer section is omitted)

3. What is Organic Chemistry?
10.1
Organic chemistry is the field of science that studies the structure, properties, composition of hydrocarbons (compounds containing carbon and hydrogen). These compounds may contain some other elements, including oxygen, nitrogen and halogens.
Glucose molecule
Fat molecule

4. Why Carbon is Different
10.1
All known INORGANIC compounds ~100,000
ORGANIC compounds, MILLIONS
Electron configuration: [He]2s22p2 shows that C atom effectively prohibits ion formation and tends to share electrons.
Carbon atom has a small atomic radius which gives rise to short and strong carbon bonds and, hence, stable compounds. (14Si?? in the same group..)
C atoms can form σ and strong π bonds.

5. These attributes enable carbon to form chains (straight, branched, and cyclic) containing single, double, and triple carbon-carbon bonds. Carbon’s formation of chains is called catenation.

6. Aromatic Compounds
Organic compounds that are related to benzene, or that contain one or more benzene rings, are called aromatic compounds.

7. Aliphatic Compounds
Organic molecules that do not contain the benzene ring are called aliphatic compounds.

8. 10.2
Alkanes
Alkanes are simple organic compounds that consist of only carbon and hydrogen. They contain only single bonds.
General Formula
CnH2n+2
CH4
Methane
C2H6
Ethane
C3H8
Propane
C4H10
Butane
C5H12
Pentane

9. Alkanes General Formula CnH2n+2 C6H14 Hexane C7H16 Heptane C8H18
10.2
Alkanes
C6H14
Hexane
General Formula
CnH2n+2
C7H16
Heptane
C8H18
Octane
C9H20
Nonane
C10H22
Decane

10. 10.2
Alkyl Groups
An alkyl group (R) is a portion of a molecule that resembles an alkane. An alkyl group is formed by removing one hydrogen atom from the corresponding alkane.
Alkyl groups are represented in organic compounds with R.
Methyl
Ethyl
Propyl
Isopropyl

11. Alkyl Groups
10.2
Butyl
tert-Butyl
Pentyl
Isopentyl
Hexyl
Heptyl
Octyl

12. Substituents/groups
F – Fluoro
Cl – Chloro
Br – Bromo
I - Iodo

13. Functional Groups
10.2
A functional group is a group of atoms that determines many of the molecule’s properties, and that are responsible for chemical reactions.
Some commonly important functional groups:
Alcohol
Carboxylic acid
Aldehydes
Esters
Ketone
Amines
Amides

14. Functional Groups R represents an alkyl group.
10.2
Functional Groups
Alcohol
Carboxylic acid
Ester
Aldehyde
Ketone
R represents an alkyl group.
R’ represents a second alkyl group that may or may not be identical to the first alkyl group R.

15. Functional Groups
10.2
Amine
Amine
Amine
Amide
Amide
Amide
1, 2 and 3 indicate one, two, and three R groups bonded to the N atom, respectively

16. Identifying Functional Groups
10.2
R-COOH
Carboxylic acid
R-NH2
1 amine
R-CO-H
Aldehyde
R-OH
Alcohol

17. Identifying Functional Groups
10.2
Identifying Functional Groups
R-CO-R’
Ketone
R-COOH
Carboxylic Acid

18. Identifying Functional Groups
10.2

19. Identifying Functional Groups

20. Naming Organic Compounds
Molecular formula is not enough as the properties of organic
compounds vary significantly depending on the group and
functional group position..
Hexane (C6H14)

21. Naming Organic Compounds
10.2
Organic compounds are named using the “International Union of Pure and Applied Chemistry” (IUPAC) rules.
There are:
Systematic names: names that are based on IUPAC system.
Trivial names: names that are commonly used but are not based on IUPAC system. F F
Systematic Name
Trichloromethane
Dichlorodifluoromethane
Trivial Name
Chloroform
Freon

22. Naming Organic Compounds (Nomenclature)
10.2
How to name alkanes.
Identify the longest continuous carbon chain to get the parent name.
Number the carbons in the continuous chain, beginning at the end closest to the substituent.
Identify the substituent and use a number and a prefix to specify location and identity, respectively.
methyl at position 3
hexane 1 2 3 4 5 6
3-Methylhexane

23. Naming Organic Compounds
10.2
How to name alkanes.
When two or more substituents are there:
If they are identical, use prefixes (di, tri, tetra, …) to indicates the number of substituents.
Also, use numbers as usual to indicate which C atom they are bonded to.
methyl 1 2 3 4 5 6
methyl
3,3-Dimethylhexane

24. 3-Ethyl-2-methylhexane
10.2
If the carbon number is same in 2 chains, choose the chain with more substituents
How to name alkanes.
When two or more substituents are there:
If the substituents are not identical, follow the same procedure for identical substituents. However, the substituent names must be put in an alphabetical order. (prefixes are not used to determine the alphabetization)
methyl 1 2 3 4 5 6
ethyl
3-Ethyl-2-methylhexane
Notice that incorrect numbering would lead to the name 3-isopropylhexane.

25. Naming Organic Compounds
10.2
Naming Organic Compounds
Exercise:
Name the following organic compounds:
2-Chloro-3-methylpentane
3-Ethyl-3-methylheptane

26. Naming Organic Compounds Containing Functional Groups
10.2
How to name alcohols.
Identify the longest chain that includes the –OH group.
Do numbering such that the C bearing –OH group is given the lowest number.
Change the –e ending to -ol.
If the chain also contains an alkyl substituent, give the –OH group the lowest number.
alcohol 4 3 2 1
1-Butanol
Butane
3-Methyl-1-butanol

27. What we discussed in last lecture
Organic chemistry
How C is different
Aromatic & aliphatic compounds
Alkane
Alkyl groups & substituents
Functional groups
Naming organic compounds

28. Today… Organic Compounds (groups, functional groups, naming etc.)
Representing Organic Molecules
Isomerism

29. Containing Carboxy Groups
10.2
How to name carboxylic acids.
Identify the longest chain that includes the carboxy group.
Do numbering starting with the carbonyl (C=O) carbon.
Change the – e ending to – oic acid.
Use numbers and prefixes to indicate the position and identity of any substituents. 4 3 2 1
Carboxylic acid
Butanoic acid 3 2 1 4 5
3-Fluoro-3-methyl-pentanoic acid

30. Naming Organic Compounds Containing Functional Groups
10.2
What is the name of the carboxylic acids shown below? Br
Ethanoic acid
Bromoethanoic acid
Acetic acid
Bromoacetic acid
Trivial name

31. Naming Organic Compounds Containing Functional Groups
10.2
Ester group
How to name esters.
Esters are named as derivatives of carboxylic acids by:
locating the ester group.
locating the main carbon chain which is the R group connected to the C=O group.
locating the substituent.
replacing the –ic acid ending with – oate. 4 3 2 1
Methyl butanoate
Ester group
Propyl ethanoate
Trivial name
Propyl acetate

32. Naming Organic Compounds Containing Functional Groups
10.2
Aldehyde
How to name aldehydes.
Identify the longest chain that includes the carbonyl group.
Change the –e ending to - al.
Number starting with the carbonyl (C=O) carbon.
Use numbers and prefixes to indicate the position and identity of any substituents. 3 2 1
Propanal 1 2 3 4 5
2,5-Dichloro-2-ethylpentanal

33. Naming Organic Compounds Containing Functional Groups
10.2
Naming Organic Compounds Containing Functional Groups
How to name ketones.
Identify the longest chain that includes the carbonyl group.
Number to give the carbonyl group (C=O) the lowest possible number.
Change the –e ending to - one.
Use numbers and prefixes to indicate the position and identity of any substituents.
Carbonyl 4 3 2 1
2-Butanone 4 5 6 7 8 3 2 1
8-Iodo-2-methyl-4-octanone

34. Naming Organic Compounds Containing Functional Groups
10.2
Amine
How to name primary amines.
Identify the longest chain that includes the –NH2 group.
Number C atoms so that the C atom to which the –NH2 group is bonded is given the lowest possible number.
Change the –e ending to - amine.
Use numbers and prefixes to indicate the position and identity of any substituents. 2 1
Ethanamine 5 4 3 2 1
1-Pentanamine 5 4 3 2 1
1,5,5-Trichloro-2-pentanamine

35. Naming Organic Compounds Containing Functional Groups
10.2
Amide
How to name primary amides.
Primary amides can be named as derivatives of carboxylic acids by replacing the –ic acid ending with – amide. 3 2 1
Propanamide 6 5 4 3 2 1
4-Fluoro-5-methylhexanamide

36. Naming Organic Compounds
10.2
Naming Organic Compounds
Exercise: 4 5 6 7 4 5 8 1 2 3 3 6 9 2 7 10 8 1
4-ethyl-7-methyl-5-propyldecane
4-ethyl-5-propyloctane

37. Representing Organic Molecules
Condensed Structural Formulas
Kekulé Structures
Skeletal Structures
Resonance

38. Representing Organic Molecules
Condensed Structural Formulas
A condensed structural formula, or simply a condensed structure, shows the same information as a structural formula, but in a condensed form.

39. Representing Organic Molecules
Condensed Structural Formulas

40. Representing Organic Molecules
10.3
Representing Organic Molecules
Kekulé structure
Kekulé structure: It is similar to Lewis structure but without showing the lone pairs. It is very commonly used in organic chemistry.
Kekulé structure

41. Representing Organic Molecules
Kekulé structure

42. Representing Organic Molecules
Skeletal structure

43. When a heteroatom is present?
Skeletal structure

44. Representing Organic Molecules
10.3
Exercise:
Write a molecular formula and condensed structural formula for the following:
C4H8
C2H5NO
Molecular formula
Molecular formula
CH3(CH)2CH3
CH3CONH2
Cond. Structural formula
Cond. Structural formula

45. Representing Organic Molecules
10.3
Exercise:
Write the molecular formula and a structural formula for the following molecule. O
CH3COCH2CH3
Structural formula
C4H8O
Molecular formula
What is the correct name of this compound?
2-butanone

46. 10.3
Resonance
Resonance is repositioning of electrons to produce other equivalent structures of the molecule.
You will need to review how to draw Lewis structures for simple organic compounds.
Example: Draw the Lewis structure of nitrate ion (NO3‒) and show resonance structure. N 1– O

47. 10.3
Resonance
The nitrate ion structure is the average of all the three equivalent structures, not one of them.
The three NO bonds are found from experiments to be identical.
Resonance structures: 1– 1– 1– O O O N N N O O O O O O

48. More Examples on Resonance Structures
10.3
More Examples on Resonance Structures
The anion produced from ethanoic acid (ethanoate).
Benzene molecule (C6H6)

49. Why acetic acid loses protons much more easily than alcohol??

51. ISOMERISM
Isomers are molecules that have the same molecular formula, but have a different arrangement of the atoms in space.
Excludes any different arrangements which are simply due to the molecule rotating as a whole, or rotating about particular bonds.

52. Constitutional or Structural Isomerism
25.4
ISOMERISM
Constitutional or Structural Isomerism
Stereoisomerism
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53. ISOMERISM 25.4 Constitutional Isomerism
Constitutional isomerism occurs when the same atoms can be connected in two or more different ways.
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54. ISOMERISM 25.4 Constitutional Isomerism 54
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55. How many structural isomers hexane (C6H14) has,
draw the structure?

56. ISOMERISM Stereoisomerism
Stereoisomers are those that contain identical bonds but differ in the orientation of those bonds in space.
Two types of stereoisomers exist: geometrical isomers and optical isomers.
Geometrical isomers occur in compounds that have restricted rotation around a bond.
Stereoisomers that are mirror images of each other, but are not superimposable, are called optical isomers.
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57. ISOMERISM 25.4 Stereoisomerism (Geometrical Isomerism)
Structural isomer
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58. ISOMERISM 25.4 Stereoisomerism (Optical Isomerism) 58
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59. ISOMERISM 25.4 Stereoisomerism (Optical Isomerism)
Molecules with nonsuperimposable mirror images are called chiral; and a pair of such mirror-image molecules are called enantiomers.
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61. 25.4
ISOMERISM
Representing three-dimensional objects on two-dimensional surface
it often is necessary to represent tetrahedral molecules (three- dimensional objects) on paper (a two-dimensional surface).
This is done using dashes
to represent bonds that
point behind the page,
and wedges to represent
bonds that point in front
of the page.
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62. ISOMERISM 25.4 Determination of chirality or enantiomers
One property of chiral molecules is that the two enantiomers rotate the plane of plane-polarized light in opposite directions; that is, they are optically active.
If the plane of polarization is rotated to the right, the isomer is said to be dextrorotatory and is labeled d; if it is rotated to the left, the isomer is called levorotatory and labeled l.
Enantiomers always rotate the light by the same amount, but in opposite directions. Thus, in an equimolar mixture of both enantiomers, called a racemic mixture, the net rotation is zero.
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63. 25.4 Isomerism Stereoisomerism 63
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64. Condensation Polymers
Addition Polymers
Condensation Polymers

65. 25.6 Organic Polymers Addition Polymers
Polymers are molecular compounds, either natural or synthetic, that are made up of many repeating units called monomers.
Addition polymers form when monomers such as ethylene join end to end to make polyethylene.
Reactions of this type can be initiated by a radical—a species that contains an unpaired electron.
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66. 25.6 Organic Polymers Addition Polymers 66
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67. 25.6 Organic Polymers Addition Polymers 67
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68. 25.6 Organic Polymers Addition Polymers 68
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69. 25.6 Organic Polymers Condensation Polymers
Reactions in which two or more molecules become connected with the elimination of a small molecule, often water, are called condensation reactions.
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70. 25.6 Organic Polymers Condensation Polymers
Condensation polymers form when molecules combine through functional groups with the elimination of a small molecule, often water.
Many condensation polymers are copolymers, meaning that they are made up of two or more different monomers.
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71. 25.6 Organic Polymers Condensation Polymers 71
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72. Exercise
Draw the structure of polypropylene, showing atleast 2 repeating
units.
Draw the structure of monomer used to make the below polymer.
Polymethyl methacrylate

73. Draw the structure of monomer used to make the below polymer.

74. Answers
monomer n
monomer

75. Answers
monomer
monomer
polymer