This document provides an introduction to organic chemistry, including: - Definitions of organic and inorganic compounds - Empirical, molecular, and structural formulas and how to determine them - Functional groups and homologous series that classify organic molecules - Primary, secondary, tertiary classifications of carbon atoms and related groups - Types of isomerism including structural, stereoisomerism, and examples of each

1. CHAPTER 11 : INTRODUCTION TO ORGANIC CHEMISTRY

2. CHAPTER 11 : INTRODUCTION TO ORGANIC CHEMISTRY 11.1 Introduction 11.2 Empirical molecular and structural formulas 11.3 Functional groups and homologous series 11.4 Classification of carbon atoms in organic molecules 11.5 Isomerism 11.6 Reactions in organic compound

4. Some examples of carbon compounds in our daily lives :- methane (a component of natural gas) Methyl salicylic acid (aspirin-a drug) alanine (amino acid-a protein component) cocaine (a pain killer)

6. Quantitative example :- A sample of hydrocarbon contains 85.7 % carbon and 14.3 % hydrogen by mass. Its molar mass is 56. Determine the empirical formula and molecular formula of the compound.

7. Solution :- = 7.142 = 14.3  Empirical formula = CH 2 n (empirical molar mass)= molar mass n ( 12 x 1 + 1 x 2 ) = 56 n = 4 Molecular formula = C 4 H 8 14.43 7.142 = 2 7.142 7.142 = 1 Smallest ratio 14.3 1.0 85.7 12.0 Moles (n) 14.3 85.7 Mass (g) H C Element

11. Example : C 4 H 9 Cl CH 3 CHCH 2 CH 3 or CH 3 CH(Cl)CH 2 CH 3 Condensed structure Cl

14. 2. = CH 2 =CHCH 2 OH 3. = OH

15. Practice Exercise : Rewrite each of the following structures using skeletal formula :- (CH 3 ) 2 CHCH 2 CH 2 CH(CH 3 )CH 2 CH 3 CH 2 = CHCH 2 CH 2 CH = CHCH 3 1. 2. 3. 4.

16. d) 3 - Dimensional formula (wedge - dashed wedge - wedge) Describes how the atoms of a molecule are arranged in space Example : (Bromoethane) Indication :- bonds that lie in the plane of the page bonds that lie behind the plane bonds that project out of the plane of the paper OR OR

18. Example : 2 – butanol , CH 3 CH(OH)CH 2 CH 3 OR

20. Some important functional groups in organic compounds :- CH  CH ethyne -yne C n H 2n-2 C  C (triple bond) alkynes CH 2 =CH 2 ethene -ene C n H 2n C = C (double bond) alkene CH 4 methane -ane C n H 2n+2 none alkane Example IUPAC nomenclature Prefix- -suffix General Formula Functional Group Homologous Series

21. aromatic ring methylbenzene CH 3 CH 2 Cl chloroethane haloalkane C n H 2n+1 X – X (halogen) haloalkane CH 3 OCH 3 methoxymethane alkoxyalkane C n H 2n+2 O – OR (alkoxy) ether CH 3 CH 2 OH ethanol alkanol C n H 2n+1 OH – OH (hydroxyl) alcohol -benzene C n H 2n-6 arene Example IUPAC nomenclature Prefix- -suffix General Formula Functional Group Homologous Series

22. carbonyl H ethanal carbonyl CH 3 propanone C OH O carboxyl OH ethanoic acid CH 3 C=O alkanoic acid CnH 2n O 2 carboxylic acid CH 3 C=O alkanone C n H 2n O ketone CH 3 C=O alkanal C n H 2n O aldehyde Example IUPAC nomenclature Prefix- -suffix General Formula Functional Group Homologous Series

23. acyl Cl ethanoyl chloride ester ethyl ethanoate amide ethanamide amino methanamine CH 3 NH 2 -amine C n H 2n+1 NH 2 -NH 2 amine CH 3 CONH 2 -amide C n H 2n+1 CONH 2 amide CH 3 COOCH 3 alkyl alkanoate C n H 2n O 2 ester CH 3 C=O alkanoyl chloride C n H 2n+1 COCl acyl chloride Example IUPAC nomenclature Prefix- -suffix General Formula Functional Group Homologous Series

31. 1 ° alkyl chloride 1 ° C 2 ° alkyl chloride 2 ° C 3 ° alkyl chloride 3 ° C

33. 1 ° alcohol 1 ° C 2 ° C 2 ° alcohol 3 ° alcohol 3 ° C

35. N bonded to one alkyl group A primary (1°) amine N bonded to two alkyl group A secondary (2°) amine N bonded to three alkyl group A tertiary (3°) amine

36. ISOMERISM Structural/Constitutional Isomerism Stereoisomerism Isomerism Chain isomerism Positional isomerism Functional group isomerism Geometric isomerism Optical isomerism

41. 1,2-dimethylbenzene iii) C 8 H 10 CH 3 CH 3 CH 3 CH 3 1,3-dimethylbenzene CH 3 CH 3 1,4-dimethylbenzene

43. Example : i) C 2 H 6 O CH 3 CH 2 OH ethanol CH 3 OCH 3 dimethyl ether ii) C 3 H 6 O CH 3 CH 2 C-H O propanal CH 3 C-CH 3 O propanone iii) C 3 H 6 O 2 CH 3 CH 2 C-OH O propanoic acid CH 3 C-O-CH 3 O methyl ethanoate

46. Examples : H 3 C CH 3 H H C C = i) cis -2-butene H 3 C C = C CH 3 H H trans -2-butene ii) H 3 C CH 2 CH 3 C = C H CH 3 trans -3-methyl-2-pentene H 3 C CH 3 C = C H CH 2 CH 3 cis -3-methyl-2-pentene

47. iii) H H CH 3 CH 3 cis -1,2-dimethylcyclohexane H H CH 3 CH 3 trans -1,2-dimethylcyclohexane Cl Cl H H iv) Cl Cl H H cis -1,3-dichlorocyclopentane trans -1,3-dichlorocyclopentane

51. Schematic representation of a polarimeter containing an optically active sample : clockwise rotation – plus sign (+) / dextrorotarory anticlockwise rotation – minus sign (-) / levorotorary

54. ii) 2-hydroxypropanoic acid, CH 3 CHCOOH OH :- COOH COOH OH HO H H CH 3 CH 3 enantiomers

57. Example : The 4 stereoisomers of 2-amino-3-hydroxybutanoic acid CH3CH-CHCOOH are shown below using OH NH 2 Fischer projection formula:- COOH COOH CH 3 CH 3 H H H H NH 2 H 2 N OH HO enantiomers COOH NH 2 H H HO CH 3 COOH H H OH H 2 N enantiomers CH 3 A B C D Four pairs of diastereomers are identified : A and C ; A and D ; B and C ; B and D

59. Example : Tartaric acid , HOOCCH(OH)CH(OH)COOH COOH OH OH H H COOH COOH COOH HO HO H H COOH COOH H H OH OH plane of symmetry plane of symmetry rotate 180 o P Q identical

61. COOH OH OH H H COOH COOH COOH R S COOH COOH H HO H OH * not a plane of symmetry * not a plane of symmetry rotate 180 o different H OH H HO

83. 2. Substitution Reaction A reaction in which an atom or group in a molecule is replaced by another atom or group a) Free-radical Substitution b) Electrophilic Substitution c) Nucleophilic Substitution