1. Chapter 24 An Introduction to Organic Chemistry
24.1 What are organic compounds?
24.2 Introducing organic chemistry
24.3 Organic molecules represented by structural formulae
24.4 Saturated and unsaturated hydrocarbons
24.5 Classification of organic compounds
24.6 Naming of organic compounds
24.7 Structural formulae from IUPAC names
CONTENTS OF CHAPTER 24

2. 24.1 WHAT ARE ORGANIC COMPOUNDS?
Figure A collection of substances containing organic compounds.
WHAT ARE ORGANIC COMPOUNDS?

3. ORGANIC COMPOUNDS are carbon compounds.
CO, CO2, Na2CO3, KHCO3, H2O, NH3, KOH, HCl, HNO3, NaCl.
(Other answers may be given.)
WHAT ARE ORGANIC COMPOUNDS?

4. 24.2 INTRODUCING ORGANIC CHEMISTRY
WHAT IS ORGANIC CHEMISTRY?
ORGANIC CHEMISTRY is a branch of chemistry focusing on carbon compounds.
INTRODUCING ORGANIC CHEMISTRY

5. Figure 24.3 Organic chemistry is often studied as a separate branch of chemistry.
INTRODUCING ORGANIC CHEMISTRY

6. GENERAL CHARACTERISTICS OF ORGANIC COMPOUNDS
Constituent elements and bonding in organic compounds
Almost all organic compounds contain hydrogen besides carbon.
Most organic compounds are covalent compounds. Some consist of simple molecules. Others consist of very large molecules (macromolecules).
INTRODUCING ORGANIC CHEMISTRY

7. Most organic compounds consist of molecules:
Figure 24.4
Most organic compounds consist of molecules:
(a) Hexane consists of simple molecules (b) Starch consists of macromolecules.
INTRODUCING ORGANIC CHEMISTRY

8. Reactions of organic compounds
Tetrachloromethane CCl4.
(Other answers may be given.)
Reactions of organic compounds
In general, reactions involving organic compounds have the following in common:
 The reactions are usually slow (when compared with common inorganic reactions).
 In most cases, organic compounds can burn to give carbon dioxide and water.
INTRODUCING ORGANIC CHEMISTRY

9. Ethanol, an organic compound, burns to form carbon dioxide and water.
Figure 24.5
Ethanol, an organic compound, burns to form carbon dioxide and water.
INTRODUCING ORGANIC CHEMISTRY

10. UNIQUENESS OF CARBON
Carbon has the unique property of forming a very large number of compounds (over ). There are three reasons for this:
(1) Carbon atoms can form strong single, double and triple covalent bonds with other carbon atoms.
(2) Each carbon atom can form four single covalent bonds.
(3) Carbon can form strong bonds with other elements.
INTRODUCING ORGANIC CHEMISTRY

11. 24.2 INTRODUCING ORGANIC CHEMISTRY

12. 24.3 ORGANIC MOLECULES REPRESENTED BY STRUCTURAL FORMULAE
Table 24.1
Structures of a butane molecule and a 2-methylpropane molecule, as represented by formulae and models.
ORGANIC MOLECULES REPRESENTED BY STRUCTURAL
FORMULAE

13. Table 24.2 Structural formulae and models of some organic compounds.
ORGANIC MOLECULES REPRESENTED BY STRUCTURAL
FORMULAE

14. A24.3
ORGANIC MOLECULES REPRESENTED BY STRUCTURAL
FORMULAE

15. 24.4 SATURATED AND UNSATURATED HYDROCARBONS
Hydrocarbons may be saturated or unsaturated. Hydrocarbons containing only single bonds are said to be saturated. Those containing one or more carbon-carbon multiple bonds (C = C, C  C) are unsaturated. For example,
SATURATED AND UNSATURATED HYDROCARBONS

16. 24.5 CLASSIFICATION OF ORGANIC COMPOUNDS
FUNCTIONAL GROUP
Figure Structural formulae and models of butane, but-1-ene and butan-1-ol.
CLASSIFICATION OF ORGANIC COMPOUNDS

17. A FUNCTIONAL GROUP is an atom or group of atoms responsible for most of the chemical properties of a compound.
A24.4
(a) Yes. They have the same functional group (–OH).
(b) A < B < C < D in boiling point. Van der Waals’ forces are greater between larger molecules.
HOMOLOGOUS SERIES
The hydrocarbons methane, ethane, propane and butane belong to the same homologous series — the alkane series.
CLASSIFICATION OF ORGANIC COMPOUNDS

18. Table 24.3 Names, formulae and models of the four hydrocarbons present in natural gas.
CLASSIFICATION OF ORGANIC COMPOUNDS

19. The molecular formula is C5H12. (b) Put n = 11 in CnH2n+2.
A HOMOLOGOUS SERIES is a family of compounds all having the same general formula and with adjacent members differing by a – CH2 – unit. The individual members of a homologous series are referred to as HOMOLOGUES.
A24.5
(a) Put n = 5 in CnH2n+2.
The molecular formula is C5H12.
(b) Put n = 11 in CnH2n+2.
The molecular formula is C11H24.
CLASSIFICATION OF ORGANIC COMPOUNDS

20. Another homologous series is the alkanol (alcohol) series, with the general formula CnH2n+1OH.
Figure 24.8
Methanol and ethanol are the first two members of the alkanol series.
CLASSIFICATION OF ORGANIC COMPOUNDS

21. 24.5 CLASSIFICATION OF ORGANIC COMPOUNDS

22. Table 24.4
Some common functional groups and homologous series, with the first member in each series shown.
CLASSIFICATION OF ORGANIC COMPOUNDS

23. (a) A and C; alkanoic acid series (b) H H H H H O
H— C— C— C— C— C— C— O— H
H H H H H
CLASSIFICATION OF ORGANIC COMPOUNDS

24. 24.6 NAMING OF ORGANIC COMPOUNDS
NAMING ALKANES BY THE IUPAC SYSTEM
Naming straight-chain alkanes
All alkanes have names ending with the suffix -ane.
NAMING OF ORGANIC COMPOUNDS

25. Table 24.5 Structural formulae and names of the 10 simplest straight-chain alkanes.
NAMING OF ORGANIC COMPOUNDS

26. Alkyl groups
Alkyl groups are derived from alkanes by the removal of a hydrogen atom. They are often represented by the symbol R—.
Table Some alkyl groups and their parent alkanes.
NAMING OF ORGANIC COMPOUNDS

27. Naming branched-chain alkanes
(a) (i) Hexyl (ii) Octyl
(b) (i) CH3(CH2)3CH2—
(ii) CH3(CH2)5CH2—
Naming branched-chain alkanes
The IUPAC name for a branched-chain alkane consists of 2 parts:
(1) The prefixes which indicate the alkyl group substituents
(2) The ‘root’ which indicates the parent alkane (the main carbon chain).
NAMING OF ORGANIC COMPOUNDS

28. (alkyl groups) (main carbon chain)
That is,
Prefixes Root
(alkyl groups) (main carbon chain)
The basic IUPAC rules of naming can be illustrated by the example below:
NAMING OF ORGANIC COMPOUNDS

29. The name of the compound is:
(a) 2,3-dimethylbutane
(b) 4-ethyl-3-methylheptane
NAMING OF ORGANIC COMPOUNDS

30. NAMING HALOGEN-SUBSTITUTED ALKANES
2-bromo-1-iodo-3-methylpentane
NAMING ALKENES
Alkenes have the general formula CnH2n. We can name them with the same general rules for alkanes, but using the suffix -ene instead of -ane.
NAMING OF ORGANIC COMPOUNDS

31. For example,
NAMING OF ORGANIC COMPOUNDS

32. 24.6 NAMING OF ORGANIC COMPOUNDS

33. A24.10 (a) 2-methylbut-2-ene (b) chloroethene
NAMING OF ORGANIC COMPOUNDS

34. NAMING ALKANOLS
Alkanols have the general formula CnH2n+1OH or ROH, where R– is an alkyl group.
Names of some alkanols are given below:
CH3OH (methaneol) methanol; CH3CH2OH ethanol
CH3CH2CH2OH propan-1-ol
3 2 1
CH3CHCH propan-2-ol OH
(not propan-3-ol, as the lowest possible numeral is given to the –OH group)
NAMING OF ORGANIC COMPOUNDS

35. 1CH3—2C—3CH3 2-methylpropan-2-ol OH
(a) Butan-1-ol
(b) 4-chlorobutan-2-ol
(not 1-chlorobutan-3-ol)
NAMING OF ORGANIC COMPOUNDS

36. NAMING ALKANOIC ACIDS
Alkanoic acids have the general formula CnH2n+1COOH or
R COOH, where R– is an alkyl group or hydrogen.
Names of some alkanoic acids are given below:
HCOOH (methaneoic acid) methanoic acid
CH3COOH ethanoic acid
CH3CH2COOH propanoic acid
CH3CH2CH2COOH butanoic acid
3 2 1
CH3CHCOOH 2-methylpropanoic acid
CH3
NAMING OF ORGANIC COMPOUNDS

37. A24.12
3-chlorobutanoic acid.
NAMING OF ORGANIC COMPOUNDS

38. 24.7 STRUCTURAL FORMULAE FROM IUPAC NAMES

39. 24.7 STRUCTURAL FORMULAE FROM IUPAC NAMES

40. A24.13
24.7 STRUCTURAL FORMULAE FROM IUPAC NAMES

41. A model of butane.
24.7 STRUCTURAL FORMULAE FROM IUPAC NAMES

42. A model of but-1-ene.
24.7 STRUCTURAL FORMULAE FROM IUPAC NAMES

43. A model of butan-1-ol.
24.7 STRUCTURAL FORMULAE FROM IUPAC NAMES

44. A model of butanoic acid.
24.7 STRUCTURAL FORMULAE FROM IUPAC NAMES

45. SUMMARY 1. Organic compounds are carbon compounds.
2. Almost all organic compounds contain hydrogen besides carbon. Many contain oxygen too. They are usually covalent compounds.
3. In general, reactions involving organic compounds are slow. In most cases, organic compounds can burn to give carbon dioxide and water.
SUMMARY

46. 4. Carbon forms a very large number of organic compounds because
 carbon can form strong bonds with itself and with other elements
 each carbon atom can form 4 single covalent bonds
5. Saturated hydrocarbons are compounds (with carbon and hydrogen only) containing only single bonds.
Unsaturated hydrocarbons are compounds (with carbon and hydrogen only) containing one or more carbon-carbon multiple bonds (C=C or CC).
6. A functional group is an atom or group of atoms responsible for most of the chemical properties of a compound.
SUMMARY

47. 7. A homologous series is a family of compounds having the same general formula with adjacent members differing by a – CH2 – unit. See Table 24.4 on p. 29.
8. Organic compounds are usually named by the IUPAC system of naming. For rules and examples, refer to pp. 30 – 37.
SUMMARY