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Chapter 24 An Introduction to Organic Chemistry

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.

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Chapter 24 An Introduction to Organic Chemistry

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

  2. 24.1 WHAT ARE ORGANIC COMPOUNDS? Figure 24.2 A collection of substances containing organic compounds. 24.1 WHAT ARE ORGANIC COMPOUNDS?

  3. ORGANIC COMPOUNDS are carbon compounds. A24.1 CO, CO2, Na2CO3, KHCO3, H2O, NH3, KOH, HCl, HNO3, NaCl. (Other answers may be given.) 24.1 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. 24.2 INTRODUCING ORGANIC CHEMISTRY

  5. Figure 24.3 Organic chemistry is often studied as a separate branch of chemistry. 24.2 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). 24.2 INTRODUCING ORGANIC CHEMISTRY

  7. Figure 24.4 Most organic compounds consist of molecules: (a) Hexane consists of simple molecules. (b) Starch consists of macromolecules. 24.2 INTRODUCING ORGANIC CHEMISTRY

  8. A24.2 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. 24.2 INTRODUCING ORGANIC CHEMISTRY

  9. Figure 24.5 Ethanol, an organic compound, burns to form carbon dioxide and water. 24.2 INTRODUCING ORGANIC CHEMISTRY

  10. UNIQUENESS OF CARBON Carbon has the unique property of forming a very large number of compounds (over 4 000 000). 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. 24.2 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. 24.3 ORGANIC MOLECULES REPRESENTED BY STRUCTURAL FORMULAE

  13. Table 24.2 Structural formulae and models of some organic compounds. 24.3 ORGANIC MOLECULES REPRESENTED BY STRUCTURAL FORMULAE

  14. A24.3 24.3 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, 24.4 SATURATED AND UNSATURATED HYDROCARBONS

  16. 24.5CLASSIFICATION OF ORGANIC COMPOUNDS FUNCTIONAL GROUP Figure 24.7 Structural formulae and models of butane, but-1-ene and butan-1-ol. 24.5 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. 24.5 CLASSIFICATION OF ORGANIC COMPOUNDS

  18. Table 24.3 Names, formulae and models of the four hydrocarbons present in natural gas. 24.5 CLASSIFICATION OF ORGANIC COMPOUNDS

  19. 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. 24.5 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. 24.5 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. 24.5 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 A24.6 24.5 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. 24.6 NAMING OF ORGANIC COMPOUNDS

  25. Table 24.5 Structural formulae and names of the 10 simplest straight-chain alkanes. 24.6 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 24.6 Some alkyl groups and their parent alkanes. 24.6 NAMING OF ORGANIC COMPOUNDS

  27. A24.7 (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). 24.6 NAMING OF ORGANIC COMPOUNDS

  28. That is, Prefixes Root (alkyl groups) (main carbon chain) The basic IUPAC rules of naming can be illustrated by the example below: 24.6 NAMING OF ORGANIC COMPOUNDS

  29. The name of the compound is: A24.8 (a) 2,3-dimethylbutane (b) 4-ethyl-3-methylheptane 24.6 NAMING OF ORGANIC COMPOUNDS

  30. NAMING HALOGEN-SUBSTITUTED ALKANES A24.9 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. 24.6 NAMING OF ORGANIC COMPOUNDS

  31. For example, 24.6 NAMING OF ORGANIC COMPOUNDS

  32. 24.6 NAMING OF ORGANIC COMPOUNDS

  33. A24.10 (a) 2-methylbut-2-ene (b) chloroethene 24.6 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 3 2 1 CH3CH2CH2OH propan-1-ol 3 2 1 CH3CHCH3 propan-2-ol OH (not propan-3-ol, as the lowest possible numeral is given to the –OH group) 24.6 NAMING OF ORGANIC COMPOUNDS

  35. CH3 1CH3—2C—3CH3 2-methylpropan-2-ol OH A24.11 (a) Butan-1-ol (b) 4-chlorobutan-2-ol (not 1-chlorobutan-3-ol) 24.6 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 24.6 NAMING OF ORGANIC COMPOUNDS

  37. A24.12 3-chlorobutanoic acid. 24.6 NAMING OF ORGANIC COMPOUNDS

  38. 24.7 STRUCTURAL FORMULAE FROM IUPAC NAMES 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 compoundsare 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 hydrocarbonsare compounds (with carbon and hydrogen only) containing only single bonds. Unsaturated hydrocarbonsare compounds (with carbon and hydrogen only) containing one or more carbon-carbon multiple bonds (C=C or CC). 6. Afunctional groupis an atom or group of atoms responsible for most of the chemical properties of a compound. SUMMARY

  47. 7. Ahomologous seriesis 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

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