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Introduction to Organic Chemistry

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  1. Chapter 24 Introduction to Organic Chemistry 24.1What is Organic Chemistry? 24.2The Unique Nature of Carbon 24.3Classification of Organic Compounds

  2. 24.1 What is Organic Chemistry (SB p.2) Organic Chemistry:The chemistry of the compounds ofcarbon • Carbon compounds: DNA, proteins in our body, carbohydrates, wool, cotton, petrol, medicines, pesticides, etc. • Organic chemicals • make our life easy • but also cause serious environmental problems • (e.g. organic compounds used as aerosol propellent damage the ozone layer, insecticide is harmful to human

  3. 24.1 What is Organic Chemistry (SB p.3) Inorganic Compounds Organic Compounds obtained from living organisms obtained from non-living sources Development of Organic Chemistry as a Science In the past …, Chemistry

  4. 24.1 What is Organic Chemistry (SB p.3) In 1828, Wohler (a German chemist) (Inorganic compound) (Organic compound) Redefining …... Organic chemistry is the study of carbon compounds except carbon monoxide, carbon dioxide, carbonates, hydrogencarbonates, carbides and cyanide.

  5. 24.1 What is Organic Chemistry (SB p.4) Fractional distillation / destructive distillation Natural Sources of Organic Compounds Alkanes / Alkenes / Alkynes / Aromatic hydrocarbons Crude oil / coal Carbohydrates / Proteins / Fats / Vitamins / Antibiotics Living things

  6. 24.2 The Unique Nature of Carbon (SB p.5) Ability to Catenate Carbon atoms can link themselves together to form chains of varying length, branched chains and rings of different sizes Catenation: The ability of atoms in forming stable bonds with itself and joining up in chains or rings. e.g.

  7. 24.2 The Unique Nature of Carbon (SB p.5) Carbon (ground state) Carbon (excited state) Ability to Form Multiple Bonds • Electronic configuration of carbon (ground state) : 1s22s22p2 • Each carbon atom has four unpaired electrons when excited • tend to form 4 covalent bonds

  8. 24.2 The Unique Nature of Carbon (SB p.6)

  9. 24.2 The Unique Nature of Carbon (SB p.6) Example 24-1 Would you expect silicon, which is just below carbon in the Periodic Table, to catenate to form diverse molecular structures? Explain your answer. Answer Solution: Silicon, unlike carbon, does not catenate to form diverse molecular structures. Carbon is able to catenate because carbon atoms have a relatively small atomic size. This enables a carbon atom to form strong covalent bonds with other carbon atoms. However, due to the greater atomic size of silicon, its ability to catenate is much lower than that of carbon.

  10. 24.2 The Unique Nature of Carbon (SB p.7) The electronic configuration of sulphur is 1s22s22p63s23p4. It has only two unpaired electrons. Its atomic size is larger than that of carbon. So it has a much lower tendency to catenate than carbon. Check Point 24-1 Would you expect sulphur, which has an electronegativity value very close to carbon, to catenate? Why? Answer

  11. 24.3 Classification of Organic Compounds (SB p.7) Functional Groups The compounds in a particular family are characterized by the presence of a certain arrangement of atoms called a functional group A functional group is defined as an atom or a group of atoms that effectively determines the chemical properties of an organic compound.

  12. 24.3 Classification of Organic Compounds (SB p.7) and e.g. have similar chemical properties because they contain the same functional group –OH. They are classified into the same homologous series — Alcohols.

  13. 24.3 Classification of Organic Compounds (SB p.8) R = CnH2n+1 –

  14. 24.3 Classification of Organic Compounds (SB p.8) R = CnH2n+1 –

  15. 24.3 Classification of Organic Compounds (SB p.8) R = CnH2n+1 –, X = F, Cl, Br or I

  16. 24.3 Classification of Organic Compounds (SB p.9) R = CnH2n+1 –

  17. 24.3 Classification of Organic Compounds (SB p.9) Number of carbon atom(s) IUPAC name Molecular formula Condensed structural formula Structural formula 1 Methane CH4 CH4 2 Ethane C2H6 CH3CH3 3 Propane C3H8 CH3CH2CH3 4 Butane C4H10 CH3CH2CH2CH3 A homologous series is a series of compounds that have the same functional group, and each member differs from the next member by a – CH2 – unit in their formulae.

  18. 24.3 Classification of Organic Compounds (SB p.10)

  19. 24.3 Classification of Organic Compounds (SB p.10) Chemical properties Members in the same series can be represented by a general formula. e.g. General formula of alkanes: CnH2n+2 General formula of alcohols: CnH2n+1OH Functional group of an organic compound Members of a homologous series have similar chemical properties

  20. 24.3 Classification of Organic Compounds (SB p.10) The physical properties change gradually along the homologous seriese.g. the longer the carbon chain in molecule ( or the greater the molecular mass) the greater the attractive force between molecules  the higher the melting point and boiling point

  21. 24.3 Classification of Organic Compounds (SB p.11) Some physical properties of the first 20 members of straight-chain alkanes

  22. 24.3 Classification of Organic Compounds (SB p.11) Some physical properties of the first 20 members of straight-chain alkanes

  23. 24.3 Classification of Organic Compounds (SB p.11) Solution: (a) Carbon-carbon double bond ( ) and chloro ( ) group Example 24-2 Identify the functional group(s) in the following compound: (a) Answer

  24. 24.3 Classification of Organic Compounds (SB p.11) Solution: (b) Carbonyl group ( ) Example 24-2 Identify the functional group(s) in the following compound: (b) Answer

  25. 24.3 Classification of Organic Compounds (SB p.12) Solution: (c) Amino group ( ) and carboxyl group ( ) Example 24-2 Identify the functional group(s) in the following compound: (c) Answer

  26. 24.3 Classification of Organic Compounds (SB p.12) Example 24-3 To which homologous series does each of the following compounds belong? (a) Solution: (a) Ester Answer

  27. 24.3 Classification of Organic Compounds (SB p.13) Example 24-3 To which homologous series does each of the following compounds belong? (b) Solution: (b) Amide Answer

  28. 24.3 Classification of Organic Compounds (SB p.13) Example 24-3 To which homologous series does each of the following compounds belong? (c) Solution: (c) Acid anhydride Answer

  29. 24.3 Classification of Organic Compounds (SB p.13) Example 24-4 State whether each of the following pairs of compounds belongs to the same homologous series. Explain your answers. (a) Answer Solution: (a) No, the first one is a carboxylic acid and the second one is an ester.

  30. 24.3 Classification of Organic Compounds (SB p.13) Example 24-4 State whether each of the following pairs of compounds belongs to the same homologous series. Explain your answers. (b) Answer Solution: (b) Yes, both of them are alcohols.

  31. 24.3 Classification of Organic Compounds (SB p.13) Example 24-4 State whether each of the following pairs of compounds belongs to the same homologous series. Explain your answers. (c) Answer Solution: (c) No, the first one is an amide and the second one is an amine.

  32. 24.3 Classification of Organic Compounds (SB p.14) (a) Alcohol, ether, aldehyde, ketone, carboxylic acid, ester, acyl halide, amide and acid anhydride Check Point 24-2 (a) Name the homologous series of organic compounds that contain the element oxygen in their functional groups. Answer

  33. 24.3 Classification of Organic Compounds (SB p.14) (b) – OH (hydroxyl) and – O – (oxy) groups Check Point 24-2 (b) Identify and name the functional groups in glucose which has the structure: Answer

  34. 24.3 Classification of Organic Compounds (SB p.14) (c) – Br (bromo), (aldehyde), (acyl chloride) and (carbon-carbon double bond) group Check Point 24-2 (c) Identify and name the functional groups in the following compound: Answer

  35. The END