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Introduction to Organic Chemistry

21. Introduction to Organic Chemistry. 21.1 What is Organic Chemistry? 21.2 The Unique Nature of Carbon 21.3 Classification of Organic Compounds 21.4 Factors Affecting the Physical Properties of Organic Compounds. 21.1. What is Organic Chemistry?.

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Introduction to Organic Chemistry

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  1. 21 Introduction to Organic Chemistry 21.1 What is Organic Chemistry? 21.2 The Unique Nature of Carbon 21.3 Classification of Organic Compounds 21.4 Factors Affecting the Physical Properties of Organic Compounds

  2. New Way Chemistry for Hong Kong A-Level 3A 21.1 What is Organic Chemistry?

  3. New Way Chemistry for Hong Kong A-Level 3A 21.1 What is Organic Chemistry (SB p.2) Organic Chemistry • Chemistry of the compounds present in living organisms. • They all contain carbon. • Organic Chemistry is the Chemistry of Carbon.

  4. New Way Chemistry for Hong Kong A-Level 3A A variety of organic products obtained from living things 21.1 What is Organic Chemistry (SB p.4) Natural Sources of Organic Compounds Carbohydrates / Proteins / Fats / Vitamins / Antibiotics Living things

  5. New Way Chemistry for Hong Kong A-Level 3A Fractional distillation / destructive distillation Check Point 21-1 A variety of useful products derived from crude oil and coal 21.1 What is Organic Chemistry (SB p.4) Natural Sources of Organic Compounds Alkanes / Alkenes / Alkynes / Aromatic hydrocarbons Crude oil or coal

  6. New Way Chemistry for Hong Kong A-Level 3A Inorganic compounds Organic compounds obtained from living organisms obtained from non-living sources 21.1 What is Organic Chemistry (SB p.3) Development of Organic Chemistry as a Science In the past …, Chemistry

  7. New Way Chemistry for Hong Kong A-Level 3A 21.1 What is Organic Chemistry (SB p.3) Development of Organic Chemistry as a Science In 1828, Wohler (a German chemist) (Inorganic compound) (Organic compound)

  8. New Way Chemistry for Hong Kong A-Level 3A 21.1 What is Organic Chemistry (SB p.3) Development of Organic Chemistry as a Science Redefining … ... Organic chemistry is the study of carbon compounds (except CO,CO2, carbonates, hydrogencarbonates, carbides and cyanides) obtained from natural sources or synthesized in the laboratories.

  9. New Way Chemistry for Hong Kong A-Level 3A 21.2 The Unique Nature of Carbon

  10. New Way Chemistry for Hong Kong A-Level 3A Carbon (ground state) 21.2 The Unique Nature of Carbon (SB p.5) Ability to form four strong covalent bonds • Electronic configuration of carbon (ground state) : 1s22s22p2

  11. New Way Chemistry for Hong Kong A-Level 3A Carbon (excited state) 21.2 The Unique Nature of Carbon (SB p.5) Ability to form four strong covalent bonds • Each carbon atom has four unpaired electrons when excited • Tend to form four strong covalent bonds

  12. New Way Chemistry for Hong Kong A-Level 3A 21.2 The Unique Nature of Carbon (SB p.5) Ability to Catenate • Carbon atoms link together to form chains of varying length, branched chains and rings of different sizes • Catenation: •  Ability of atoms in forming stable bonds with itself, hence joining up into chains or rings

  13. New Way Chemistry for Hong Kong A-Level 3A 21.2 The Unique Nature of Carbon (SB p.5) Ability to Catenate C – C > Si – Si > Ge – Ge > Sn – Sn Bond strength  as bond length 

  14. New Way Chemistry for Hong Kong A-Level 3A 21.2 The Unique Nature of Carbon (SB p.5) Ability to Catenate C – C > N – N > O – O Bond strength  as the number of lone pairs 

  15. New Way Chemistry for Hong Kong A-Level 3A 21.2 The Unique Nature of Carbon (SB p.5) Ability to Catenate CnH2n+2 n = 1,2,3,…(no limit for n) SinH2n+2 n = 1 to 6 only  silanes GenH2n+2 n = 1 to 3 only  germanes SnnH2n+2 Only SnH4 (stannane) exists

  16. New Way Chemistry for Hong Kong A-Level 3A 4 bonds sp2 sp3 sp 1 bond, 3 bonds 2 bonds, 2 bonds Carbon (excited state) 21.2 The Unique Nature of Carbon (SB p.5) Ability to Form Multiple Bonds

  17. New Way Chemistry for Hong Kong A-Level 3A 21.2 The Unique Nature of Carbon (SB p.6) * X = halogens

  18. New Way Chemistry for Hong Kong A-Level 3A Example 21-2 Check Point 21-2 21.2 The Unique Nature of Carbon (SB p.6)

  19. New Way Chemistry for Hong Kong A-Level 3A 21.3 Classification of Organic Compounds

  20. New Way Chemistry for Hong Kong A-Level 3A 21.3 Classification of Organic Compounds (SB p.7) Functional Groups • Organic compounds are classified by the the presence of characteristic functional groups.

  21. New Way Chemistry for Hong Kong A-Level 3A 21.3 Classification of Organic Compounds (SB p.7) Functional Groups A functional group is defined as an atom or a group of atoms that effectively determines the chemical properties of an organic compound.

  22. New Way Chemistry for Hong Kong A-Level 3A 21.3 Classification of Organic Compounds (SB p.7) Functional Groups

  23. New Way Chemistry for Hong Kong A-Level 3A 21.3 Classification of Organic Compounds (SB p.7) Functional Groups • Propane does not react with sodium • Ethanol and propan-1-ol react with sodium to give hydrogen gas

  24. New Way Chemistry for Hong Kong A-Level 3A and 21.3 Classification of Organic Compounds (SB p.7) Functional Groups • have similar chemical properties •  they contain the same functional group –OH •  they are classified into the same homologous series — alcohols

  25. New Way Chemistry for Hong Kong A-Level 3A CH4 C2H6 C3H8 C4H10 21.3 Classification of Organic Compounds (SB p.12) Homologous Series 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. CH2 CH2 CH2

  26. New Way Chemistry for Hong Kong A-Level 3A 21.3 Classification of Organic Compounds (SB p.12) The first four members of straight-chain alkanes

  27. New Way Chemistry for Hong Kong A-Level 3A 21.3 Classification of Organic Compounds (SB p.12) The first four members of straight-chain alcohols

  28. New Way Chemistry for Hong Kong A-Level 3A 21.3 Classification of Organic Compounds (SB p.13) Homologous Series • Members in the same series can be represented by a general formula. • e.g. alkanes: CnH2n+2 • alkenes: CnH2n • alkynes: CnH2n-2

  29. New Way Chemistry for Hong Kong A-Level 3A 21.3 Classification of Organic Compounds (SB p.13) Homologous Series • Members in the same series can be represented by a general formula. e.g. alkanols: CnH2n+1OH alkanals: CnH2n+1CHO alkanoic acids: CnH2n+1COOH

  30. New Way Chemistry for Hong Kong A-Level 3A Chemical properties 21.3 Classification of Organic Compounds (SB p.13) Homologous Series Functional group of an organic compound Members of a homologous series have similar chemical properties

  31. New Way Chemistry for Hong Kong A-Level 3A 21.3 Classification of Organic Compounds (SB p.13) Homologous Series • The physical properties change gradually along the homologous series • e.g. the longer the carbon chain in the molecule ( or the greater the molecular mass) • the greater the attractive force between molecules •  the higher the melting point, boiling point and density

  32. New Way Chemistry for Hong Kong A-Level 3A 21.3 Classification of Organic Compounds (SB p.13) Some physical properties of the first 20 members of straight-chain alkanes

  33. New Way Chemistry for Hong Kong A-Level 3A 21.3 Classification of Organic Compounds (SB p.13) Some physical properties of the first 20 members of straight-chain alkanes

  34. New Way Chemistry for Hong Kong A-Level 3A Example 21-3A Example 21-3B Check Point 21-3 Example 21-3C 21.3 Classification of Organic Compounds (SB p.13)

  35. New Way Chemistry for Hong Kong A-Level 3A 21.4 Factors Affecting the Physical Properties of Organic Compounds Refer to notes on ‘Bonding and Structure’ pp.77-92 – intermolecular forces

  36. New Way Chemistry for Hong Kong A-Level 3A 21.4 Factors Affecting the Physical Properties of Organic Compounds (SB p.17) Main Factors Affecting the Physical Properties of Organic Compounds 1. Structure of the functional group 1.1 Dipole moment of the molecule 1.2 Formation of hydrogen bonding 2. Length of carbon chains (London dispersion forces)

  37. New Way Chemistry for Hong Kong A-Level 3A 21.4 Factors Affecting the Physical Properties of Organic Compounds (SB p.17) Structure of Functional Group • Molecules having a polar functional group have a higher b.p.than others with a non-polar functional group of similar molecular masses •  Stronger intermolecular attraction among molecules

  38. New Way Chemistry for Hong Kong A-Level 3A 21.4 Factors Affecting the Physical Properties of Organic Compounds (SB p.17) Structure of Functional Group

  39. New Way Chemistry for Hong Kong A-Level 3A 21.4 Factors Affecting the Physical Properties of Organic Compounds (SB p.18) Dipole Moment of Molecule • Tetrachloromethane has 4 polar bonds in the molecule • M.p. and b.p. are very low •  the molecule is non-polar •  the molecule is tetrahedrally symmetrical •  the dipole moments of the C  Cl bond cancel each other

  40. New Way Chemistry for Hong Kong A-Level 3A 21.4 Factors Affecting the Physical Properties of Organic Compounds (SB p.18) Examples of Polar Molecules with Net Dipole Moment

  41. New Way Chemistry for Hong Kong A-Level 3A 21.4 Factors Affecting the Physical Properties of Organic Compounds (SB p.18) Examples of Non-polar Molecules with No Net Dipole Moment

  42. New Way Chemistry for Hong Kong A-Level 3A Let's Think 2 21.4 Factors Affecting the Physical Properties of Organic Compounds (SB p.18) Solubility of Organic Molecules • Depends on the polarity of organic molecules and the solvent • Non-polar or weakly polar compoundsdissolve readily in non-polar or weakly polar solvents • Highly polar compounds dissolve readily in highly polar solvents • “Like dissolves like”

  43. New Way Chemistry for Hong Kong A-Level 3A Hexane in tetrachloromethane Hexane in water 21.4 Factors Affecting the Physical Properties of Organic Compounds (SB p.18) Solubility of Organic Molecules

  44. New Way Chemistry for Hong Kong A-Level 3A Intermolecular forces between hexane and tetrachloromethane molecules Intermolecular forces among hexane molecules and those among tetrachloromethane molecules  21.4 Factors Affecting the Physical Properties of Organic Compounds (SB p.19) Why does Hexane Dissolve Readily in Tetrachloromethane?

  45. New Way Chemistry for Hong Kong A-Level 3A 21.4 Factors Affecting the Physical Properties of Organic Compounds (SB p.19) Why is Hexane Insoluble in Water?

  46. New Way Chemistry for Hong Kong A-Level 3A 21.4 Factors Affecting the Physical Properties of Organic Compounds (SB p.19) Formation of Hydrogen Bonding • Molecules having OH or  NH2 groups are able to form hydrogen bonds • Hydrogen bonds affect the physical properties of alcohols and amines with low molecular masses

  47. New Way Chemistry for Hong Kong A-Level 3A 21.4 Factors Affecting the Physical Properties of Organic Compounds (SB p.20) Why does Propan-1-ol have a Higher Boiling Point?

  48. New Way Chemistry for Hong Kong A-Level 3A 21.4 Factors Affecting the Physical Properties of Organic Compounds (SB p.20) Formation of Hydrogen Bonding • Also affect the solubility of a molecule • Molecules with OH groups are able to form hydrogen bonds with surrounding water molecules •  Soluble in water

  49. New Way Chemistry for Hong Kong A-Level 3A Example 21-4A Let's Think 3 Example 21-4B 21.4 Factors Affecting the Physical Properties of Organic Compounds (SB p.20)

  50. New Way Chemistry for Hong Kong A-Level 3A 21.4 Factors Affecting the Physical Properties of Organic Compounds (SB p.21) Length of Carbon Chains • Molecules with higher molecular masses have higher m.p., b.p. and density •  Higher molecular masses •  Large molecular sizes •  Stronger London dispersion forces among molecules

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