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  1. Introduction to Organic Chemistry (What are Things Made of?) IJSO Training (Phase 2) Dr. Kendrew K. W. Mak Department of Chemistry The Chinese University of Hong Kong

  2. Roles of Organic Chemistry in Daily Life Organic compounds (有機化合物) can be found in: and a lot more ……

  3. What is Organic Chemistry (有機化學) Classical Definition Compounds obtained or derived from living organisms Modern Definition Compounds that are made up of carbon atoms. About 13 million organic compounds are known today. About 100,000 new ones discovered every year. There are only 200,000 to 300,000 known inorganic compounds (those are made up of elements other than carbon)

  4. Interesting Organic Compounds – Compounds having favorable aromas Vanillin (香草醛) Tetramethylpyrazine(川芎嗪)

  5. Organic Compounds Natural Organic Compounds Proteins (蛋白質), enzyme (酵), vitamins (維生素), lipids (脂質) , carbohydrates (碳水化合物), nucleic acid (核酸) …… Synthetic (Man-made Compounds) Synthetic fabrics (合成織品), plastics (塑膠), synthetic rubber (合成橡膠), medicine (藥物) , adhesives (黏合劑), photographic film (攝影菲林) ……

  6. Diversified Structures Complex Simple

  7. Hydrocarbons – Contain only Carbon and Hydrogen Atoms Organic compounds that contain only carbon and hydrogen are called hydrocarbons (碳氫化合物). Hydrocarbons differ from one another in the number of carbon atoms present in one molecule, and the ways that they are bonded together. Methane (甲烷) has one carbon atom, and octane (辛烷) has eight. Polyethylene (聚乙烯) contains hundreds to thousands of carbon and hydrogen atoms in each molecules. Methane (CH4) Octane (C8H18) Polyethene

  8. Molecular Sizes and Properties Physical Properties of Some Alkanes (烷烴)

  9. Structural Isomers of Hydrocarbons Hydrocarbons also differ from one another in the way the carbon atoms bonded to each other. n-Pentane, C5H12 iso-Pentane, C5H12 neo-Pentane, C5H12 Straight chain (直鏈) Branched chains (支鏈)

  10. iso-Pentane, C5H12 neo-Pentane, C5H12 n-Pentane, C5H12 Structural Isomers of Hydrocarbons Boiling Point. The number of possible structural isomers (異構體) of a chemical formula increases rapidly as the number of carbon atoms increases. 36°C 30°C C5H12 3 isomers C8H18 75 isomers C20H42 366,316 isomers 10°C

  11. Conformers – Same Molecule with Different Spatial Orientations

  12. Petroleum (石油) – Major Source of Hydrocarbon Petroleum (also known as crude oil) is a complex mixture consisting mainly of alkanes. It corresponds to the fossil (化石) remains of microscopic animals that lived in the seas in ancient times. Fractional distillation (分餾)

  13. Alkane – The Simplest Form of Hydrocarbon Methane (CH4) Natural Gas Biogas (marsh gas) Butane (丁烷) (C4H10) Liquefied petroleum gas (液化石油氣)(LPG) Lighter gas

  14. Alkane – The Simplest Form of Hydrocarbon Octane Number (辛烷值) 0 Heptane 100 2,2,4-Trimethylpentane

  15. Boosting Up the Octane Number Anti-Knocking Agent (抗震劑) Tetramethyl lead (四甲基鉛), Pb(CH3)4 Tetraethyl lead (四乙基鉛), Pb(C2H5)4 Cause air pollution - Produce smog (煙霧) Toxic – leukemia (白血病)

  16. Saturated and Unsaturated Hydrocarbons Saturated Hydrocarbons – contain single bonds only Unsaturated Hydrocarbons – contain multiple bonds Saturated hydrocarbon(飽和碳氫化合物) Unsaturated hydrocarbon (不飽和碳氫化合物) n-Butane, C4H10 But-2-ene, C4H8 (丁烷) (丁-2-烯)

  17. Alkenes – Hydrocarbons with C=C Double Bonds Ethene/Ethylene (乙烯) (C2H4) – The simplest alkene (烯) Use: Making polymer (polythene) A plant hormone (triggers fruit ripening) (胡蘿蔔素) Beta-carotene is the precursor molecule to vitamin A

  18. Alkenes – Hydrocarbons with C=C Double Bonds Polymerization (聚合作用)

  19. 121.7° H H 1.08Å 116.6° C C 1.33Å H H A double bond consists of one σ bond and one p bond Sigma (s) Bond and Pi (p) Bond Compounds with double covalent bond Ethene (CH2=CH2) Pi (p) – side-to-side overlap Double covalent bond = 1 s bond + 1 p bond

  20. Geometrical Isomers (幾何異構體)of Alkene (順-丁-2-烯) (反-丁-2-烯)

  21. C=C Double Bonds:Absorption of Light UV-C: below 280 nm UV-B: 280 nm – 320 nm UV-A: 320 nm – 400 nm Visible light: 400 nm – 700 nm 1 nm = 10-9 m

  22. Sunscreens (防曬霜) not very soluble in oily skin lotions

  23. C=C Double Bonds:Absorption of Light -carotene (胡蘿蔔素)max = 455nm carrots, apricots, sweet potatoes (orange) lycopene(番茄紅素)max = 474nm tomatoes, watermelon, pink grapefruit(red) 1 nm = 10-9 m

  24. Benzene and Aromatic Compounds The electrons of the double bonds in benzene (苯) are not confined between any two carbon atoms. These electrons are able to move freely around the ring. some common aromatic compounds (芳香族化合物): Toluene Naphthalene 1,4-Dichlorobenzene

  25. The Delocalization of Electrons in Benzene I II Resonance structures (共振結構) of benzene

  26. “cyclohexatriene” + 3H2 36 kcal/mol (151kJ/mol) Potential energy benzene + 3H2 H° = -85.8 kcal/mol (-359kJ/mol) H° = -49.8 kcal/mol (-208kJ/mol) cyclohexane The Delocalization of Electrons in Benzene • A compound with delocalized electrons is more stable than it would be if all of its electrons were localized. • The extra stability a compound gains from having delocalized electrons is called delocalization energy (離域能) or resonance energy (共振能) .

  27. Delocalization (離域作用) – Two More Examples Delocalization in the carbonate ion Bonding in ethanoic acid and the ethanoate ion

  28. Organic Molecules are Classified by Functional Groups Boiling point = - 88°C A gas at room temperature Insoluble in water. Ethane(C2H6) Boiling point = + 78°C A liquid at room temperature Soluble in water For making alcoholic beverages Ethanol(C2H5OH) A corrosive (腐蝕性), pungent (刺激性), highly toxic gas Ethylamine(C2H5NH2)

  29. Organic Molecules are Classified by Functional Groups Function group (官能基) is defined as a combination of atoms that behave as a unit.

  30. Alcohols Contain the Hydroxyl Group Alcohols are organic molecules in which a hydroxyl group is bonded to a saturated carbon. Methanol(甲醇) Isopropanol (異丙醇) • Making methylated spirit • Fuel for racing car • Rubbing alcohol

  31. Alcohols Contain the Hydroxyl Group Ethanol Fermentation (發酵作用)

  32. Transformation of Function Groups Conversion of alkenes to alcohols (hydration水合作用) An acid-catalyzed reaction

  33. Interconversion of Alcohols and Alkyl Halides bromomethane

  34. Some Common Halogenated Hydrocarbons Some Halogenated Hydrocarbons

  35. Reactions of Alcohols and Halogenated Hydrocarbons Diethyl ether Diethyl ether was used as an anesthetic (麻醉劑) starting from mid-19th century. A commonly used laboratory solvent. • It burns very completely and reduces the emission of carbon monoxide. • Very high octane rating (116), replace aromatic hydrocarbons • Very strong odor, sickening to some people. • Decompose very slowly in nature, polluting the environment. MTBE as fuel additive (燃料添加劑) Methyl tert-butyl ether (MTBE)

  36. Stereoisomers (立體異構體) (Different shapes) Structural Isomers(結構異構體) (Different bonding) Positional Isomers 位置異構體 Hydrocarbon Chain Isomers 碳氫鏈異構體 Functional Group Isomers 官能基異構體 Geometric Isomers 幾何異構體 Enantiomers (Optical Isomers) 對映異構體(旋光異構體) Different Types of Isomers Isomers

  37. Different Types of Isomers Positional Isomers Hydrocarbon Chain Isomers Functional Group Isomers

  38. Different Types of Isomers Geometric Isomers Enantiomers (Optical Isomers) (See next page……)

  39. Optical Isomers and Chiral Compounds Asymmetric Carbon (不對稱碳原子) – is a carbon atom that bonded to four different groups An asymmetric carbon can be known as a chiral (手性) center

  40. Conversion of Alcohols to Aldehydes (醛) Very toxic The aldehydegroup Less toxic Oxidation Reaction (氧化反應)

  41. Some Common Aldehydes • Large amounts of formaldehyde are used for producing adhesives for making plywood (夾板). • Embalming (防腐) Formaldehyde(甲醛)

  42. Some Common Aldehydes

  43. From Wine to Vinegar White vinegar – 5% acetic acid solution Carboxyl group

  44. Tartaric acid Malic acid Lactic acid Carboxylic Acids Found in Foods AHAs Alpha-hydroxy acids AHAs contain a hydroxyl group (-OH) bonded to the first carbon atom attached to the –COOH group. Citric acid

  45. Reactions of Carboxylic Acids with Alcohols ester linkage (酯鍵合)

  46. Some Esters (酯) and Their Odors

  47. More About Oxidation and Reduction Reactions • Oxidation (in organic chemistry) – often refers to: • gaining oxygen atoms (+ O) • losing hydrogen atoms (- H) oxidation –氧化作用; reduction –還原作用

  48. More About Oxidation and Reduction Reactions • Reduction (in organic chemistry) – often refers to: • losing oxygen atoms (- O) • gaining hydrogen atoms (+ H)

  49. More About Oxidation and Reduction Reactions

  50. Amines (胺) and Amides (酰胺) Amines – substances with “fishy” smell. Amides – linking the amino acids in proteins