An Introduction to Organic Chemistry

1. An Introduction to Organic Chemistry By Ng Yisi

2. What is organic chemistry? • The study of carbon-containing compounds • General properties are different from inorganic compounds (e.g., ionic salts, etc.)

3. Organic Compounds • More than 5,000,000 known organic compounds compared to only about 200,000 to 300,000 known inorganic compounds • General properties are different from inorganic compounds (ionic salts etc.)

4. Organic compounds Covalent bonding Low melting points Mainly insoluble in water Mainly soluble in organic solvents (e.g., gasoline) Almost all burn Slower reactions Inorganic compounds • Ionic bonding • High melting points • Mainly soluble in water • Mainly insoluble in organic solvents • Very few burn • Very fast reactions

5. Covalent bonding • A covalent bond involves sharing of a pair of electrons between two atoms • Each atom contributes one electron for sharing • The shared electrons are localised between the two atomic nuclei

6. Covalent bonding • Example H● + H× H H H H can be represented as H—H ● × ● ×

7. Why carbon? • A carbon atom forms four bonds • Carbon atoms form stable bonds with other carbon atoms (i.e., the C—C covalent bond is strong) • Can form chains and even networks • Examples: graphite and diamond

8. Why carbon? • Diamond • Graphite • A carbon atom forms four bonds

9. Why carbon? • Carbon atoms also form stable bonds with other atoms (i.e., C—H, C—O, C—N, C—Cl etc. bonds are strong) • Many combinations and arrangements are possible

10. Examples of Organic Compounds

11. Hydrocarbons (CnHm) • Extracted from crude oil • Separated according to size for various purposes • Source of energy, plastics, solvents, raw materials, etc.

13. Sucrose C12H22O11

14. Ethanol C2H5OH

15. Aspirin (acetylsalicylic acid)

16. Chlorofluorocarbons(CFCs) CFCl3

17. What are organic molecules? • Main structure: carbon backbone • Each carbon must have 4 covalent bonds (i.e., share an electron with a neighbouring atom) • Modular system, building blocks attached to each other by covalent bonds • Functional groups with specific properties

18. Examples of functional groups • Alkene C=C • Alcohol –OH • Halogen groups –Cl, –Br • Amine –NH2 • Carboxylic acid –COOH • Amide –CONH • etc.

19. Esters

20. Esters Synthesised when a carboxylic acid and an alcohol react

21. Esters • Responsible for many flavours and fragrances • Generally sweet and pleasant smells

22. Structure Flavour Banana Orange Pineapple Apple Raspberry Esters

23. Esters: Other applications • Aspirin, an analgesic (painkiller) • Ethyl acetate, a solvent • Polyesters

24. Polyesters: applications • Clothing (e.g., Dacron, terylene) • In sheet-form: tape • Used to make synthetic arteries for heart surgery • Absorbable staples for surgery