An Introduction to Organic Chemistry

1. An Introduction to Organic Chemistry

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

3. Comparison

4. 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 • Example H● + H×  H ●× H H ●× H can be represented as H—H

5. 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 • 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

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

7. Sucrose C12H22O11

8. Ethanol C2H5OH

9. Aspirin (acetylsalicylic acid)

10. Chlorofluorocarbons(CFCs) CFCl3

11. 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

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

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

14. Esters • Responsible for many flavours and fragrances • E.g.  banana flavour • Generally sweet and pleasant smells • Aspirin, an analgesic (painkiller) • Ethyl acetate, a solvent • Polyesters

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

16. Racing Raisins

17. Apparatus/Chemicals • one package of raisins • a large beaker (800ml) • carbonated water • stop clock

18. Procedure • Choose a raisin to drop into a large beaker of carbonated water • Time how quickly the raisin sinks and rises back to the surface • Race with each other! • Observe the bubbles forming on the food surface during the experiment

19. Science behind • A raisin is denser than water  it will initially sink • Carbonated water contains carbon dioxide bubbles • Rough surface creates a large surface area for the bubbles to attach to • As the number of bubbles increases on the raisin, raisin and bubbles become less dense than water, hence rising to the surface

20. Science behind • Once it has risen to the surface, the bubbles burst, releasing the carbon dioxide into the air • Hence raisin sinks again • Therefore, the items that work best will have a density that is only slightly greater than that of water

21. SMOKE BOMB

22. Apparatus • Hotplate • Satay Stick • Aluminum foil • Lighter • Mould • Wick • Lighter

23. Chemicals • Potassium nitrate • Sugar (sucrose or table sugar) • Chemicals Used to Color Flames • Red - strontium salts • Orange - calcium chloride Yellow - sodium nitrate • Green - barium salts, such as barium nitrate

24. Procedure • Add sugar to potassium nitrate in the ratio of 2:3 on a piece of aluminum foil. • Add chemical that colour the flame, sparingly. • Heat the mixture on a hotplate on low heat. • Stir the mixture well using a satay stick. • When the mixture turned brown, take it off the heat and wrap the mixture with that aluminum foil. • When it has hardened – takes about 10minutes – light it up and coloured flames will be produced.

25. Chemistry Behind • Sugar – fuel • Potassium nitrate- oxidizer • Salt- organic dye • 48NaNO3 + 5C12H22O11- 60CO2 + 55H2O + 24N2 + 24Na2O

26. Red cabbage indicator • A simple test to determine the pH of household solution – acidic or basic?

27. Apparatus/Chemicals • red cabbage • blender or knife • filter paper • one large glass beaker • glass rod • Heater • lemon juice • vinegar • milk • seven up • coffee • baking soda • household bleach • masonry's cleaner

28. Procedure • Chop the cabbage into small pieces. • Place the cabbage in a large beaker and add water to cover the cabbage. Allow at least ten minutes for the color to leach out of the cabbage. • Filter out the plant material to obtain a red-purple-bluish colored liquid. This liquid is at about pH 7. • Soak a filter paper in this liquid. Allow it to dry. Cut the dry colored paper into test strips. • Use a dropper or toothpick to apply a little liquid to a test strip. • Compare the colour change

30. Chemistry behind • Red cabbage contains a pigment molecule called flavin (an anthocyanin) • This water-soluble pigment is also found in apple skin, plums, poppies, cornflowers, and grapes. acidic neutral basic -

31. - The color of the juice changes in response to changes in its hydrogen ion concentration. • - Acids will donate hydrogen ions in an aqueous solution and have a low pH (pH < 7). • - Bases accept hydrogen ions and have a high pH (pH > 7).

32. What is pH? • A solution whose pH is 7 is said to be neutral, that is, it is neither acidic nor basic. Water is subject to a self-ionisation process. • H2O H+ + OH− • pH indicators are frequently employed in titrations in analytic chemistry and biology experiments to determine the extent of a chemical reaction. • Common pH indicators in lab: • Phenolphthalein • methyl orange • methyl green

33. Cornflour Slime

34. Apparatus/Chemicals • A big beaker • Cornflour • Water

35. Procedure • Put the cornflour in the bowl and while stirring, add water a little at a time until all the cornflour is wet. • Keep adding water, a little by little, and stirring until a thick slime forms. Be careful not to add too much water. • Make a fist and punch the surface of the slime - the slime will feel hard. • Do the same thing, but very slowly and your hand will emerge from the bowl covered in wet, sloppy slime.

36. Science behind • Cornflour slime is a stir thickening (dilatant) fluid. • Most fluids are ‘Newtonian’ and their viscosity (runniness) stays the same, whether or not they are being stirred. • Cornflour slime is a non-Newtonian fluid. It becomes thicker (more viscous) when stirred (a shear force is applied; punching it works as well). • The slime returns to its runnier (less viscous) state when the force is removed.