EXPERIMENT #5 Experiment 4: Reactions of Aliphatic and Aromatic Hydrocarbons. TST0925 Physical & Organic Chemistry LINK: https://www.youtube.com/watch?v=Hnhialttk2k Materials: cyclohexane cyclohexene potassium permanganate (KMnO4) toluene evaporating dish match bond paper dropper matchstick PROCEDURE: Method A: Combustion Test 1. 2. 3. 4. 5. Place a few drops of cyclohexane in an evaporating dish. Ignite a match stick and place it in the cyclohexane-containing evaporating dish. Hold a piece of bond paper and place it above the flame. Observe. Place a few drops of cyclohexene in another evaporating dish. Do the same steps 2-4 for cyclohexene. Observe. Method B: Oxidation Test with Basic, Cold KMnO4 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. Prepare a clean and dry test tubes, preferably three. Apply 2 ml of cyclohexane on one of the test tubes. Add 10 drops of basic KMnO4 to the test tube containing cyclohexane. Shake the test tube. Observe and record the initial color of the liquid. Get a test tube and put 2 ml of cyclohexene in it. Add 10 drops basic KMnO4 to the test tube containing cyclohexene. Shake the test tube. Observe and record the initial color of the cyclohexene and KMnO 4. Lastly, add 2 ml of toluene on the remaining test tubes. Add 10 drops of basic KMnO4 to the test tube containing toluene. Shake the test tube and observe. RESULTS In doing the first method of the experiment which is the combustion test, we observed that cyclohexane produced blue flame and soot, which was determined by exposing a bond paper above the flame produced by igniting a cyclohexane with a matchstick. But we also observed that cyclohexene produced a bigger flame with more blue color intensity than cyclohexane, which produced more soot. In doing the oxidation test with potassium permanganate, we observed that the color of KMnO 4 remained when mixed with cyclohexane. While in the case of cyclohexene, the deep purple color of KMnO 4 decolorized and brown precipitate is formed. But in toluene, the deep purple color of KMnO 4 only decolorized and no precipitate is produced. In conclusion, cyclohexane is less reactive and relatively than cyclohexenes which are comparatively reactive and relatively unstable due to its double bond. EXPERIMENT #6 CHEMY102 Experiment 8B Alkane/Alkene LINK: https://www.youtube.com/watch?v=pV9sJaxiP_Q&t=169s MATERIALS: test tubes cyclohexane cyclohexene yellow bromine water potassium permanganate dropper PROCEDURE: A. Using yellow bromine water 1. 2. 3. 4. Label four test tubes, two for cyclohexane and two for cyclohexene. Add 1 ml of cyclohexane to one of the test tubes. Add 1 ml of cyclohexene to one of the test tubes. Add a small amount of yellow bromine water to test tubes containing cyclohexane and cyclohexene. 5. Shake and let it settle. Observe. B. Using KMnO4 1. 6. 7. 2. 3. Use second set of test tubes. Add 1 ml of cyclohexane to one of the test tubes. Add 1 ml of cyclohexene to one of the test tubes. Add a small amount of potassium permanganate to each of the test tubes. Shake and let it settle. Observe. RESULTS When the cyclohexane was mixed with yellow bromine water, we observed that the reaction was slightly slow and no changes in color or decolorization observed as the color of the bromine water remained the same. While cyclohexene reacted quickly after the shaking of test tube and the bromine water decolorized, resulting to transparent color of mixture. The reactions of two hydrocarbons to KMnO 4 are also the same. The color of KMnO4 remained the same when the shaking of test tube with KMnO 4 occurred, and there were also two layers of liquid as the compounds did not mix. While cyclohexene decolorized the potassium permanganate from purple to brown. EXPERIMENT #17 Cracking a hydrocarbon LINK: https://www.youtube.com/watch?v=ZYyKUePdC2Y MATERIALS: Bunsen burner delivery tube bung boiling tube mineral wool pumice stones liquid paraffin clamp water test tubes and bungs test-tube rack pipette bromine water potassium permanganate lighter PROCEDURE: 1. Put a mineral wool into the bottom of boiling tube. 2. Soak the mineral wool with 2 cm 3 of liquid paraffin using pipette. Make sure to soak the liquid paraffin to the mineral wool completely and there should be no excess. 3. Clamp the boiling tube horizontally and place the clamp near the mouth of the tube. 4. Put some pumice stones into the boiling tube. 5. Tilt the tube to spread the pumice stones. 6. Attach a bong with a delivery tube to the mouth of boiling tube. 7. Prepare a bowl of water with six test tubes that are filled with water and enclosed by bung. 8. Heat the pumice stones using the hottest part of the flame just beyond the blue cone of Bunsen flame. 9. Call and ask an assistant to collect the gas into the test tubes coming from the heated boiling tube through delivery tube. 10. After heating the pumice stones, briefly heat the liquid paraffin soaked in the mineral wool, preferably about 1 second, then heat the pumice stones again. Repeat this step to keep the boiling tube hot and to avoid suck back. 11. Continue until the six test tubes have been filled with gas. 12. Observe if there is still water in the tube. Make sure that there is no water remaining. 13. Test the test tubes three to six as the first two test tubes will mostly contain air. A. Test tube 3 by smelling the gas. B. Test tube 4 by igniting the gas with lighter. C. Test tube 5 by adding few drops of bromine water D. Test tube 6 by adding few drops of KMnO4. RESULTS: Cracking hydrocarbon is a process that converts long chain alkanes into smaller alkane and alkene molecule. In this experiment, we used the liquid paraffin to serve as the alkane to be broken down into smaller chains by heating and using catalyst which is the pumice stones. By testing the gas collected, we have observed the presence of carbon-carbon double bond or simply, alkenes. The test tube 3 smelt of camping gas, which is a mixture of butane and propane. When we ignited the gas collected from test tube 4, we have observed that the gas is flammable. When we added a few drops of bromine water into the gas collected in test tube 5, we saw that the bromine water went colorless. The decolorization of bromine is a simple and effective chemical test for an alkene, therefore the gas in the test tube is truly an alkene. And lastly, we have observed that the potassium permanganate also went colorless when we mixed it with the gas in the test tube 6. Just like the situation occurred in test tube 5, we can conclude that there is presence of alkene in the gas. Post Lab #6 Aromatic compounds are stable and not very reactive because of their aromaticity which is the property of organic compounds that have at least one conjugated ring of alternate single and double bonds, exhibiting extreme stability. Aromatic compounds also have aromatic rings that must contain only sp2hybridized atoms that can form a delocalized system of π molecular orbitals. Their delocalization of pielectrons makes them stable and less vulnerable to reaction.
