Muhammed Sabah Comparing Reactivity Of Alkanes and Alkenes Aim: To compare the reactivity of an alkane and an alkene Hypothesis: The cyclohexene would react to the bromine water and turn colourless, whilst the cyclohexane won’t react. Risk Assessment: What’s the problem? | How do you fix? | How does it work? | Bromine water is corrosive to the skin| Wear gloves| Stops the Bromine water from reaching skin| Cyclohexane/ene is highly flammable| Keep away from naked flames. | No naked flame = no ignition. Bromine water is very toxic if inhaled| Conduct experiment in fume cupboard| Gets rid of the fumes so it doesn’t get inhaled. | Equipment: * Dropper bottle of Cyclohexane| * Dropper bottle of Cyclohexene| * Bromine Water| * 4 Test Tubes| * Test tube rack| * Safety Glasses| * Gloves| * 1 pipette| * Fume cupboard| * 2 Dropper bottles labelled A and B, one containing a hexane and one containing a hexene| * Cork Stopper x4| Method: NOTE: * Conduct experiment under dull lighting, as the cyclohexene can react with light. Conduct the experiment inside the fume cupboard, due to the fumes the chemicals give off. 1. Gather all equipment listed, wear safety glasses and gloves, 2. Add 10 drops of Bromine water to a test tube 3. Add 10 drops of cyclohexane to the same test tube 4. Close the test tube with a cork stop, shake gently then place it on the test tube rack 5. Repeat steps 2-4 for cyclohexane then to test tubes “A” and “B” to identify alkene 6. Compare test tubes 3 and 4 with 1 and 2 by checking which test tubes decolourised to determine which one is a hexane and a hexene out of “A” and “B”
Results: Substance| Reaction with Bromine Water| Hydrocarbon (Saturated/unsaturated)| Cyclohexane| Remained yellow| Saturated| Cyclohexene| Yellow Colourless| Unsaturated| A| Yellow Colourless| Unsaturated| B| Remained yellow| Saturated | Reaction of cyclohexene with Bromine water: C6H10(l) + BrOH(aq) C6H10BrOH(l) C6H10 = Cyclohexene BrOH = Bromine Water C6H10BrOH = 2-Bromocyclohexanol Conclusion: When reacted with bromine water alkenes decolourise the liquid whilst alkanes do not react with the Bromine water therefore leaving it yellow.
Discussion: Due to the cyclohexene having double bonds it is easier for the bonds to be broken than the saturated cyclohexane. Some sources of error that could have occurred would be contaminating the chemicals. This is because when the chemicals were added to the test tube they were not dropped from above the test tube as they should have been. Another source of error is not giving the cyclohexane enough time to react with the bromine water. Some improvements that could be done to this experiment is to make sure that when adding the chemicals to the test tube to add them from above the test tube.
Another improvement would be to wait around 5 minutes so that the cyclohexane has time to react. The experiment we conducted is accurate since we have used the best equipment available, although it is not reliable as we have not repeated the experiment at all which could also count as a source of error. The experiment is valid due to the dependent variables being kept constant (Amount of chemicals being used, under same room conditions), it is also valid because the experiment tests the aim.