Reactivity of alkanes and alkenes practical notes PDF

Preview

Summary

Reactivity of alkanes and alkenes practical notes...

Description

Reactivity of alkanes and alkenes Practical Notes Aim: To compare the reactivity of cyclohexane and cyclohexene using bromine water

Risk Assessment: Hazard (1): Prevention (1): Risk Management (1):

Chemical burn/damage to eyes Wear safety glasses Use eye washing station immediately. Seek medical assistance if required. Breathing vapours of bromine water Place bromine water in a fume cupboard Seek medical attention immediately

Hazard (2): Prevention (2): Risk Management (2):

Materials and Method: Reference: Thickett, G. (2006). Chemistry2 (p. 27). Milton, Qld.: Jacaranda. In-text citation: Page 27

Results Table: Observations Combinations: Bromine Water

Hexane Coloured orange/brown colour -> separated into 2 layers. Dark orange on top and pale orange on the bottom

Hexene Coloured orange/brown colour -> separated into 2 layers. Cloudy white on top and clear colourless on the bottom

Analysis: 1. Identify the functional group that reacts with the bromine water. Alkenes reacts with the bromine water. 2. Bromine water is a mixture of bromine and water molecules as well as hydrogen ions, bromide ions and hypobromous acid (HOBr), which have formed as some bromine molecules react with the water solvent. Write a balanced symbolic equation for this equilibrium reaction. H2O + Br2 -> Br- + H+ + HOBr

3. When the bromine water decolourises as it reacts with the alkene, the reaction involves the addition of HOBr molecules across the double bond of the cyclohexene to form an alkanol. In the reaction performed in the experiment above, the product is called 2bromocyclohexanol (C6H12BrOH). Write a balanced equation for the reaction of HOBr with cyclohexene. C6H10 + HOBr--> C6H10BrOH 4. Use your experimental observations with bromine water and cyclohexane to explain whether bromine molecules are more soluble in water or in cyclohexane From the experiment, bromine water is more soluble in water as the bromine water did not dissolve much in the cyclohexane. 5. Identify the variables that need to be controlled in this experiment Concentration and volume of bromine water and cyclohexane, temperature, 6. Discuss the validity of this technique in distinguishing alkanes from alkenes This technique to distinguish alkanes and alkenes is very good, however it does not tell you which species of alkenes and alkanes you have.

Conclusion: The reactivity of alkenes with bromine water is higher than the reactivity of alkanes with bromine water as alkanes are saturated while alkenes are not.

Dark orange on top of pale orange.top layer is hexane. Bromine is more soluble in hexane (also nonpolar) than in in water - hexane CLOUDY white on clear colourless, Hex-1ene, bromine added across the double bond in hexane Compare because 1. Liquid at room temp, 2. Less volatile...