SK025 Exp 4 Reactions of Aliphatic and Aromatic Hydrocarbons

Summary

The video demonstrates a chemical experiment involving reactions with bromine in dichloromethane and oxidation with potassium permanganate (Bayer's test). The first part focuses on adding bromine to various compounds (cyclohexane, cyclohexene, and toluene) in different test tubes, observing the changes under sunlight and darkness. The second part shows the oxidation of these compounds using an alkaline potassium permanganate solution, followed by recording observations. The experiment's goal is to observe the different reactions and tabulate the results for analysis.

Takeaways

• 😀 The experiment involves reactions with bromine in dichloromethane and oxidation with potassium permanganate solution.
• 😀 Dry and clean test tubes (labeled A2F) are needed for the experiment.
• 😀 Cyclohexane, cyclohexene, and toluene are used in different test tubes (A, B, C, D, E, and F).
• 😀 A few drops of 4% bromine in dichloromethane are added to each test tube, followed by shaking.
• 😀 Test tubes A, C, and E should be kept in a dark place, while B, D, and F are exposed to sunlight.
• 😀 The reaction should be observed after 15 minutes, depending on weather conditions.
• 😀 Black sugar paper is used to wrap test tubes A, C, and E to block light.
• 😀 Part B of the experiment involves oxidation with alkaline potassium permanganate solution, known as Bayer's test.
• 😀 Test tubes G, H, and I are labeled for cyclohexane, cyclohexene, and toluene, respectively.
• 😀 Three drops of alkaline potassium permanganate solution are added to each test tube (G, H, I), followed by shaking.
• 😀 Observations from both parts A and B are recorded and tabulated for analysis.

Q & A

What is the purpose of wrapping test tubes A, C, and E with black sugar paper?

Wrapping test tubes A, C, and E with black sugar paper is meant to block out light, ensuring that the reactions in these test tubes occur in the dark. This is typically done to observe the effects of light-sensitive reactions or to control the conditions of the experiment.

Why is cyclohexane used in this experiment?

Cyclohexane is used in the experiment to serve as a control or comparison for the reactivity of other substances. Its non-reactive nature in this context helps to highlight how bromine reacts with other compounds like cyclohexene and toluene.

What role does bromine in dichloromethane play in this experiment?

Bromine in dichloromethane is used as a reagent to test the reactivity of various compounds. The experiment investigates how bromine reacts with different substances like cyclohexane, cyclohexene, and toluene, particularly observing the color change as an indicator of reaction.

Why are test tubes B, D, and F placed under sunlight?

Test tubes B, D, and F are placed under sunlight to expose them to light and investigate the impact of light on the reaction. This allows comparison with the reactions in the dark (test tubes A, C, and E), helping to analyze how light influences the bromine reaction.

What is the expected outcome after shaking the test tubes with bromine solution?

After shaking the test tubes with bromine solution, a color change is expected. For example, a reaction typically leads to the decolorization of bromine, indicating that a reaction has occurred with compounds such as cyclohexene, but not with non-reactive compounds like cyclohexane.

What is the purpose of the Bayer's test in Part B?

The Bayer's test is used to detect the presence of alkenes. In this experiment, alkaline potassium permanganate solution is added to test tubes containing cyclohexane, cyclohexene, and toluene to observe whether a reaction occurs, which would indicate the presence of an alkene group.

What is the significance of the observations in both parts of the experiment?

The observations help to determine the reactivity of the substances involved. In Part A, the color change in response to bromine indicates the presence of double bonds in compounds like cyclohexene. In Part B, the reaction with potassium permanganate confirms the presence of alkenes by the characteristic color change.

What does the reaction between potassium permanganate and cyclohexene indicate?

The reaction between potassium permanganate and cyclohexene indicates that cyclohexene contains a double bond, as the permanganate solution is decolorized in the presence of alkenes, showing that oxidation has occurred.

Why is it important to tabulate the observations from both parts of the experiment?

Tabulating the observations is important to systematically record the results and make comparisons between the reactions of cyclohexane, cyclohexene, and toluene with bromine and potassium permanganate. This structured data allows for clear analysis and conclusions to be drawn.

How long should the test tubes be left in sunlight, and why does this depend on the weather?

The test tubes should be left in sunlight for about 15 minutes, although the exact time depends on the weather conditions. The intensity of sunlight varies, so the reaction time may need to be adjusted accordingly to observe any changes in the test tubes.