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Cyclohexene (boiling point = 83 °C) can be prepared by the dehydration of cyclohexanol (boiling point = 161 °C) using concentrated phosphoric acid - AQA - A-Level Chemistry - Question 3 - 2018 - Paper 3
Question 3
Cyclohexene (boiling point = 83 °C) can be prepared by the dehydration of cyclohexanol (boiling point = 161 °C) using concentrated phosphoric acid. A student prepar... show full transcript
Worked Solution & Example Answer:Cyclohexene (boiling point = 83 °C) can be prepared by the dehydration of cyclohexanol (boiling point = 161 °C) using concentrated phosphoric acid - AQA - A-Level Chemistry - Question 3 - 2018 - Paper 3
Step 1
Step 2
Describe a test-tube reaction, on the product, to show that the cyclohexanol had been dehydrated.
Answer
To indicate that cyclohexanol has been dehydrated, you can add bromine solution to the cyclohexene. The addition of bromine, which is brown in color, will lead to a decolorization of the solution, confirming that a double bond has formed.
Step 3
Step 4
Step 5
Give a property of anhydrous calcium chloride, other than its ability to absorb water, that makes it suitable as a drying agent in this preparation.
Answer
Anhydrous calcium chloride is hygroscopic, which means it has a strong affinity for water vapor in the atmosphere, allowing it to effectively remove moisture from the organic layer.
Step 6
Describe the apparatus used to remove the drying agent by filtration under reduced pressure.
Answer
The apparatus consists of a round-bottomed flask connected to a vacuum pump, a Buchner funnel with filter paper placed on top, and a side arm flask. The mixture containing the drying agent is poured into the Buchner funnel, where the vacuum draws the liquid through the filter paper, leaving the drying agent behind.
Step 7
Step 8
Explain how an infrared spectrum would confirm that the cyclohexene obtained from the chromatography did not contain any cyclohexanol.
Answer
In the infrared spectrum, cyclohexene will show no O-H stretching absorption peaks, which are characteristic of alcohols like cyclohexanol. Therefore, the absence of such peaks would confirm that the product does not contain cyclohexanol.