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Describe how you could demonstrate that ethene readily undergoes an addition reaction with bromine water - Leaving Cert Chemistry - Question 10 - 2018
Question 10
Describe how you could demonstrate that ethene readily undergoes an addition reaction with bromine water. Would you expect benzene to readily undergo an addition re... show full transcript
Worked Solution & Example Answer:Describe how you could demonstrate that ethene readily undergoes an addition reaction with bromine water - Leaving Cert Chemistry - Question 10 - 2018
Step 1
Describe how you could demonstrate that ethene readily undergoes an addition reaction with bromine water.
Answer
To demonstrate that ethene undergoes an addition reaction with bromine water, you can follow these steps:
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Setup: Prepare a test tube containing a small amount of ethene by either generating it via dehydration of ethanol or using an ethene gas cylinder.
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Adding Bromine Water: Add a few drops of bromine water (which is initially reddish-brown) to the test tube containing ethene.
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Observation: Gently shake the test tube to mix the ethene and bromine water. You should observe a color change from the reddish-brown color of bromine water to a colorless solution, indicating that bromine has reacted with ethene through an addition reaction.
Step 2
Would you expect benzene to readily undergo an addition reaction with bromine water? Explain your reasoning.
Answer
Benzene is not expected to readily undergo an addition reaction with bromine water due to its stability and structure:
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Stability: Benzene is classified as an aromatic compound, which indicates it has a stable ring structure due to resonance. The electrons are evenly distributed across the ring, providing a level of stability that prevents straightforward addition reactions.
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Bonding Nature: Benzene has no double bonds; rather, it has delocalised electrons occupying a system of overlapping p-orbitals. This delocalisation makes the double bonds 'intermediate' in nature, further resisting addition reactions that would disrupt this stable structure.
Therefore, unless activated by a catalyst, benzene does not react with bromine water under normal conditions.
Step 3
Explain the underlined term.
Answer
The term 'delocalized' refers to electrons in a benzene molecule that are not associated with a specific bond between two atoms. Instead, they are shared among multiple atoms in the molecule. In the case of benzene, these electrons are part of a pi-bonding system that allows them to move freely around the entire hexagonal ring structure formed by the six carbon atoms. This delocalization contributes to the unique stability and reactivity patterns of benzene.
Step 4
Step 5
(ii) involved in sigma bonds between carbon atoms?
Answer
(ii) There are 12 electrons involved in sigma bonds between the carbon atoms. Each carbon atom in benzene forms a single sigma bond with its adjacent carbon, resulting in a total of 6 sigma bonds, with 2 electrons contributing to each bond.
Step 6
What health hazard is associated with benzene?
Answer
Benzene is associated with several health hazards, primarily being carcinogenic. Exposure to benzene can cause cancer, and it is known to be mutagenic, meaning it can damage DNA and alter genetic material. Prolonged exposure can lead to serious health issues such as blood disorders and various types of cancer. Hence, benzene is classified as toxic, harmful, and dangerous.