Describe how you would carry out a lab test to compare the reactivity of liquid 1-heptene and liquid heptane. State clearly what the possible results of the test are and what they would indicate.

  1. Would you carry out the lab test using bromine? Add about 1 mL (about twenty drops) of 1-heptene to one container and about 1 mL of heptane to the other container.

  2. Add an equal volume of bromine water to each of the liquids then shake each container to the same extent.

  3. Leave the containers to settle, then observe.

Would this process work for heptane and 1-heptene? Would the colour of the solution change?


According to this Wikipedia article:

"In electrophilic halogenation the addition of elemental bromine or chlorine to alkenes yields vicinal dibromo- and dichloroalkanes (1,2-dihalides or ethylene dihalides), respectively. The decoloration of a solution of bromine in water is an analytical test for the presence of alkenes."

Alkanes tend to be much less reactive toward bromine, so yes, your bromine water test should allow you to distinguish between heptane and 1-heptene.


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