Describe two chemical tests that can be used to distinguish between the following pair of compounds?

PLEASE, WRITE OUT THE EQUATIONS, INCLUDING THE REAGENTS AND THE PRODUCTS.
i) butane and 2-butene

1 Answer
Oct 9, 2017

Answer:

Try the bromine decolourization test and the Baeyer unsaturation tests.

Explanation:

Test 1. Bromine decolourization test

Add a few drops of a solution of #"Br"_2# in #"CCl"_4# to a solution of each hydrocarbon in #"CCl"_4#.

The butane will not react (left-hand test tube). The but-2-ene will decolourize the bromine solution (right-hand test tube).

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#"CH"_3"CH=CHCH"_3 + underbrace("Br"_2)_color(red)("brown") → underbrace("CH"_3"CHBrCHBrCH"_3)_color(red)("colourless")#

Test 2. The Baeyer test

Bubble each gas through a cold, dilute, aqueous solution of #"KMnO"_4#.

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With butane, there will be no colour change (top test tube).

With but-2-ene, the purple colour will disappear and a dark brown precipitate will form (bottom test tube).

#"3CH"_3"CH=CHCH"_3 + underbrace("2MnO"_4^"-")_color(red)("purple") + 4"H"_2"O"#

#→ "3CH"_3"CH(OH)CH(OH)CH"_3 + underbrace("2MnO"_2)_color(red)("dark brown precipitate") + 2"OH"^"-"#