# 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

Oct 9, 2017

Try the bromine decolourization test and the Baeyer unsaturation tests.

#### Explanation:

Test 1. Bromine decolourization test

Add a few drops of a solution of ${\text{Br}}_{2}$ in ${\text{CCl}}_{4}$ to a solution of each hydrocarbon in ${\text{CCl}}_{4}$.

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

"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 ${\text{KMnO}}_{4}$.

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).

$\text{3CH"_3"CH=CHCH"_3 + underbrace("2MnO"_4^"-")_color(red)("purple") + 4"H"_2"O}$

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