Question

Which one of alkane, alkene, and alkyne will not decolorize the bromine solution.

Answer 1

• The organic compounds having a double and triple bond present between two Carbon-Carbon atoms are called alkenes and alkynes respectively.

The unsaturated alkenes and alkynes have the general formula $\left({\mathrm{C}}_{\mathrm{n}}{\mathrm{H}}_{2\mathrm{n}}\right)$ and $\left({\mathrm{C}}_{\mathrm{n}}{\mathrm{H}}_{2\mathrm{n}-2}\right)$.

The organic compounds having a single bond between two Carbon-Carbon atoms are called alkanes.

The saturated alkanes have the general formula is $\left({\mathrm{C}}_{\mathrm{n}}{\mathrm{H}}_{2\mathrm{n}+2}\right)$.

• Ethane $\left({\mathrm{C}}_2{\mathrm{H}}_6\right)$ does not react with a Bromine Water solution because Ethane contains only a single bond between two Carbon atoms.

Ethene $\left({\mathrm{C}}_2{\mathrm{H}}_4\right)$ changes the color of the solution from reddish-orange color to a colorless solution with the addition of Bromine solution.

The chemical equation of the reaction of Ethene with Bromine water is written as:

$$\begin{gathered} {\mathrm{H}}_2\mathrm{C}={\mathrm{CH}}_2\left(\mathrm{g}\right)+{\mathrm{Br}}_2\left(\mathrm{aq}\right)\to {\mathrm{BrCH}}_2-{\mathrm{CH}}_2\mathrm{Br}\left(\mathrm{aq}\right) \\ \left(\mathrm{Ethene}\right)\left(\mathrm{Bromine}\right)(1,2-\mathrm{dibromoethane}) \\ \left(\mathrm{brown}\right) \end{gathered}$$

Ethyne $\left({\mathrm{C}}_2{\mathrm{H}}_2\right)$ changes the color of the solution from reddish-orange color to a colorless solution with the addition of Bromine Water.

The chemical equation of the reaction of Ethyne with Bromine water is written as:

$$\begin{gathered} \mathrm{HC}=\mathrm{CH}\left(\mathrm{g}\right)+{\mathrm{Br}}_2\left(\mathrm{aq}\right)\to \mathrm{BrCH}=\mathrm{CHBr}\left(\mathrm{aq}\right) \\ \left(\mathrm{Ethyne}\right)\left(\mathrm{Bromine}\right)(1,2-\mathrm{dibromoethene}) \\ \left(\mathrm{brown}\right) \end{gathered}$$

Therefore, the alkane is a saturated hydrocarbon and it does not decolorize the Bromine solution.