give a chemical test to distinguish between saturated and unsaturated hydrocarbon
Answers
Hydrocarbons in which all carbon atoms are bonded to other atoms by single covalent bonds are called saturated hydrocarbons. Thus, saturated hydrocarbons do not contain any multiple bonds, including double or triple covalent bonds. In these compounds, each carbon atom is bonded directly to four other atoms. Hence, all carbon atoms are fully occupied by making four bonds. This is why these compounds are called saturated hydrocarbons. Saturated hydrocarbons are the simplest and the least polar organic natural products. Examples of saturated hydrocarbons include alkanes and cycloalkane families of hydrocarbons.
The simplest form of saturated hydrocarbons includes methane (CH4), ethane (C2H6), propane (C3H8) etc. Saturated hydrocarbons burn and give a blue, non-sooty flame in air. Because of the flammability of saturated hydrocarbons that ultimately release a lot of energy, saturated hydrocarbons are often used as a fuel source of vehicle and airplane engines. Well known LPG or cooking gas is also a saturated hydrocarbon called butane (C4H10). The combustion of alkanes with air will result in carbon dioxide gas, water vapor, heat, and light. Hydrocarbons are usually obtained from fossilized plant and animal matter. Once they are obtained as crude oil, the process called distillation is used to separate various products according to their mass. This whole process is called refining of crude oil.
Unsaturated hydrocarbons are the hydrocarbons that contain at least one carbon-carbon double or triple bond in their carbon chain or ring. These compounds have similar physical properties to those of saturated hydrocarbons. However, their chemical properties are much different from saturated hydrocarbons mainly due to the presence of multiple bonds. Usually, chemical reactions initiate from locations where multiple bonds are present in the carbon chain. Hence, the reactivity of unsaturated hydrocarbon increases with a number of multiple bonds present in the main chain.
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By adding cold dilute Baeyer's reagnant
More about Baeyer's Reagnant.
- Baeyer's reagnant is cold dilute
- It is an oxidising agent.
If this mixture is added to an unsaturated compounds such as alkenes or alkanes then :
- Purple colour of changes .
- It is first converted to a green compound which is unstable in alkaline medium.
- This again changes to brown
- The supernatant liquid gets decolourised.
However saturated compounds do not respond to the above test.
In simple words........... your answer is :
In order to test unsaturation first add cold dilute Baeyer's reagnant.
If the reagnant decolorises from purple to colourless then the compound is unsaturated
Otherwise if the reaction does not occur , then it is a saturated compound.
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