Tasks for definition of the substances belonging to the different classes of organic compounds are rather widespread option of control of knowledge and abilities in chemistry. Here it is possible to refer laboratory trial, a task from practical work or theoretical questions with practical orientation in control testing.
It is required to you
- - device with collected ethylene;
- - bromic water or permanganate of potassium;
- - test tubes.
Instruction
1. Several classes of organic compounds belong to unsaturated hydrocarbons, namely: alkenes (ethylene), alkynes (acetylene), alkadienes (butadiene-1.3). They are united that they are characterized by existence multiple (double or threefold) communications. On unsaturated hydrocarbons there are high-quality reactions thanks to which there is an opportunity to distinguish from other classes.
2. The most widespread compound of unsaturated hydrocarbons is the ethylene representing gaseous substance. Considering that this connection has neither color, nor a characteristic smell, visually it is impossible to identify it. Therefore there is a high-quality reaction allowing to define by practical consideration its existence. Ethylene incorporates one double communication. At its introduction with other substances one of communications collapses and in the place of a gap there is an accession of other atoms. Visually it shows experiment on the example of interaction of ethylene with bromic water or solution of permanganate of potassium (potassium permanganate).
3. Take a test tube and pour in it 2-3 ml of bromic water which has brown coloring. Lower in it an exhaust tubule with an ethylene stream. In a few minutes you will see that bromic water became colourless. This experience is confirmation of availability of unsaturated hydrocarbon - ethylene which reacted with bromine with education 1.2 dibromoethanes.
4. That bromic water is extremely toxic agent and in educational institutions it is forbidden for experiments, it can be replaced with the safest permanganate of potassium. In life it is known as margantsovokisly potassium or potassium permanganate.
5. Take a small flask with water, place from it several kristallik of potassium permanganate and stir - solution will get pink coloring. Pour 4-5 ml of the received solution of manganese in a test tube and miss through it an ethylene stream. As a result of reaction, solution of permanganate of potassium will become colourless. It also is a characteristic indicator of availability of unsaturated hydrocarbons to which ethylene belongs. Similarly there is a reaction with alkynes and alkadienes.