Experiences

Alkadienes

Mária Fabianová

Slovakia

Lower Secondary School

Chemistry

Teaching in class

Direct

Alkadienes are hydrocarbons, molecules of which contain two double bonds. The topic of hydrocarbons is so large that it is impossible to teach everything which is also thanks to the fact that allowance fell to the tenth. It is very difficult to choose the facts which will be taught, but in any case it is not possible to maintain the context that is necessary so at least I choose the compounds which had played a significant role not only in the history of science but also in ordinary life.
A compound which is one of the hydrocarbons is 2-methyl-1,3-butadiene, commonly called isoprene which is an essential building block of natural rubber.
In Brazil grew trees (Hevea brasiliensis), cutting the bark of which oozed white liquid – latex. By its further processing was obtained a compound that was named natural rubber. Owners of rubber tree plantations very soon understood how important that compound is because by the beginning of 19th century was Europe and the United States swept by madness. That is why it was prohibited to export the seeds of rubber tree from the country. Obviously it was not possible to control it completely and rubber tree started to be grown also in other tropical areas. India rubber was resilient, flexible and water resistant but it started to break under the lower temperature and melt under the high temperature.
Charles Goodyear was one of the hundreds of people who have tried to solve these problems.
In 1770 one of the chemists discovered that it is possible to erase the text written by pencil with the pieces of dried latex. That is when the word “rubber” was created which is now so ordinary that no one thinks where it comes from.
Goodyear stubbornly tried to maintain the properties of Indian rubber. We can say that he had no financial resources and one of the creditors had him locked up in the prison for debtors where he took also a few pieces of rubber and his wife’s rolling pin. It last for many years when he added various substances to the rubber but he did not maintained the properties wanted.
Once when he added sulphur to it he thought that he finally reached the success but it turned up that something is still missing. There is many of the versions which say how Goodyear discovered the vulcanization of rubber by accident. One of them says that he threw up his hands and the rubber he held in hand landed on the furnace. Finally he discovered how to make a rubber, first step was to add sulphur. The whole process is known as vulcanization of rubber.
We do not perceive it but without rubber would our way of existence had looked otherwise – tires of cars. In the early 19th century when the means of transport was a carriage with horses, urban residents complained about the noise it caused.
In extension to tires the rubber has also other extensive utilization and according to it are added various substances to it.
Goodyear’s effort, his previous knowledge and admirable persistence could be an inspiration but I think that it is not. Students take everything for granted, they probably think that everything here has been around since the creation of world. It is not possible to deal with history of each discovery but textbooks for high schools do not mention the people which are behind the facts and the form of our contemporary world.
I consider this experience to be positive.