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I'm not an expert teacher or lecturer of chemistry. I was only a student from SMA NEGERI 15 SURABAYA who had been one of the Bronze Medalist Participants of Olimpiade Sains Nasional X (2011) of Chemistry In Manado, North Sulawesi, 11 - 16 September 2011 and graduated in 2012. Now, I'm studying at Universitas Airlangga in Surabaya, Indonesia. I do love chemistry and I would like to help them who had difficulties in studying chemistry. That's why, please understand me if you found some misconcepts in my entries. Suggestions are always necessary in order to develop this blog. And I'm sorry because my English isn't so well.

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The Documents

Wednesday, December 21, 2011

Reaction Mechanisms Introduction: Dehydration of Alcohols

We need to know why when we heat ethanol with concentrated sulfuric acid at 180 oC, we will get ethene. We need to know why when we heat 3-methyl buthan-1-ol with concentrated sulfuric acid at 180 oC, we will get so many kinds of products. What makes it happened? To answer this question, scientists found a way to explain this phenomenon: Reaction Mechanism.

In organic chemistry, reaction mechanism is a method to understand how what happen if we mix 2 or more kinds of compounds. Electrons always move, not just standing in its position. This is the important key to understand reaction mechanism. The picture below will explain us:



From the reaction mechanism above, we now learn that sulfuric acid here acts as catalyst and dehydrator.

Now, the picture below will explain why 3-methyl buthan-1-ol gives so many products when it is dehydrated (and of course all products has its own yield).


With reaction mechanism, we can predict the products of simple organic reactions. From the picture above, we now learn by the reaction is in process, there are carbocations will be formed. We also learn that to neutralize the carbocation formed, compound can release its hydrogen as hydrogen ion or the hydrogen can move as the hydride ion to form a more stable carbocation (Hydride Shift) and then the hydrogen is released as hydrogen ion.

The most dominant compound formed from the reaction above is 2 - methyl - 2 - buthene. The Saytzeff rule is the reason for this problem.

We have to have so many practices in order to improve our skill in organic chemistry reactions and remember: Experience is the best teacher.

Source:
Documents of Pelatnas I IChO 2012


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