Posted by Amy on .
Dehydration of an alcohol has what major project?
This is what I think, does this make sense to anyone?
The major project of dehydration of an alcohol is that alcohol loses a water molecule. An H- and -OH are removed from the adjacent carbon atoms of the same alcohol and end up producing a water molecule. THe result of this is a double bond is formed between the same two caron atoms to produce an alkene product.
Basically don't you mean "product" not project..that doesn't make sense to me anyways if it's "project"
My understanding is this:
1. the alchohol is in a strong acid (for acid catalyzed dehydration [H2SO4 or H3PO4])
2. the oxygen of the OH attacks the H and grabs it.
3. The water molecule then falls off IF it's a tertiary or secondary alchohol. If not well then it has to have something remove a proton from the other adjacent carbon thus creating the double bond and at the same time the water falls off.
4. Due to the water "falling off" so to speak for the tertiary and secondary alchohols, a carbocation is formed (C+). The tertiary carbocation will NOT have rearrangements but the 2ndary will and if it can it will form a tertiary carbocation. (this is a problem in acid catalyzed dehydration)
5. The removal of a H from the carbocation 2ndary or tertiary then produces a alkene. (technically it would be removed by the acid's conjugate base b/c there is no water in the reaction untill it is produced but it is possible for a water molecule to grab the proton and thus become a hydronium ion [H30+])
Thus this is the mechanism but the major product is an alkene
What you said: (my corrections are bolded)
The major project of dehydration of an alcohol is that alcohol loses a water molecule. An H- and -OH are removed from the adjacent carbon atoms of the same alcohol and end up producing a water molecule. No this is not correct. There is a proton (H) that is removed but the OH is not removed on it's own, it's in the form of an H2O after the H is taken from the acid in the solution and added to the -OH of the alchohol. Then after the water forms and falls off of it's own accord (tertiary/secondary alcohol) ..only then is a H removed in addition to the water molecule[or for a primary alchohol H gets removed as the water falls off] THe result of this is a double bond is formed between the same two carbon atoms to produce an alkene product
Hope this helps
I agree with you that project does not make any sense and I feel it should be product. Everyone else thinks so too, but we were told the question is written correctly. We don't understand it either, we think it is a trick question. Thanks for your help I appreciate it.