Organic chemistry (1)

Draw the answer? Do you mean how to work out the answer?

2011-10-03 17:27:00 補充：
I think it is something similar to the "Rhenium-Catalyzed Didehydroxylation"

2011-10-03 19:44:37 補充：
I think Rhenium-Catalyzed didehydroxylation is not included in AL/DSE syllabus.
It is about changing vinical diols to alkenes with presence of rhenium-containing complex, as catalyst.

By the way, what exercise are you doing? It's quite interesting......

2011-10-03 23:02:17 補充：
Oh I see, analytic chem, I don't know much about this topic, maybe I will do some searching first. Hope I can answer you later.

2011-10-03 23:05:23 補充：
Is this the answer? If yes, would you mind giving me the question? Thx!

2011-10-04 17:51:04 補充：
Oops, I've got wrong. This reaction is NOT Rhenium-Catalyzed Didehydroxylation.

It should be a dehydration.

First, look at the reactant,

圖片參考：http://imgcld.yimg.com/8/n/HA00656648/o/701110020111613873470740.jpg

It can be also written as follow:


圖片參考：http://imgcld.yimg.com/8/n/HA00656648/o/701110020111613873470751.jpg



With conc. H2SO4 and heat, the squared hydrogens and -OH groups will form the water produced in dehydration (red H with red OH and orange H with orange OH)

圖片參考：http://imgcld.yimg.com/8/n/HA00656648/o/701110020111613873470752.jpg

Since the C-H bonds and C-O bonds undergoes homolytic fission, the remaining electrons on the four carbon atoms form double bond with each other.

You can see the mechanism I deduced below (sorry for bad drawing):


圖片參考：http://imgcld.yimg.com/8/n/HA00656648/o/701110020111613873470763.jpg
Ask if you have any problem.

2011-10-04 22:11:12 補充：
Just typo, exchange the OH group and H in either one colour is okay.
Mechanism is similar.

2011-10-04 22:12:09 補充：
For the book, I think we have been talking about different publishers.

2011-10-04 22:18:25 補充：
I think you have done part(a), right?
So, part(b) is just as what I have answered, be aware of the typo is okay.
Feel free to ask if you have any more question.

2011-10-06 18:47:47 補充：
For the question at
http://i453.photobucket.com/albums/qq252/tomchan1216/Chem3.jpg , it is the problem of stability.

The major product, cyclohexa-1,3-diene, is similar to benzene, the electrons at C=C bonds can move to the neighbour C-C bonds repeatedly, forming resonance.

2011-10-06 18:48:14 補充：
But for the other, cyclohexa-1,4-diene, the double bonds are opposite to each other, the electrons are less likely to move around, within the carbon ring.

This made cyclohexa-1,3-diene more stable than cyclohexa-1,4-diene.

2011-10-06 18:48:45 補充：
So, the product tends to adopt the structure of cyclohexa-1,3-diene instead of cyclohexa-1,4-diene. Thus, the major product will be cyclohexa-1,3-diene

yes, please refer to the product side.

2011-10-02 21:25:40 補充：
but my question is how to draw the answer... my exercise does not have a full explanation.

2011-10-03 17:54:12 補充：
yeah i mean how to work out the answer...
what is the term Rhenium-Catalyzed Didehydroxylation? is it in AL/DSE syllabus...?

2011-10-03 21:03:39 補充：
Success Key for HKDSE Book 7

2011-10-04 19:43:46 補充：
the positions of hydroxyl groups got some problem...?

book 7 is organic chem~ book 10 is analytical chem
the question will be sent to u later~

2011-10-04 22:20:48 補充：
One more question:
http://i453.photobucket.com/albums/qq252/tomchan1216/Chem3.jpg

Thanks for your help.

Isn't the product drawn in the question already???