Chemical Forums
Chemistry Forums for Students => Organic Chemistry Forum => Topic started by: the_negro_puppy on July 03, 2006, 11:33:41 PM
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What reagents are required, and in what order for this reaction?
Thanks very much for your input and *delete me*
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1-propyl-cyclohexane -> 1-cyclohexyl-prop-2-ene (dehydrogenation)
1-cyclohexyl-prop-2-ene -> required product (using a very weak oxiding agent, such as chromate(VI) in alkali)
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Thanks for the reply!
Would a reagent such as AlCl3 be approriate for dehydrogenation?
Or would FeCl3 be more appropriate?
Thanks
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1-cyclohexyl-prop-2-ene -> required product (using a very weak oxiding agent, such as chromate(VI) in alkali)
1-cyclohexyl-prop-2-ene -----> 1-cyclohexyl-propane-2,3-diol (using a very weak oxiding agent, such as chromate(VI) in alkali)
But the required product is 1-cyclohexyl-ethane-1,2-diol
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1-cyclohexyl-prop-2-ene -> required product (using a very weak oxiding agent, such as chromate(VI) in alkali)
1-cyclohexyl-prop-2-ene -----> 1-cyclohexyl-propane-2,3-diol (using a very weak oxiding agent, such as chromate(VI) in alkali)
But the required product is 1-cyclohexyl-ethane-1,2-diol
I dont understand, thats not what he said at all.
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Yes, I'd say swati is right. the_negro_puppy, could you check whether or not you correctly copied the structures?
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The product in your diagram is 1-cyclohexyl-ethane-1,2-diol.
CH2--CH2 OH OH
/ \ | |
CH2 CH----C---C-H
\ / | |
CH2--CH2 H H
If it was 1-cyclohexyl-propane-2,3-diol, then it would be this...
CH2--CH2 H OH OH
/ \ | | |
CH2 CH-----C---C---C-H
\ / | | |
CH2--CH2 H H H
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The product in your diagram is 1-cyclohexyl-ethane-1,2-diol.
CH2--CH2 OH OH
/ \ | |
CH2 CH----C---C-H
\ / | |
CH2--CH2 H H
If it was 1-cyclohexyl-propane-2,3-diol, then it would be this...
CH2--CH2 H OH OH
/ \ | | |
CH2 CH-----C---C---C-H
\ / | | |
CH2--CH2 H H H
Thanks for the input. The structures i drew are correct, but i cant see anywhere in this thread where anyone mentioned the name of the final product, so im not sure what your talking about.
The problems is completing that synthesis in 3 or less steps, that is:
1-propyl-cyclohexane -> 1-cyclohexyl-prop-2-ene (dehydrogenation) --------> 1-cyclohexyl-ethane-1,2-diol. (Using weak oxidising agent such as Cr(IV) in alkali.
My question is, what exact substances should i use for both the dehydrogenation and weak oxidation.
At the moment im thinking of AlCl3 or FeCl3 for dehydrogenation, and possibly PCC as the weak agent?
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Thanks for the input. The structures i drew are correct, but i cant see anywhere in this thread where anyone mentioned the name of the final product, so im not sure what your talking about.
The problems is completing that synthesis in 3 or less steps, that is:
1-propyl-cyclohexane -> 1-cyclohexyl-prop-2-ene (dehydrogenation) --------> 1-cyclohexyl-ethane-1,2-diol. (Using weak oxidising agent such as Cr(IV) in alkali.
I think after you get allylcyclohexane (1-cyclohexylprop-2-ene) you will need to do something like ozonolysis with a work-up with NaBH4 to get MeOH and 2-cyclohexylethanol and then elimination (dehydration with H2SO4) to get vinylcyclohexane which you can oxidise with OsO4 (or epoxidise with meta-chloroperoxybenzoic acid for example and then react with HO-) to your diol (1-cyclohexylethane-1,2-diol).
Unfortunately that is (at least) four 'steps' :(. Somewhere in your synthesis you must remove a carbon atom from your propyl chain; I don't know what would be the best way of doing it, sorry!
Sorry to correct you but the suggested Chromate(VI) changed to Cr(IV)! ;)
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Please help my exam is tomorrow
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Hi guys, its 12 hours to my final exam and i really need help with this question. I have posted this in a previous thread but forgot to add the Br!
I need to complete this synthesis using any reagents in 3 steps or less
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Thanks very much for your help.
Hmm... that's ever so slightly easier!! ;)
In fact you could probably use the information in the thread here to apply it to the correct question; all you needed to know is how to do the elimination step.
But...
:)
1.) 1-bromo-2-cyclohexyl ethane -----------> 1-cyclohexyl ethene
Dehydrohalogenation using NaOEt and EtOH
2.) 1-cyclohexyl ethene ---------------> 1-cyclohexyl ethane-1,2-diol
Hydroxylation using following reagents
(i) Cold aqueous alkaline KMnO4
OR
(ii) OsO4 followed by hydrolysis
I think that the first step is not so great. Although NaOEt is fine if the primary bromide was more hindered, I just think it isn't hindered enough so you may get a SN2 reaction instead, or both SN2 and E2 reactions. Bases like DBN, DBU, KOCEt3 and KOt-Bu would be better as they are hindered nucleophiles.
Also I would name the product of the first reaction vinylcyclohexane or at least cyclohexylethene; there is no need for the spaces between the cyclohexyl bit and the ethane/ethene bit.
(the_negro_puppy: please stick to one thread for one 'topic (http://www.chemicalforums.com/index.php?topic=9579.0)', and good luck in your exam! :))
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Also I would name the product of the first reaction vinylcyclohexane or at least cyclohexylethene; there is no need for the spaces between the cyclohexyl bit and the ethane/ethene bit.
I agree with your statement & hence modified it as vinylcyclohexane :)
I think that the first step is not so great. Although NaOEt is fine if the primary bromide was more hindered, I just think it isn't hindered enough so you may get a SN2 reaction instead, or both SN2 and E2 reactions. Bases like DBN, DBU, KOCEt3 and KOt-Bu would be better as they are hindered nucleophiles.
Also changed the reagents of first reaction.