Arbacluce
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Failed synthesis of cyclohexanol from cyclohexene.
Hi(sorry for my english)
I performed a reaction of conversion of cyclohexene to cyclohexanol using water and sulfuric acid that ended in failure. The yield was almost 0%(NMR
spectrum). I have found papers where yields of cyclohexanol were around 15-25%(5% using only water and acid) but they use zeolites as catalysts and
several organic solvents as additional help, so hydration reaction using water and sulfuric acid should be exrtremely inefficient, so I should obtain
almost no product. Is hydration reaction of alkenes always that bad? If no, what is the reason for the failure?
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Chemi Pharma
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I read somewhere you need to keep the mixture of cyclohexene and dilute sulfuric acid undisturbed for a week, before distill the cyclohexanol. Seems
like the hydration take a long time to proceed at normal conditions.
Cause of this, the reaction is generally catalysed by zeolites and/or ionic columns changers.
Some studies claims that you'd better esterificate cyclohexene with formic or acetic acid and further hydrolize the ester in acidic media at reflux to
obtain cyclohexanol on demand with good yield.
[Edited on 30-4-2018 by Chemi Pharma]
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DIBALL
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Maybe not a "clean" suggestion, but couldn´t you react it with some halogen like Br2 in an aqueous solution and then let it react with an excess of
NaOH?
Messy, but probably a better yield...
EDIT: Just realized, that the result would be cyclohexEnol. But don´t know what you are using it for, so it might be still good.
HBr with a peroxide and then NaOH might be an option too for cyclohexanol
[Edited on 2-5-2018 by DIBALL]
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JBSC
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to chemi pharma
chemi pharma........you said "Some studies claims that you'd better esterificate cyclohexene with formic or acetic acid and further hydrolize the
ester in acidic media at reflux to obtain cyclohexanol on demand with good yield.". WHAT DOES THAT MEAN? I mean esterificate to me means to make an
ester. How do you do that with an alkene and a carboxylic acid? I love the advice about letting it sit for a week if you have no zeolites. I
always thought the hydration of an alkene was a pretty low energy reaction. I guess at least one hump is high energy to get over. I never did the
reaction. So far i have always gone the other way. Making an alkene from an alcohol.
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JBSC
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to DIBALL
DIBALL............I THINK..... MAYBE......... if you add an alkene to Br2 in H2O then you would make hypobromous acid with the Br2 and H2O and that
would react with the alkene to make a halohydrin..... meaning a bromine on one carbon and water(OH) on the other carbon where the double bond used to
be. Then if you used NaOH to do an SN reaction with the halogen part of the halohydrin then you would have a 1, 2 diol wouldn't you? ALSO......i
think MAYBE if you did make cyclohexENOL then it would equillibriate to form cyclohexanone. I like the HBr/ peroxide then NaOH SN reaction idea
though. That is on my list of things to try to make.......an ALKYL PEROXIDE so i can do the reaction you are suggesting with HBr/peroxide and an
alkene. Not that far in my experiments though. I am still trying to figure out how to do an SN reaction with NaOH and an alkyl bromide. SO far i
tried a few different ways but no luck
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CuReUS
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Quote: Originally posted by DIBALL  | couldn´t you react it with some halogen like Br2 in an aqueous solution and then let it react with an excess of NaOH?
EDIT: Just realized, that the result would be cyclohexEnol. |
Actually,you would get the diol,since the alkene addition takes preference over allylic substitution if Br2 is used.https://www.masterorganicchemistry.com/2013/11/25/allylic-br...
| Quote: | | HBr with a peroxide and then NaOH might be an option too for cyclohexanol |
Just HBr is enough.Or even better,HCl 
Your idea isn't that bad,I was going to recommend the same thing myself
like this https://www.researchgate.net/publication/263386338_Esterific...
only problem is that you have to use another catalyst here.
JBSC- do you need cyclohexanol or cyclohexanone ? because you can convert cyclohexene to ketone directly
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Chemi Pharma
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| Quote: Originally posted by JBSC | | chemi pharma........you said "Some studies claims that you'd better esterificate cyclohexene with formic or acetic acid and further hydrolize the
ester in acidic media at reflux to obtain cyclohexanol on demand with good yield.". WHAT DOES THAT MEAN? I mean esterificate to me means to make an
ester. How do you do that with an alkene and a carboxylic acid? I love the advice about letting it sit for a week if you have no zeolites. I
always thought the hydration of an alkene was a pretty low energy reaction. I guess at least one hump is high energy to get over. I never did the
reaction. So far i have always gone the other way. Making an alkene from an alcohol. |
I understand your surprise. I was surprised too when I read about this strange kind of reaction. It's strange, but it's real, that formic and acetic
acid reacts with alkenes to form esters.
Let's see Wikipedia at: https://en.wikipedia.org/wiki/Formic_acid
"Addition to alkenes
Formic acid is unique among the carboxylic acids in its ability to participate in addition reactions with alkenes. Formic acids and alkenes readily
react to form formate esters. In the presence of certain acids, including sulfuric and hydrofluoric acids, however, a variant of the Koch reaction
occurs instead, and formic acid adds to the alkene to produce a larger carboxylic acid.[35]"
And more, see the research at: https://pubs.acs.org/doi/abs/10.1021/ie060781y?src=recsys&am...
"Cyclohexanol Production via Esterification of Cyclohexene with Formic Acid and Subsequent Hydration of the Ester Reaction Kinetics"
See also the paper I attached below:
Attachment: alkene esterification with formic acid and hydrolisys to alcohol.PDF (147kB)
This file has been downloaded 369 times
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Magpie
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I could find the OP's synthesis neither in OrgSyn nor in Vogel. I'm wondering if this reaction is just too slow to be practical.
The single most important condition for a successful synthesis is good mixing - Nicodem
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