Chemical Forums
Chemistry Forums for Students => Organic Chemistry Forum => Topic started by: fionnn on May 18, 2020, 02:08:56 PM
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How does cyclohexanol react with bromine?
I am faced with a problem of reacting cyclohexanol, cyclohexene and phenol with bromine (Br2) to achieve a bromine substitution on the ring (each reaction individually) and illustrating the mechanisms and isomers etc.
For cyclohexene and phenol this is pretty straight forward. However, I am struggling with the reaction with cyclohexanol, is it possible to just go and straight up substitute it so that Cyclohexanol + Bromine -> Bromocyclohexane + HOBr as when I search this up there are no results.
I considered reacting the cyclohexanol with phosphorus tribromide and that is still a option I think, but I'm not sure if I'm supposed to take the question literally and only react them with Br2.
Any thoughts or suggestions on whether I can react it directly (there's no lab setting here just on paper) or I should stick with the reaction with phosphorus tribromide.
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I can imagine one possibility (and I am not even sure that it would work), but it is difficult to supply only a hint. The best that I can do is to suggest that you think outside of the box in the sense of considering a range of what bromine can do chemically.
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Ay it's more of an interpretation problem with the question to be honest, it states "under a range of conditions to achieve a bromine substitution", so I guess interpreting that range of conditions as firstly reacting the bromine with phosphorus to create the phosphorus tribromide to then react with the cyclohexanol is probably the way forward.
Thus giving me an SN2 nucleophilic substitution reaction to work with (bond formed between the O and the P, creating a Br anion which attacks the bond between the C and O on the ring, giving me the bromocyclohexane and then phosphorus acid as a by-product.
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Actually I think I've been a bit of an idiot with this reaction.
Surely I can just react the cyclohexanol with HBr (formed from the reflux of sodium bromide and sulfuric acid) to then create bromocyclohexane and water as a by product (with it being nucleophilic substitution).
Anybody care to confirm this?
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I interpreted the question to mean that the source of Br atoms was solely Br2. What chemical properties would you ascribe to elemental bromine?
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I'm thinking maybe free radical substitution?
Homolytic fission of the Br2 to make 2 free radicals, one of which collides with a C-H bond on the cyclohexane ring and forms HBr, then the second free radical forms a bond with the C to make 2-bromocyclohexanol?
i.e. Br2 :rarrow:2Br·
C6H11OH + Br· :rarrow: C6H10OH· + HBr
C6H10OH· + Br· :rarrow: C6H11BrOH
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That looks reasonable. I was thinking along different lines, of bromine first as an oxidant.