New Results for the Dehydration of Methylcyclohexanols

This Spring, a research project was performed by one of my Sophomore Organic Chemistry students. The research project was designed to continue investigations into the dehydration of methylcyclohexanols that we explored Fall 2008. I have written several entries for this project, and will likely write several more. In short, the simple dehydration of an alcohol with a phosphoric acid becomes a very intriguing experiment when the alcohol is a methylcyclohexanol. Multiple alkene products are formed in varying amounts depending on the starting position of the methyl in 1-, 3-, and 4-methyl-1-cyclohexanol. The student wanted to investigate the likelihood that an alcohol ↔ alkene ↔ alcohol equilibrium was being established in the reaction mixture. In once series of inquiries, the dehydration experiment was performed by just refluxing the alcohol without distillation. The reaction mixture showed no signs of other positional isomer alcohols being formed other than the original 4-methyl-1-cyclohexanol. When the reaction was done with only cis or only trans 2-methyl-1-cyclohexanol, no detectable isomerization was observed. Refluxing the alkene with concentrated phosphoric acid did not produce any alcohols. This was rather suprising, since there is nor reason why the reverse equilibriumreaction (acid catalyzed hydration of a alkene) should not happen. The reason we did not observe the hydration reaction may the solubility of the alkene. The series of experiments performed this spring was helpful in a negative short of way – there is no convincing evidence that an alcohol ↔ alkene ↔ alcohol equilibrium is being established.

One Comment

  1. Posted December 9, 2009 at 5:46 am | Permalink

    Nice, new info. Will add to my dehydration site

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