Dehydration of Methylcyclohexanols V

The dehydration of methylcyclohexanols provides a fecund problem to explore. The key is to develop methods to determine the distribution of alkene products in terms of % total alkenes. There are four possible positional isomers: I. methylenecyclohexene (Aldrich, Acros 1192-37-6); II. racemic 3-methyl-1-cyclohexene (Acros, 591-48-0); III. 1-methyl-1-cyclohexene (Aldrich, Acros 591-49-1) IV. racemic 4-methyl-1-cyclohexene (Aldrich, Acros 591-47-9). Two of the alkene positional isomers contain an asymmetric carbon.

The obvious place to start is by studying how the alcohol structure affects the product distribution of alkenes. There are 5 positional isomers of methylcyclohexanol: I. cyclohexanemethanol (Aldrich 100-49-2); II. 1-methylcyclohexanol (Aldrich 590-67-0); III. racemic cis&trans 2-methylcyclohexanol (Aldrich 583-59-5) IV. racemic cis&trans 3-methylcyclohexanol (Aldrich 591-23-1) V. cis&trans 4-methylcyclohexanol (Aldrich 589-91-3). Three of the alcohols are present in cis and trans diastereomer pairs: cis 2-methylcyclohexanol (Aldrich 7445-70-1) trans 2-methylcyclohexanol (Aldrich 7445-52-9) cis 3-methylcyclohexanol (5454-79-5) trans 3-methylcyclohexanol (7443-55-2) cis 4-methylcyclohexanol (Aldrich 7731-28-4) trans 4-methylcyclohexanol (Aldrich 7731-28-4). In addition there are 4 entaniomer pairs among the alcohol starting materials. Most of them are commercially available, for a price.

mch_scheme-2

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