Dehydrogenisation der stereoisomeren Dimethyl‐cyclohexane; Kontakt‐Umlagerung der cis ‐in die trans ‐Formen

Sterochemistry and Heterogeneous Catalysis

“…It appears that at temperatures greater than about 90°C., racemization ensues whenever the hydrogen atom at the tertiary position is exchanged. This heterogeneous catalytic racemization is related to the cpimerizations of dialkylcyclohexanes reported earlier (210). cis-l,2-Dimethylcyclohexane and cfs-1,4dimethyl cyclohexam; are converted into the trans forms upon passage over nickel in a stream of hydrogen at 175°C.…”

Sulfuric Acid Isomerization of Methylalkanes, Dimethylalkanes and Dimethylcyclohexanes

“…The composition of the mixtures of cis and trans isomers for 1,4-dimethylcyclohexane, 1,2-dimethyIcyclohexane and 1,3-dimethylcyclohexane are plotted against time in Figs. 6,7 and 8. Only in the case of 1,4-dimethylcyclohexanes was equilibrium established by starting with -Equilibrium composition of cis-and trans-l ,4dimethylcyclohexane at 25°: starting with: , trans-1,4dimethylcyclohexane ; •, cis-1,4-dimethylcyclohexane; also formed: , cis-l,3-tiiinethyleyeluhexane; , trans-l ,3-dimcthylcyclohexane.…”

Studies in the Polyoxyphenol Series: V. Preparation From Pyrogallol of the Isomeric Cyclohexane-1,2,3-Triols and -1,2-Diols, and of Several Isopropylidene and Monomethyl Derivatives

“…Although such a thermal isomerization actually took place when cis-1,2-dimethyl cyclohexane was passed over nickel a t 1'70°C. (18,27), a keto-stage mechanism seemed more probable in the present case because Coussemant and Jungers (6) isolated up to 18% of cyclohexanone a s an intermediate in the high pressure hydrogenation of phenol. T h e recovery of cis-cis-cis-cyclohexanetriol exclusively from the hydrogenation of optically active cis-2,3-dihydroxycyclohexanone over platinum oxide (23), however, raised an objection to this analogy.…”