Part I: A Study of the Catalytic Hydrogenation of Hydroxybenzenes Over Plantinum and Rhodium Catalysts; Part II: The Kinetics of the Acid-catalyzed Hydrolysis of the Dimethyl Esters of Cyclohexanedicarboxylic Acids

Summary: The dimethyl esters of isometric 1,2-, 1,3-, and 1,4-cyclo-hexanedicarboxylic acids have been prepared and the rates of their acid catalyzed hydrolyses in 70 per cent acetone have been determined. All hydrolysis reactions wre run at four temperatures, 25°, 35°, 45°, and 55°. The rate constants for the hydrolyses at each of these temperatures, along with the activation energies for the reactions, have been tabulated in Table IV.

The rates of hydrolysis of the cis-1,3 and trans-1,4 diesters were found to be almost identical. Similarly, the reaction rates of the trans-1,3 and cis-1,4 diesters were found to be nearly the same. The cis- and trans-1,2 diesters reacted at much slower rates.

The relative reaction rates which were determined for the various diesters were taken to be indicative of the predominant inverted isomeric possibilities of the compounds studied. An ester with an exposed carbomethoxyl group would be expected to react at a faster rate than a similar compound whose carbomethoxyl group was not so exposed.

Using this idea, and with the aid of scale models of the various compounds, the results obtained in this work were explained by assuming that in the conformational equilibrium which exists with all the cyclohexane derivatives, the predominant conformation with the cis-1,2, trans-1,3 and cis-1,4 diesters was the axial-equatorial, while with the cis-1,3, trans-1,4, and trans-1,2 diesters the equatorial-equatorial conformation predominated. These similar inverted isomeric states explain the similar reaction rates noted.