Thermal quantities of some cycloparaffins. Part II purification of the samples)

Abstract

Purification of the cyclanes with 4 to 9 C-atoms was effected by fractional distillation. Progress of the purification was checked with the aid of melting curves of the fractions {heat content vs. temperature curves of the melting process). The impurity content of the final samples is estimated at less than 0.2 yo. A fractionating column with a rotating cylinder and a small calorimeter for measurements on melting and transition processes a t temperatures from -180" to +70" are described. 1 . Methods of purification.Whenever possible, the samples obtained in the preparations 1) were first treated with conc. sulphuric acid to remove all impurities except saturated hydrocarbons. Separation from the remaining impurities was performed by fractional distillation. Purification by Mulder's 2 ) method, consisting of successive partial meltings of the frozen sample, each time removing the liquid fraction, was also investtgated for the substances involved here. These experiments in a test model of a self-charging centrifuge, on cyclohexane and cyclooctane to which impurities were added, indicated that only a small purifying effect could be expected. Evidence was obtained that the cyclanes described here, form mixed crystals with small amounts of many substances, cf ").W i t h a view to purifying the cyclanes, with boiling points varying between 12 and 180° C, a fractionating column with a rotating cylinder 4 ) 5 ) having approximately 50 theoretical plates was constructed. Cyclononane, cyclooctane, cycloheptane and cyclohexane, becoming available before the new column, were purified by fractional distillation in column 1 1 ) . In order to obtain the highest possible yield of purest 1) This research was supported by grants from the "Nederlandsche Organisatie voor Zuiver Wetenschappelijk Onderzoek". Part I: Rec. trav. chim. 70, 1033Rec. trav. chim. 70, (1951.