Spot Tests in Organic Analysis

Abstract

the investigation, although its influence was not specifically studied. The effect of light on the reaction can be seen by comparing the following relative values which were obtained by folding identical lauroyl peroxide-containing reaction mixtures: (a) in the dark (64% T), (b) under fluorescent lamp (54% T), and (c) in direct window light (30% T). Light also affected the A/,Ar-dimethyl-p-phenylenediamine reagent solution in the same manner. Reagent solutions were, therefore, prepared fresh daily and held in the dark. Reactions were carried out in subdued light, not total darkness. The color failed to develop in the presence of dicumyl peroxide even when Fe, Co, and rare earth naphthenates were present as catalysts. The effects of metallic naphthenates were not tested with lauroyl or benzoyl peroxide. Steric hindrance is thought to be responsible for failure of dicumyl peroxide to catalyze the color reaction. The reaction appears to be: Reagent-f-aqueous CHsOH-* blue complex. This reaction is greatly accelerated by the presence of lauroyl or benzoyl per-oxide. Although the reaction mechanism is not known, it does not appear to be a simple oxidation, but rather cata-lyzed by a free radical mechanism, probably involving the splitting off of-N §h! groups by active OH. The calculated precision of the method is ±4.1% at the 95% confidence limit based upon eight determinations for each peroxide. LITERATURE CITED (1) Eiss, M. I., Giesecke, P., Anal. Using a combination of high temperature gas chromatography and mass spectrometry, 67 compounds present in a refined paraffin wax were identified. The gas chromatography unit utilized two different columns operating at 300° C. to separate hydrocarbon types. The first column, containing a microwax residue liquid phase, separated n-paraffins (ad-mixed with 1-cyclopentyls), iso-paraffins, and 1-cyclohexyls. The second column, containing a packing coated with an asphaltene residue, separated the n-paraffins and the 1-cyclopentyls. The method takes advantage of the extreme regularity in boiling point which exists within each homologous series of hydrocarbons in paraffin wax. In addition, the number of compounds to be determined is relatively small because of the removal of the lower melting branched structures through wax refining processes. The compounds identified consisted of C20 to C32 homologs of n-paraffins, 1-cyclopentyls, 1-cyclo-hexyls, 2-to 5-methyls, 1-phenyls, and mono-and dimethyl cyclic compounds. The application of gas chromato-graphic (GC) techniques to a study of hydrocarbons in the paraffin wax range has been limited by the very severe requirement for high thermal stability and good selectivity of the stationary phase at 300° C. Exploratory work by Ogilvie, Simmons, and Hinds (S) showed that with asphaltenes as a stationary phase it was possible to obtain reliable normal paraffin analysis. In their chromatograms, however, the isoparaffins and cycloparaffins were smeared under the n-paraffin peaks and were essentially unresolved. In the present work three stationary phases have been evaluated for use at 300° C. These were molecular distillation bottoms of a microcrystalline wax, a petroleum derived asphaltene fraction, and an aromatic extract of a residual stock. By using microwax bottoms and as-phaltene columns in combination, the authors were able to resolve n-paraffins, isoparaffins, 1-cyclohexylparaffins, and 1-cyclopentylparaffins into distinct peaks. To help identify these peaks, pure hydrocarbons from API Project 42 were run as relative retention volume (R.R.V.) standards. In addition, fractions corresponding to these peaks were collected and analyzed by mass spec-trometry (MS). EXPERIMENTAL