Correlation of the mean‐molecular weights of commercial alkylbenzenes with gas‐liquid chromatographic data

Gas‐liquid chromatography has been used to estimate the mean‐molecular weights of commercial alkylbenzenes of the polypropylene type. Results obtained chromatographically on samples from several sources correlate well with mean‐molecular weight data determined chemically via the sulfonic acids produced from them. The chromatograms are obtained with a 200‐ft. capillary column coated with Apiezon L grease. Partial resolution of the multicomponent mixtures to yield eighty to one hundred peaks, each possibly representing several components, is achieved. A plot of the logarithms of the relative retention times at the median areas of the chromatograms of narrow‐cut distillation fractions of alkylbenzene vs. their known mean‐molecular weights provides a linear calibrating relationship with a discontinuity at a mean‐molecular weight of ca. 260. This discontinuity distinguishes 舠dodecylbenzenes舡 from the higher molecular weight 舠tetradecylbenzenes舡.