David W. Emerson

A Versatile One‐Pot Synthesis of Dialkyl Disulfides and Sulfides

Abstract Conversions of monofluoroalkyl and alkyl bromides to the corresponding dialkyl disulfides in a one‐pot synthesis using thiourea followed by basic hydrogen peroxide are described. Modified methods afford access to unsymmetrical disulfides and sulfides.

On-line dechlorination-hydrogenation of chlorinated paraffin mixtures using GC and GC/MS.

Chlorinated paraffins (CPs) are straight chain hydrocarbons that are produced as complex mixtures and are used as flame retardants and paint additives. These mixtures are extremely difficult to characterize using conventional chromatographic methods, as conventional gas chromatography results in unresolved complex chromatograms that preclude the identification and quantification of individual congeners or any reasonable assessment of the average carbon chain length. Carbon chain length is an important parameter for assessing physical properties and the toxicity of these materials. We have modified and improved a previously published gas chromatography–flame ionization detector method that uses Pd catalyst held in the gas chromatograph injector to simultaneously dechlorinate the CPs and separate the resulting alkanes. In addition, we have adapted this method to gas chromatography–mass spectrometry. Dehalogenation of other compounds was also studied with this system to investigate potential application to other complex halogenated mixtures.

Determination of active chlorine in air by bonded phase sorbent collection and spectrophotometric analysis

The development and application of a collection method for total combined gas-phase active chlorine (i.e., Cl2, HOCl and chloramines) based on a sulfonamide-functionalized silica gel sorbent are presented. Preparation methods for the sorbent are described, as are procedures for chemical and physical characterization, such as chlorine capacity and chlorine collection efficiency. For determination of the collected chlorine, a modified version of the N,N′-diethyl-p-phenylenediamine (DPD) colorimetric method was employed, which yielded a detection limit of 0.1 µg of chlorine. At flow rates ranging from 31 to 294 ml min–1, the collection efficiency was >90% based on breakthrough analysis. Recovery of chlorine spikes from 0.05 g aliquots of the sorbent was not quantitative (≡60%) but was reproducible; the recovery is accounted for in samples by adding weighed amounts of sorbent to the standards. Analytical data for active chlorine concentrations (i.e., Cl2 + HOCl) above a swimming pool are presented.