SIR: The determination of the oxirane ring in organic compounds has generally involved reaction with excess hydrochloric acid in a vayiety of solvents. Because the reaction LS slow, a t least a 15-minute reaction time is generally allowed before back titrating the excess acid. The determination of aziridines also requires back-titration techniques (1, 4) . Durbetaki (2) described a direct titration of epoxies with anhydrous hydrogen bromide in acetic acid. While this method is rapid and capable of good results, the reagent, which fumes profusely in air, requires special handling and freque it restandardizations for accurate analyses, The following method employs a stable, readily available, titrant which can be used for the direct titration of oxiranes and certain aziridines. The sample is dissolved in chloroform and titrated to a crystal violet end point with standard perchloric acid (in acetic acid or dioxane) in the presence of an excess of a soluble quaternary ammonium bromide or iodide. For epoxides eithereagent can be used, but the quaternary bromide is satisfactory for virtually all the materials usually encountered and is recommended over the iodide because of economy and better cd,orability. With aziridines, however, the iodide is preferred as it gives more rapid reactions and sharper end point3.

Direct Titration of Epoxy Compounds and Aziridines.

Methylosinus trichosporium OB3b biosynthesizes a broad specificity soluble methane monooxygenase that rapidly oxidizes trichloroethylene (TCE). The selective expression of the soluble methane monooxygenase was followed in vivo by a rapid colorimetric assay. Naphthalene was oxidized by purified soluble methane monooxygenase or by cells grown in copper-deficient media to a mixture of 1-naphthol and 2-naphthol. The naphthols were detected by reaction with tetrazotized o-dianisidine to form purple diazo dyes with large molar absorptivities. The rate of color formation with the rapid assay correlated with the velocity of TCE oxidation that was determined by gas chromatography. Both assays were used to optimize conditions for TCE oxidation by M. trichosporium OB3b and to test several methanotrophic bacteria for the ability to oxidize TCE and naphthalene.

Optimization of trichloroethylene oxidation by methanotrophs and the use of a colorimetric assay to detect soluble methane monooxygenase activity

Amine loaded zeolites for carbon dioxide capture: Amine loading and adsorption studies

Potentiometric Titration of Salts of Organic Bases in Acetic Acid

The presence of an aziridine ring in mitomycin C suggests that the mechanism of action of the antibiotic is like that of the antitumor alkylating agents. However the compound is unexpectedly stable during aerobic incubation with rat liver homogenates although rapidly metabolized anaerobically. Mitomycin is not reactive with gamma-(4-nitrobenzyl) pyridine and reacts only slowly at acid p(H) with thiosulfate. It is proposed that mitomycin is activated in vivo, possibly by a reduction which "unmasks" the potential activity of the fused aziridine ring.

William. Seaman

Papers

Acid-Base Titrations in Glacial Acetic Acid. Acid Potassium as Primary Standard and Behavior of Crystal Violet Indicator

Method of Assay for Ethylenimine Derivatives

Coulometric Titration of Dyes with Externally Generated Titanous Ion

Collumetric Titrations with Low-Inertia Integrating Motor

Spectrophotometric Determination of 1-Naphthol in 2-Naphthol Utilizing Difference in Reaction Rates