No abstract

Hexacyclic polynuclear hydrocarbons are of interest to air pollution because of their carcinogenic activity and their presence in combustion sources.An investigation was made of both the one-dimensional and two-dimensional thin-layer chromatographic separation of these compounds using mixed substrates. Spectrophotofluorometry was used for identification and estimation purposes. Dibenzo(o,e)pyrene was identified as being present in urban airborne particulate matter obtained from composites of samples from the city of Birmingham and from a combination of various other cities in the state of Alabama. The concentration of dibenzo(a,e> pyrene in the composite from the combination of various cities in Alabama was estimated to be approximately 100 pg.per gram of benzene soluble.

A series of 1, l-diaryl-2-bromoethenes was synthesized and allowed to react with potassium ¿-butoxide in anhydrous diglyme at 0°. The substitution products were isolated by solvent extraction and column chromatography and identified by nuclear magnetic resonance spectrometry and elemental analysis. The elimination-rearrangement products were identified by ultraviolet spectrophotometry. The rate constants for the rearrangements step were calculated by the time-ratio method. An increase in electron-withdrawing character of the substituent caused the elimination-rearrangement reaction to proceed slower and the substitution reaction to proceed faster. None of the compounds tested underwent both reactions. The Hammett reaction constant, p, was found to be

NOTES 75 1 Notes THE DETERMINATION O F URANIUM METAL I N PRODUCTS FROM THE REDUCTIONO F URANIUM OXIDES WITH MAGNESIUM IN the production of uranium metal by the reduction of uranium oxides with magnesium, it is necessary to determine the amount of metal in the reduction product in order to determine the efficiency of the reduction. The reduction product has been shown to contain, as well as uranium metal, significant amounts of uranium oxides (UO, and U,O,), uranium carbides, magnesium uranates, magnesium metal and magnesium oxide. Because of the rather complex nature of this product, a procedure employing either the solubility or insolubility of the metal or the other constituents of the product appeared to offer the most promising approach.The solution of uranium metal in bromineethyl acetate solutions under reflux has been described.1 This solvent system has been found satisfactory for the extraction of uranium metal from samples of reduction products.

An accurate, sensitive spectrophotometric method has been developed for determining alkylating agents. The method involves the alkylation of 4-picoline at 100" C in 2-methoxyethanol, with subsequent reaction of the 4-picolinium cation with a-dinitrobenzene in the presence of alkali to produce the chromogen. With 2-phenylethanol as the solvent, the method is autocatalytic a t 100" C. The variables in the procedures were studied, and the methods were compared to one another and to methods in the literature. Some preliminary studies of other possible methods for alkylating agents are discussed.ALKYLATING agents have been shown to be present in urban air, in air polluted by various sources, in automobile exhaust and in cigarette tar.l Many pesticides, chemical carcinogens and anticarcinogens are alkylating agents, as pointed out previous1y.l More recently, the carcinogenic properties of alkylating agents such as nitrogen mustards, sulphur mustards and alkanesulphonate esters,2 epoxides, ethyleneimines and lac tone^,^ y3 and nitroso compounds4 have been reviewed. The anti-fertility effects of alkanesulphonate esters have been s t ~d i e d , ~ and alkylating agents synthesised as possible an ti-carcinogens have been surveyed.6,7,8,9The spectrophotometric determination of alkylating agents has been accomplished by using a substituted-pyridine reagent such as 4-(li-nitrobenzyl)pyridine.lD This reagent reacts with alkylating agents to produce a substituted N-alkylpyridinium cation.The 4-(4-nitrobenzyl)pyridine procedure has been used in both its originaPJ1,123 and autocatalyticl forms to determine many alkylating agents. The sensitivity of the original 4-(4--nitrobenzyl)pyridine procedurelo is relatively low (molecular extinction coefficient of 7300). Several autocatalytic methods, in which various hydrazones were used, have produced high sensitivity, with molecular extinction coefficients as high as 1,500,000 for some alkylating agents.l These procedures, however, yield a poorer reproducibility than the present method, do not obey Beer's law for alkyl iodides, and require a special high-temperature (180" C) bath.In this study, an accurate, sensitive, reproducible method that obeys Beer's law and that utilises a readily available boiling-water bath has been developed. The method involves the alkylation of 4-picoline and the subsequent reaction of the 4-picolinium salt with o-dinitrobenzene. The method can also be used autocatalytically at 100" C. The non-catalytic and autocatalytic methods are compared with one another and with methods from the literature. Some preliminary experiments involving possible future methods for alkylating agents are discussed.