No abstract

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The ability of certain nitrogen bases to form addition compounds with Lewis acids (electron-pair acceptors) is well known. Reactions of this type in the case of chromium(V1) oxide are complicated by the fact that the oxide is a strong oxidizing agent. Procedures are given here for the preparation of three typical compounds : pyridinechromium(V1) oxide, 2C5H5NCrO3; 3 (or p)-picoline-chromium(V1) oxide, 2CsH7N-Cr03; and 4(or y)-picolinechromium( VI) oxide, 2CsH7N. Cr 0 3. ProcedureFour grams of chromium(V1) oxide (0.04 mol) is dried at 110" in 2rucuo for 4 hours and is then cooled in an ice-salt mixture. Fifty milliliters of pyridine (0.63 mol) is also cooled in a 300-ml. Erlenmeyer flask. While the 50 ml. of pyridine is shaken in the flask immersed in an ice-salt-water mixture, the chromium(V1) oxide is slowly added. The flask is stoppered, and the mixture is agitated until all solid particles have dissolved. A larger amount of pyridine may be used to hasten solution, if desired. Cooling is necessary, since the reaction generates enough heat t o bring about oxidation of the pyridine unless the temperature is controlled.