WILLIAMS and HAMILTON prepared di-n-+lphosphine oxides, but were unable t o isolate any diarylphosphine oxides (e.g., diphenylphosphine oxide).l We have succeeded in preparing diphenylphosphine oxide (I) b y the action of phenylmagnesium bromide on diethyl hydrogen phosphite : (EtO)*PH(:O) --+ Ph,P(:O)-MgBr ---W-Ph,PH(:O) (I)We have shown that diphenylphosphine oxide is in equilibrium with diphenylphosphinous acid (11). Infrared measurements indicate that under normal conditions the phosphine oxide form (I) preponderates. However the aqueous solution reacts quantitatively with silver nitrate solution t o give silver diphenylphosphinite : this reaction is not instantaneous. Diphenylphosphine oxide was oxidised quantitatively in aqueous solution b y bromine yielding diphenylphosphinic acid (111), also produced b y dilute hydrogen peroxide solution or acidified potassium permanganate solution.
When 5.1 g. of I was redistilled after having been stored at 0°for 3 months, 4.9 g. (96%) of I, b.p. 69-71.5°was obtained and 0.1 g. of residue (2%) was left.Adduct of I with maleic anhydride. To 0.98 g. (0.01 mole) of maleic anhydride dissolved in 20 ml. of ether contained in a 125-ml. Erlenmeyer flask was added 0.94 g. (0.01 mole) of I. No heat was evolved and no precipitate formed on standing overnight at room temperature; however, when the solution was cooled in a refrigerator, the adduct crystallized as white needles, 1.90 g. (99%), m.p. 91-92°( petroleum ether, b.p. 30-40°).
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