Chloroethyl Dichlorophosphite

Submitted bt Donald Ray Martin, W. Douglas Cooper, Dwight R. SPESSARD,t AND HaROLD SlMMONS BoOTIlf Checked by T. M. Beck and E. N. Walsh  

The reaction between an alcohol and the halide of a non-metal (usually phosphorus) is well known in the synthesis of alkyl halides. Usually the reaction is conducted with an excess of alcohol and/or in basic media thus 

Until recent years, comparatively little attention has been given to the inorganic products of these reactions. By maintaining an excess of the nonmetallic halide, stepwise replacement of a halogen atom by an alkoxy radical may be achieved. 

In this synthesis, the reaction is confined primarily to the first step by adding 1 mol of ethylene chlorohydrin to 1 mol of precooled phosphorus(III) chloride. 

2-Chloroethyl dichlorophosphite may also be prepared by allowing ethylene oxide to condense with phosphorus(III) chloride.1 

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The apparatus and procedure for the preparation of 2-chloroethyl dichlorophosphite are essentially the same as described for the analogous silicon and sulfuryl compounds (synthesis 30). One hundred thirty-seven and one-half grams of reagent-grade phosphorus (III) chloride (1.0 mol) is allowed to react with 80.5 g. of freshly distilled, anhydrous ethylene chlorohydrin (1.0 mol) in a 500-ml. flask under the conditions set forth in the cited synthesis. Approximately 1 hour is required for the introduction of the ethylene chlorohydrin. 

Chloroethyl dichlorophosphite is a colorless liquid having a specific gravity of 1.515 at 0°. It solidifies to a white solid at —142 1°. A second crystalline phase may be obtained by allowing the first phase to warm to room temperature. The higher-melting phase was not obtained directly from the liquid phase, nor was a definite temperature for the transition between the two phases observed. The boiling point has been reported to be 172 to 175° (747.8 mm.)1 and 162.4° (760 mm.).2... 

Chloroethyl dichlorophosphite fumes in moist air and hydrolyzes readily in water. It reacts vigorously with ethanol and propylene glycol and is soluble in dioxane, acetone, and diethyl ether. 2-Chloroethyl dichlorophosphite is obtained when the dichloride is allowed to react with antimony (III) fluoride at room temperature under a pressure of 50 mm. 

This reaction has been modified to react with 2-chloroethyl dichlorophosphite and phosphorus tribromide. 

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