Organic Syntheses Procedure

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Org. Synth. 1966, 46, 21

DOI: 10.15227/orgsyn.046.0021

CHLOROMETHYLPHOSPHONOTHIOIC DICHLORIDE

Submitted by R. Schmutzler¹

Checked by M. D. Hurwitz and W. D. Emmons.

1. Procedure

A 500-ml. three-necked flask is provided with a mechanical stirrer, thermometer, and reflux condenser equipped with a drying tube. The flask is flushed with dry nitrogen and charged under nitrogen with 502 g. (3 moles) of chloromethylphosphonic dichloride (Note 1) and 160 g. (0.36 mole) of tetraphosphorus decasulfide (Note 2). The reaction mixture is heated under reflux with stirring for 6 hours, the liquid temperature being 180–190° (Note 3). The nearly black reaction mixture is then allowed to cool to room temperature and is distilled under reduced pressure. Material distilling between 70° (40 mm.) and 150° (20 mm.) is collected (Note 4). The yield is 364–396 g. (66–72%). There is no impurity in the material thus obtained which is detectable by gas chromatography (Note 5). The product may be redistilled if desired, although in most cases this is superfluous; b.p. 64–65° (10 mm.); n²⁵D 1.5730–1.5741 (Note 6). The P³¹ n.m.r. spectrum of the product shows a peak at −74.2 p.p.m. relative to external phosphoric acid.

2. Notes

1. Chloromethylphosphonic dichloride is used as obtained from Stauffer Chemical Co. Alternatively it may be prepared from the reaction of phosphorus trichloride with paraformaldehyde.²

2. Technical tetraphosphorus decasulfide (Stauffer Chemical Co.) is employed. The product is weighed under nitrogen protection.

3. In order to prevent contact of the boiling reaction mixture with air, nitrogen is passed through a T-tube on top of the drying tube on the reflux condenser.

4. Toward the end of the distillation a thick residue is formed, and this makes the distillation difficult. After the contents of the distillation flask are cooled to room temperature, this residue may be disposed of by careful continuous rinsing with water under a well-ventilated hood.

5. An F&M 500 Program-Temperature Unit (8 ft., 20% silicon rubber on 60–80 Super Support) was used for the VPC work: program 11°/min., flow 55 ml/min. Chloromethylphosphonothioic dichloride and chloromethylphosphonic dichloride, a potential impurity, are separated cleanly under these conditions.

6. Literature³ values are: b.p. 89° (30 mm.), n²⁵D 1.5741, d²⁵25 1.5891.

3. Discussion

Chloromethylphosphonothioic dichloride has been prepared by the reaction of chloromethylphosphonic dichloride with tetraphosphorus decasulfide³^,⁴^,⁵ or with thiophosphoryl chloride under autogenous pressure.³^,⁵

4. Merits of the Preparation

The reaction of chloromethylphosphonic dichloride with tetraphosphorus decasulfide³^,⁴^,⁵ or with thiophosphoryl chloride³ are the only methods of preparation for this compound reported. The method is applicable more generally, and the syntheses of methyl-, trichloromethyl-, ethyl-, propyl-, cyclohexyl-, phenyl-, and p-chlorophenylphosphonothioic dichloride from the corresponding phosphonic dichlorides have been reported.⁴^,⁵ Phosphinic chlorides of varying structures could also be converted to the corresponding thiono compounds by comparable procedures.⁴^,⁵ The present method is preferable to the thiophosphoryl chloride procedure³^,⁵ in that does not require working under pressure.

Chloromethylphosphonothioic dichloride is a reactive and useful intermediate in organophosphorus chemistry.³^,⁴^,⁶ Of special interest is its desulfurization by trivalent phosphorus compounds such as phenylphosphonous dichloride leading to the formation of chloromethlphosphonous dichloride.³

References and Notes

Explosives Department, E. I. duPont deNemours and Company, Wilmington, Delaware.
R. A. B. Bannard, J. R. Gilpin, G. R. Vavasour, and A. F. McKay, Can. J. Chem. 31, 976 (1953).
E. Uhing, K. Rattenbury, and A. D. F. Toy, J. Am. Chem. Soc., 83, 2299 (1961).
M. I. Kabachnik and N. N. Godovikov, Dokl. Akad. Nauk SSSR, 110, 217 (1956).
K. Rattenbury, U. S. Patent 2,993,929 (1961).
R. Schmutzler, J. Inorg. Nucl. Chem., 25, 335 (1963).

Appendix
Chemical Abstracts Nomenclature (Collective Index Number);
(Registry Number)

tetraphosphorus decasulfide

chloromethlphosphonous dichloride

nitrogen (7727-37-9)

phosphoric acid (7664-38-2)

phosphorus trichloride (7719-12-2)

phenylphosphonous dichloride (644-97-3)

Chloromethylphosphonothioic dichloride (1983-27-3)

chloromethylphosphonic dichloride (1983-26-2)

silicon (89343-06-6)

thiophosphoryl chloride (3982-91-0)

p-chlorophenylphosphonothioic dichloride

paraformaldehyde (30525-89-4)

Notes

References/EndNotes

Article Compounds

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