Org. Synth. 1951, 31, 33
DOI: 10.15227/orgsyn.031.0033
[Phosphonic acid, methyl-, diisopropyl ester]
Submitted by A. H. Ford-Moore and B. J. Perry1.
Checked by William S. Johnson and James Ackerman.
1. Procedure
A 2-l. round-bottomed flask containing 284 g. (113 ml., 2 moles) of methyl iodide2 is fitted with an efficient water-cooled condenser and a dropping funnel which is charged with 416 g. (453 ml., 2 moles) of triisopropyl phosphite (Note 1). A few pieces of porous plate are added to the methyl iodide, and about 50 ml. of the phosphite is introduced. The mixture is heated over a gauze with a free flame until an exothermic reaction begins. The flame is then withdrawn and the remainder of the phosphite is added at such a rate that the mixture keeps boiling briskly. Towards the end of the addition it may be necessary to reapply heat. After the addition is complete, the mixture is boiled under reflux for 1 hour. The condenser is replaced by a 50–75 cm. Vigreux column attached to a condenser set for distillation, and the bulk of the isopropyl iodide is distilled at 85–95° (atmospheric pressure). The residue is transferred to a pear-shaped flask for distillation through a 75-cm. Vigreux column under reduced pressure. The remainder of the isopropyl iodide is distilled at water-pump pressure, a Dry Ice trap being interposed between the receiver and the pump in order to effect complete condensation. A total of 310 g. (91%) of isopropyl iodide is thus recovered. The residue is then fractionated at vacuum-pump pressure. Except for a small fore-run and residue, the product distils almost entirely at 51°/1.0 mm. (46°/0.8 mm.). The yield of colorless product is 308–325 g. (85–90%); nD20 1.4101, nD25 1.4081; d424 0.985, d410 0.997 (Note 2).
2. Notes
1. The triisopropyl phosphite is prepared according to the procedure for triethyl phosphite (p. 955) and should be free from any diisopropyl hydrogen phosphite. The latter substance does not enter into the reaction but is difficult to remove from the final product. The starting material was supplied to the submitters by Messrs. Albright, Wilson and Company, Oldbury, Birmingham, England.
2. Diisopropyl ethylphosphonate can be obtained by a similar procedure, using the appropriate amount of ethyl iodide in place of methyl iodide. Ethyl iodide is less reactive, and it is necessary to apply heat during the addition of the phosphite and to allow the mixture to reflux for 7 hours after the addition. On a 2M scale the yield is 354 g. (91%), b.p. 61°/0.7 mm., nD25 1.4108, d425 0.968. The recovery of isopropyl iodide is 317 g. (93%).
Diethyl ethylphosphonate may be obtained by refluxing 332 g. (348 ml., 2 moles) of triethyl phosphite and 250 g. (1.6 moles) of ethyl iodide, for 3 hours. After distillation of 231 g. (92%) of ethyl iodide, the residue is fractionated under reduced pressure, giving 329 g. (98.5%) of product, b.p. 56°/1 mm. (58.5°/1.8 mm.); nD25 1.4141, nD20 1.4161; d425 1.022.
Diethyl methylphosphonate may be prepared similarly by refluxing one molar equivalent of triethyl phosphite with one mole of methyl iodide, but it is very difficult to separate the product from the small amount of diethyl ethylphosphonate that is formed simultaneously by the interaction of the phosphite with the ethyl iodide liberated in the reaction. The pure substance boils at 51°/1 mm., nD25 1.4117, d425 1.050.
3. Discussion
Diisopropyl methylphosphonate has been prepared from diisopropylethyl phosphite and methyl iodide,3 and by treating sodium diisopropylphosphonate with methyl chloride.4 The method described here for the preparation of diisopropyl methylphosphonate is a modification of the Arbusov rearrangement.5

References and Notes
  1. Chemical Defence Experimental Station, Porton, Nr. Salisbury, Wilts, England.
  2. Org. Syntheses Coll. Vol. 2, 404 (1943).
  3. Landauer and Rydon, J. Chem. Soc., 1953, 2224.
  4. Smith, U. S. pats. 2,853,507 [C. A., 53, 7989 (1959)], 2,880,224 [C. A., 53, 15978 (1959)].
  5. Arbusov, Chem. Zentr., [II] 77, 1640 (1906); Ford-Moore and Williams, J. Chem. Soc., 1947, 1465.

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

methyl chloride (74-87-3)

Methyl iodide (74-88-4)

Ethyl iodide (75-03-6)

isopropyl iodide (75-30-9)

Diisopropyl methylphosphonate,
Phosphonic acid, methyl-, diisopropyl ester (1445-75-6)

triisopropyl phosphite (116-17-6)


Triethyl phosphite (122-52-1)

diisopropyl hydrogen phosphite

Diisopropyl ethylphosphonate (1067-69-2)

Diethyl ethylphosphonate (78-38-6)

Diethyl methylphosphonate (683-08-9)

diisopropylethyl phosphite

sodium diisopropylphosphonate