Phosphonic acid hydrogenation

Phosphinic Acid. Phosphinic acid (hypophosphoms acid) is a dehquescent crystalline soHd that melts at 26.5°C. It is a monobasic acid having a piC of 2.1 and the metal salts of which generally exhibit a high solubiUty. Phosphinic acid disproportionates upon heating above 133°C to generate phosphoric and phosphonic acids, hydrogen, and phosphine. 

This reaction is catalyzed by hydrogen chloride and yields can be essentially quantitative when using either free phosphonic acid or its diesters. The flame retardant, Eyrol 6, produced by Akzo Chemicals, Inc. and used for rigid urethane foams, is synthesized as follows (24). 

Phosphonic Acid and P(III) Derivatives. Phosphonic or phosphorous acid is a white dehquescent crystalline compound having a melting point of 73.6°C. As evidenced by its stmcture,HP(=0)(0H)2, phosphonic acid is dibasic. The first hydrogen is strongly ionized, pR 1.3—1.7, and... 

This reaction can be violent partiy because of the heat Hberated in the solvation of the hydrogen chloride. The hydrolysis can be moderated by adding PCl to a saturated solution of HCI Subsequentiy, the water and hydrogen chloride are boiled until the temperature reaches 180°C. On cooling, phosphonic acid crystallizes from the melt. 

Phosphonic acid and hydrogen phosphonates are used as strong but slow-acting reducing agents. They cause precipitation of heavy metals from solutions of their salts and reduce sulfur dioxide to sulfur, and iodine to iodide in neutral or alkaline solution. 

A) The preparation of [H-chloroethoxyjchloromethyl]phosphonic acid Acetaldehyde (1.1 mol) and hydroxymethylphosphonlc acid (1 mol) in 500 ml of benzene are saturated with hydrogen chloride gas at 10°C to 15°C. The mixture is aged at 25°C for 24 hr, the solvent distilled out in vacuo and the residue flushed three times with benzene to remove all traces of hydrogen chloride. The residue is taken up in benzene (500 ml), treated with tert-butyl hypochlorite (0.8 mol) and azobisisobutyronitrile (0.8 mm) at 40°C until titration shows the absence of hypochlorite and the solution is then evaporated to yield [(1-chloro-ethoxy)chloromethyll phosphonic acid in the form of an oil. 

Hydroxyethylcellulose can be chemically modified by the reaction with vinyl phosphonic acid in the presence of the reaction product of hydrogen... 

Gonzales, L., Mo, O., Yafiez, M., Elguerdo, J., 1998b, Very Strong Hydrogen Bonds in Neutral Molecules The Phosphonic Acid Dimers , J. Chem. Phys., 109, 2685. 

Scheme 21 summarizes further reactions leading to phosphonic acid analogues of amino acids. Treatment of the nitrone (138 R =Me or Pr ) with a dialkyl hydrogen phosphonate (best as the Li derivative which shows greater diastereoselectivity than the Na or K salts), and subsequent steps involving acidolysis of the oximino compound (139) lead to the free (ot-aminoalkyl)-phosphonic acids (140)(phosphonoalanine, phosphonova1ine). 

Fundamentally, O-esters of N-hydroxy-2-thiopyridone are photo-lyzed in the presence of an excess of white phosphorus in a methylene chloride/carbon disulfide medium. On solvent removal, hydrolysis, and oxidation with hydrogen peroxide, good yields of phosphonic acids (Figure 2.10) bearing the carbon functionality of the parent acid are isolated. 

Another approach toward the preparation of analogues of natural amino acids has been reported using the salt of a phosphonous acid with an aldehyde and a substituted urea in acetyl chloride as a solvent/ facilitator.350 This approach provides analogues that bear a single acidic hydrogen at the "acid site," although the attached alkyl group at phosphorus renders the species sterically less like the natural compounds. 

Mitsubishi have reported several processes based on Ru-catalyzed hydrogenation of anhydrides and acids. Succinic anhydride can be converted into mixtures of 1,4-butane-diol and y-butyrolactone using [Ru(acac)3]/trioctylphosphine and an activator (often a phosphonic acid) [97]. Relatively high temperatures are required ( 200°C) for this reaction. The lactone can be prepared selectively under the appropriate reaction conditions, and a process has been developed for isolating the products and recycling the ruthenium catalyst [98-100]. 

The phosphonic acids, much like arsonic acid, are weak dibasic acids. In non-polar solvents, phosphonic acids associate with long chains through molecular hydrogen bonding. 

Because of the possibility of racemization during the transesterification reaction (strong basic conditions) alternative methods are reported. These include transesterification in the presence of the KF/18-crown-6 ether 461 or the use of titanium tetraalkoxides. 471 The methods are efficient and represent a route to any required dialkyl ester using diphenyl esters as starting materials. Diphenyl groups can also be removed by hydrogenation in the presence of platinum dioxide (Adams catalyst) to provide the free phosphonic acid moiety directly)46 ... 

Toluene-(4-sulfomethyl)phosphonic acid diethyl ester Hydrogen chloride Trimethylsilyl bromide Ammonium hydroxide... 

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