Alkylphosphinic acids

In the example shown in Fig. 7.6, using an alkylphosphoric acid, about 60 stages are required to give a Co/Ni ratio of about 100. So many stages would be too many for mixer-settler operation, and other types of contactors would have to be considered. In this particular example, a sieve plate pulsed column has been shown to be very effective [3]. Flowever, with the development of the alkylphosphonic and alkylphosphinic acids, the separation of cobalt and nickel can be achieved in very few stages, owing to the high rejection of nickel (see Chapter 11). 

Alkylphosphinic acids should also be considered as compounds in which the alkyl is directly attached to phosphorus, since they have been obtained by the oxidation of primary alkylphosphines with fuming nitric acid. (CH3)2=PO-OH is hardly an acid, but rather resembles a higher aliphatic alcohol in its waxy appearance and melting-point (76° C.). This compound sublimes without decomposition. 

A large number of Mannich reactions leading to P-aminomethyl derivatives involves hydrolytic steps in the proeess, the resulting products being mainly the amino-methyl phosphonie or aminomethyl alkylphosphinic acid derivatives 174 and 175 (Fig. 61). 

R2POH [R2P(0)H] Phosphinous acid (alkylphosphinous acid esters alkyl dialkylphosphinite) phosphinige Satire... 

Disproportionation of alkylphosphinic acid or alkylphosphinates yields primary phosphines. 

Phosphorus has been determined40 in phosphosilico organic compounds (POSi bonds) by dissolving the sample in water, leaving for 4-5 h to hydrolyse (or for 30-40 min at 80°) and titrating the alkylphosphinic acid so produced with 0.1 M-alkali to the thymolphthalein end-point. A method has been described41 for the simultaneous determination of free phosphorus, combined phosphorus and silicon in the reaction products of tetraalkoxysilanes with phosphorus halides. 

Bis(trimethylsilyl) phosphonite. The reaction with ammonium phosphinate gives (MejSiO)2PH, which is reactive toward unactivated alkyl halides and imines. Accordingly, alkylphosphinic acids and a-aminophosphinic acids are more readily accessible. ... 

The following alkylphosphinous acids of the general formula RP(0H)2 are obtained by the action of water on the corresponding alkyldichlorophosphines. They are colourless syrups, solidifying below 0° C., moderately soluble in water. They are monobasic and are some-... 

The corresponding alkylphosphinous acids are oxidised by nitric acid. 

The reaction between chromium trichloride, alkylphosphinic acid, and perfluoro-alkanecarboxylate gives a series of polymers [Cr(0HX0PR R 0) 02C-(CF2) -CF(CF3)2 ]b. Similar polymers in which the proportion of OH groups was less than one per unit are more tractable, but less stable thermally. ... 

The synthesis of phosphinic peptides by a reverse sequence of P-C bond formation events (N+PC approach) is a less frequently applied strategy which may offer important diversification possibilities. In particular, an amidoalkylation condensation reaction between amides, aldehydes, and alkylphosphinic acids (the three-component Kabachnik-Fields reaction) affords in a single step the main pseudopeptidic backbone, thus facilitating fast screening of the nature of Pi position. In 1996, Chen and Coward observed that a mixture of benzyl carbamates, aldehydes, and alkylphosphinic acid 23 in AcCl can lead to Cbz-protected phosphinic pseudodipeptides 24 (Scheme 10a) [53]. This method was adjusted by Matziari et al. to the synthesis of Fmoc-protected phosphinic building blocks 25 and peptides thereof (Scheme 10b) [54]. 

As has already been mentioned in the discussion of metallic salts of organic and inorganic acids, the acid radicals of such stabilizers can represent esters of phosphoric or alkylphosphinic acids. In addition to salts of alkylphosphinic acids, the use of sodium, aluminum, barium, and calcium salts of aliphatic esters of phosphoric acid is recommended [291]. 

In order to obtain more powerful PDHc El inhibitors with effective herbicidal activity, all substituents R, R, R, R, and Yn in structure I were systemically modified. Through structural modification or optimization, more than thirty novel series of structure I including alkylphosphonates, monosalts of alkylphosphonic acids, alkylphosphinates, monosalts of alkylphosphinic acid, cycUc phosphate, and caged bicyclic phosphates were designed and synthesized (Scheme 1.20). Their herbicidal activities were evaluated. Structure-activity relationship was then established and analyzed. Enzyme inhibition, toxicities and usage of representative compounds in this group were also stodied later. 

Comparing sodium salts of alkylphosphinic acids IIIH with their corresponding phosphinates HIG, it was found that inhibitory activity against the growth of plant could be greatly enhanced when MeO attached to phosphorus in phosphinates HIG was replaced by NaO. The results of study on IIIH are described in Chap. 4. 

Scheme 1.30 Design of sodium salts of alkylphosphinic acids IIIH by modification of IIIA-IIIG...

Sodium Salts of Alkylphosphinic Acids IIIH 4.2.1 Introduction... 

As seen from Table 4.22, all of sodium salts of alkylphosphinic acids IIIH showed moderate to good herbicidal activity against the root of barnyard grass and rape at 100 and 10 mg/L. Especially, IIIH-I (Yn=3-CF3, R =Ph), IIIH-2 ( =2,4-... 

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