Phosphonates, alkyl

Multilayers of Diphosphates. One way to find surface reactions that may lead to the formation of SAMs is to look for reactions that result in an insoluble salt. This is the case for phosphate monolayers, based on their highly insoluble salts with tetravalent transition metal ions. In these salts, the phosphates form layer stmctures, one OH group sticking to either side. Thus, replacing the OH with an alkyl chain to form the alkyl phosphonic acid was expected to result in a bilayer stmcture with alkyl chains extending from both sides of the metal phosphate sheet (335). When zirconium (TV) is used the distance between next neighbor alkyl chains is - 0.53 nm, which forces either chain disorder or chain tilt so that VDW attractive interactions can be reestablished. 

Most common is the preparation of alkyl phosphonic acid esters (phospho-nates) 4 (Z,Z = OR) from phosphorous acid esters (phosphites) 1 (Z,Z = OR). The preparation of phosphinic acid esters (Z = R, Z = OR) from phosphonous acid esters, as well as phosphine oxides (Z,Z = R) from phosphinous acid esters is also possible. 

Important and widely used variants of the Wittig reaction are based on carbanionic organophosphorus reagents, and are known as the Wadsworth-Emmons reaction, Wittig-Horner reaction or Horner-Wadsworth-Emmons reaction. As first reported by Horner, carbanionic phosphine oxides can be used today carbanions from alkyl phosphonates 13 are most often used. The latter are easily prepared by application of the Arbuzov reaction. The reactive carbanionic species—e.g. 14 —is generated by treatment of the appropriate phosphonate with base, e.g. with sodium hydride ... 

Other cyclizations at phosphorus have been observed when certain phosphinates were used in the acid-catalyzed Mannich reaction. As observed previously with various phosphonous acid derivatives, reaction of aliphatic phosphinic acids with primary amines favored the formation of 2 1 adducts (73). Thus, glycine and other a-amino acids reacted under the typical conditions with excess formaldehyde and alkyl phosphonous acids to give the bis-phosphinylmethyl adducts 125. 

Reduction of halophosphines [34-37] or alkyl phosphonates [38] using lithium aluminum hydride is commonly employed for the preparation of alkyl or aryl substituted primary phosphines (Eqs. 1-4) ... 

FIGURE 11.14 Reductive biodegradation of alkyl phosphonates and phosphites. 

We found that dichloro diorgano silanes are suitable reagents for the synthesis of diorgano bis(0-alkyl)phosphonates. A different reactivity of both chlorine atoms of the silanes is observed in the dealkylation reaction of dialkylphosphonates in contrast to Me3SiBr [2]. 

Dialkoxydichloro silanes exhibit a higher nucleophilicity compared to the chlorosilanes described before. Diethoxysilyl-bis(0-alkyl)phosphonates of type 8 are formed in 90% yield besides 10% of disilylated phosphonates in the reaction of dialkyl phosphonates with dichlorodiethoxy silanes at 50-80°C. 

The insertion of the oxiranes into a P-O-C- bond of the mixed ester takes place in the reaction of the O-alkyl O-silyl phosphonates 3 with oxiranes in contrast to the reaction above. The formed 0-(2-siloxyethyl) O-alkyl phosphonates 11 show the typical PH-reactivity with the protected HO-group for further reactions. 

Fluorapatite is the only significant phosphorus-containing mineral in the Earth s crust and schreibersite has been found in iron meteorites. The only organic species to be found containing phosphorus in meteorites are the alkyl phosphonic acids. These are at least promising even if they do not contain the P-O-P phosphoester bond unit. 

The reason for such a behaviour of arsenic acid is that arsenic is a member of the group 5A elements in the periodic table. Phosphorus and antimony are also group 5 elements and are known to be chemically similar to arsenic. On this basis [8,9], the antimonic acids were found to be poor cassiterite collectors. The alkyl phosphonic acids were not selective collectors. The ethylphenylene phosphonic acid was found to produce similar or better results compared to /7-tolyl arsonic acid. The structural formula for phosphonic acid (Figure 21.5) is similar to that of /7-tolyl arsonic acid but arsenic was replaced with phosphoms. The styrene phosphonic acid radicals are C6H5-CH-CH and p-ethylphenylene CH3-CH2-C6H4. 

Fluorinated phosphinic and phosphonic acid derivatives Perfluoro derivatives of alkyl phosphonic acid CnF2n+1-P(0)(0H)2 and alkyl phosphinic acid CnF2n+i(CmF2m+1)-P(0)0H (n = m or n m) shown with their general structural formulae in Fig. 2.11.29(1) and (II) were examined by negative ESI- and APCI-FIA-MS. These anionic surfactant compounds contained perfluoro alkyl chains [2,22,25]. By analogy with their behaviour in the TSI-FIA-MS(—) process [25], the phosphonic acid formed [M — H] ions at m/z 399 and 499... 

Fig. 2.11.30. ESI—FIA—MS(— ) overview spectrum of a mixture of perfluoro derivatives of alkyl phosphonic acid (CnF2n+i-P(0)(OH)2) and alkyl phosphinic acid (CnF2n+i...

Of interest in this section are phosphonates (R-P(=0)(-OR )(-OR")), including bisphosphonates (R-CH(P03H2)2) and phosphonoformates ((R0-)(R 0-)P(=0)(C00R")) phosphinates (RR P(=0)(-OR")) will also be mentioned briefly. In contrast to phosphates, alkyl phosphonates are not likely to be hydrolyzed by esterases due to lower acidity, a different shape, and, in some cases, the inability to undergo pseudorotation [118]. This increases the probability of alternative cleavage pathways, in particular oxidative ones, as documented below. 

Diphenylmethane catalytic hydrogenolysis kinetics, 29 241-243 reduction mechanism, 29 267 cyclization, 30 65 dehydrocyclization, 28 318 [(Diphenylphosphino)alkyl]phosphonates, 42 479... 

Diagnostic agents classification, 36 6-7 inorganic, 36 5-6 Diagonal twist, 34 253-254 Dialkyl alkyl phosphonates, in liquid-liquid extraction, 9 29... 

Indeed, the similarity of the molecules from space and the molecules of Earth is striking. For example, several aliphatic carboxylic acids up to Cg were detected, (Knenvolden et al, 1970), as well as alkyl phosphonates (Yuen and Knenvolden, 1973 Cooper et al, 1992 Pizzarello, 1994) and also heterocyclic pyrimidines (Hayatsu et al, 1975 Stocks and Schwarz, 1982). 

Cooper, G. W., Onwo, W. M., and Cronin, J. R. (1992). Alkyl phosphonic acids and sulfonic acids in the Murchison meteorite. Geochim. cosmochim. acta, 56,... 

A mixture of benzene and methanol (19 to 1) was used for spreading the alkyl phosphonates. To minimize the influence of benzene on the film properties, the concentrations of the spreading solutions were > 1.5 X 10 3 gram per ml., and the experiments were performed at tt > 4 dynes per cm. (25). Moreover, higher proportions of methanol in the spreading solution did not alter the film properties under study for selected monolayers. For the sulfates, a mixed solvent containing water-benzene-2-propanol (1 10 10) was used because with the benzene-methanol solutions the properties of the films depended on the age of solution from which the films were prepared. Stearic and palmitic acids were spread from either hexane or the benzene-methanol solvent used for the phosphonates. Identical desorption results were obtained with the two solvents. 

Table 1 Synthesis of Diphenyl [l-(Benzyloxycarbonylamino)alkyl]phosphonates...

A soln of the diphenyl [l-(benzyloxycarbonylamino)alkyl]phosphonate 4 in 45% HBr/AcOH (150 mL per 0.1 mol) was kept at rt for 1 h. Removal of the solvent and volatile products in vacuo yielded the oily hydrobromide, which crystallized upon addition of anhyd Et20. The free amine was obtained by suspending the hydrobromide in CHC13 and shaking in a separatory funnel with an equal volume of 2M NaOH until all the solid dissolved. The CHC13 layer was separated, washed with brine, dried (MgS04), and concentrated to yield 19 in >90% yield mp (R1 = Me) 36-39°C mp (R = iPr) 60-63°C mp (R1 = iBu) 57-58 °C mp (R = Ph) 63-65 °C mp (R = Bzl) 65-67 °C. 

---