Form Of Phosphite Research Articles

Experimental and theoretical studies on extraction of actinides and lanthanides by alicyclic H-phosphonates

Abstract Three different alicyclic substituents H-phosphonates, namely, dicyclopentyl H-phosphonate, dicyclohexyl H-phosphonate and dimenthyl H-phosphonate were synthesized and used for liquid–liquid extraction of actinide elements (U, Am and Th) and lanthanide (Gd) in n-dodecane from nitric acid medium. The physicochemical properties of the extractants, such as density, viscosity, solubility were determined. At lower acidities, these H-phosphonates exhibit higher distribution values and the extraction following cation exchange mechanism through P–OH group of tri-coordinated phosphite form. At higher acidities (2N), the extraction is primarily via solvation mechanism through P=O group of penta-coordinated phosphonate form. Amongst the three H-phosphonates, examined dimenthyl H-phosphonate showed the best results for the actinide extraction. Density functional theory (DFT) calculations were applied to understand the electronic structure of the ligands and the metal complexes. The calculated large complexation energy of UO2(NO3)2·2DMnHP is in agreement with the observed trend in experimental distribution ratio data.

Foliar Applications of Essential Nutrients on Growth and Yield of ‘Valencia’ Sweet Orange Infected with Huanglongbing

Huanglongbing (HLB) causes citrus root systems to decline, which in turn contributes to deficiencies of essential nutrients followed by decline of the canopy and yield. This study was conducted on a 6-year-old ‘Valencia’ [Citrus sinensis (L.) Osb.] on Swingle rootstock (Citrus paradisi Macf. × Poncirus trifoliata (L.) Raf.) trees in a commercial grove near Immokalee, FL, to evaluate the effects of foliar applications of selected essential nutrients (N, K, Mn, Zn, B, and Mg) on growth and productivity of citrus trees infected with Candidatus Liberibacter asiaticus (CLas), the pathogen putatively associated with HLB in Florida. Mn, Zn, B, and Mg were applied in all experiments to drip at 0×, 0.5×, 1.0×, and 2.0×/spray of what has been traditionally recommended in Florida to correct deficiencies. Treatments were applied foliarly 3×/year with the sprays occurring during each growth flush for 5 years (2010–14). Thus, the 0×, 0.5×, 1.0×, and 2.0×/spray treatments resulted in 0×, 1.5×, 3.0×, and 6.0×/year to correct deficiencies. MnS04 and ZnSO4 were applied with or without KNO3 and in separate experiments were compared with Mn3(PO3)2 and Zn3(PO3)2, respectively. Disease incidence, foliar nutrient content, canopy volume, and yield were measured. At the beginning of the experiment, foliar N, P, Ca, Mg, Cu, and B were in the sufficient range and K, Mn, Zn, and Fe were slightly low. Disease incidence was very high with 83% and 98% of trees testing positive for CLas in 2010 and 2014, respectively. Nutrients that are not mobile or have limited mobility in plants, namely Mn, Zn, and B, demonstrated an increase in foliar concentration immediately after spray and in the annual averages. Foliar K increased from the deficient to the sufficient level by KNO3 sprays, but the mobile nutrients N and Mg did not show an increase in foliar levels, indicating that intraplant transport occurs in the presence of HLB. Foliar KNO3 application had a stronger effect on growth than yield. Yield was most strongly affected by application of MnSO4 where yield of the 3×/year treatment was 45% higher than that of the unsprayed control, but yield declined by 25% for the 6×/year treatment. Yield within 95% of the maximum occurred with foliar Mn concentrations of 70–100 µg·g−1 dry weight when Mn was applied as MnSO4, which is at the high end of the traditionally recommended 25–100 µg·g−1 dry weight range. The phosphite form of Mn [Mn3(PO3)2] depressed yield by an average of 25% across all application concentrations. Zn, B, and Mg did not significantly impact yield. Canopy volume demonstrated concave relationships across application concentrations for MnSO4 and ZnSO4 without KNO3 and Mn3(PO3)2, Zn3(PO3)2, Boron, and MgSO4 with KNO3, with the minimum occurring near the 3×/year application concentration. These data indicate a complex interaction in the amount of nutrients applied and their corresponding effects on foliar concentration, growth, and yield for HLB-affected trees. The results of this study at least partially explain the current confusion among scientists and the commercial industry in how to manage nutrition of HLB-affected citrus trees. The traditionally recommended approaches to correcting nutrient deficiencies need to be reconsidered for citrus with HLB.

Mechanistic insight into the copper-catalyzed phosphorylation of terminal alkynes: a combined theoretical and experimental study.

The reaction mechanism of copper-catalyzed phosphorylation of terminal alkynes under different conditions has been investigated experimentally and theoretically. The important role of dioxygen has been elucidated, including the formation of η(1)-superoxocopper(II), η(2)-superoxocopper(III), μ-η(2):η(2)-peroxodicopper(II), and bis(μ-oxo)dicopper(III) complexes. More importantly, the proton transfer from the dialkyl phosphonate (in the form of phosphite) to the bridging oxygen atom entails the migration of the deprotonated phosphonate to the terminal alkyne, leading to the formation of a C-P bond with an activation barrier of only 1.8 kcal/mol. In addition, a particularly stable six-centered dicopper(I) species is formed with the migration of both of the Ph2P(O) groups from the copper atoms to the oxygen atoms of the bis(μ-oxo) bridge, explaining the experimental observation that secondary phosphine oxides can be oxidized to the phosphinic acids. Thus, the diphenylphosphine oxide was added to the reaction mixture dropwise to minimize the concentration during the reaction course. Gratifyingly, the coupling product was generated almost quantitatively when the reaction was completed.

RESPUESTAS BIOQUÍMICAS EN FRESA AL SUMINISTRO DE FÓSFORO EN FORMA DE FOSFITO

In this study we evaluated the concentration of total soluble sugars, chlorophylls a, b and total during blooming stage and fructification stage, and free amino acids and soluble proteins during fructification stage, in strawberry leaves cv. Festival in response to the addition of P in the form of phosphite in different proportions (0, 20, 30, 40 and 50 %) in the nutrient solution. When 20 % of total P in the form of phosphite was added in the nutrient solution, the concentrations of sugars significantly increased only during the blooming stage. Content of chlorophyll a during blooming stage did not show significant differences among treatments containing phosphite with respect to the control treatment; on the contrary, during the fructification stage, the highest content of chlorophyll a, b, and total was recorded with the addition of 30 % of P as phosphite in the nutrient solution. Total free amino acids had a concentration positively related to the proportion of total P as phosphite in the nutrient solution in the range of 0 to 30 %; higher percentages of phosphite led to a decrease in free amino acids. A similar trend in the concentration of total soluble proteins was observed; variable in which the lowest mean in the control was registered; being significantly different to the treatment involving the addition of 50 % of P in the form of phosphite. These results led to the conclusion that the addition of 30 % of total P to the nutrient solution as phosphite stimulates the accumulation of biomolecules in strawberry plants during the fructification stage.

Lightning-induced reduction of phosphorus oxidation state

Phosphorus is frequently the limiting nutrient in marine and terrestrial ecosystems. Analysis of lightning-derived glassy compounds from North America, Africa and Australia suggests that cloud-to-ground lightning increases the bioavailability of this nutrient. Phosphorus is frequently the limiting nutrient in marine and terrestrial ecosystems, largely owing to its poor solubility and slow movement through the rock cycle1,2. Phosphorus is viewed to exist in geological systems almost exclusively in its fully oxidized state as orthophosphate. However, many microorganisms use the partially oxidized forms—phosphite and hypophosphite—as alternative phosphorus sources3,4,5, and genomic evidence suggests that this selectivity is ancient6. Elucidating the processes that reduce phosphate is therefore key to understanding the biological cycling of phosphorus. Here we show that cloud-to-ground lightning reduces phosphate in lightning-derived glass compounds, termed fulgurites. We analysed the phosphorus chemistry of ten fulgurites retrieved from North America, Africa and Australia, using microprobes and 31P nuclear magnetic resonance. Half of the fulgurites contained reduced phosphorus, mainly in the form of phosphite. The amount and type of reduced phosphorus was dependent on the composition of the fulgurite section examined: carbon-rich sections contained around 22% reduced phosphorus in the form of iron phosphide, whereas other fulgurites contained between 37 and 68% in the form of phosphite. We suggest that lightning provides some portion of the reduced phosphorus used by microbes, and that phosphate reduction by lightning can be locally important to phosphorus biogeochemistry.

Umpolung catalysis: assessment of catalyst and substrate reactivities in acyloin type reactions

The umpolung of aldehydes and acylsilanes in acyloin type reactions is computationally studied by a sequence of model reactions (CPCM-THF B3LYP/6-31G(d)//B3LYP/6-31G(d)) with three different types of catalysts. Cyanide, a nucleophilic carbene and a phosphite form adducts, transition structures for [1,2]-H-shifts or [1,2]-SiMe 3-Brook rearrangements and generate the umpoled d 1-species. Aliphatic and aromatic aldehydes and acylsilanes (i.e., acetaldehyde, benzaldehyde, acylsilane, and benzoylsilane) show that π-conjugation slightly favors the umpolung. For aldehydes, the nucleophilic carbene, N-methylthiazol-2-ylidene, is by far the most reactive catalyst, while cyanide is slightly superior to the glycole based phosphite. For all catalysts, a dramatic decrease of activation barriers is apparent with the acylsilanes due to [1,2]-SiMe 3-Brook rearrangements, thermodynamically formations of d 1-species with strong Si–O bonds become highly favored.

Inhibition and pH Dependence of Phosphite Dehydrogenase

Phosphite dehydrogenase (PTDH) catalyzes the NAD-dependent oxidation of phosphite to phosphate, a reaction that is 15 kcal/mol exergonic. The enzyme belongs to the family of D-hydroxy acid dehydrogenases. Five other family members that were analyzed do not catalyze the oxidation of phosphite, ruling out the possibility that this is a ubiquitous activity of these proteins. PTDH does not accept any alternative substrates such as thiophosphite, hydrated aldehydes, and methylphosphinate, and potential small nucleophiles such as hydroxylamine, fluoride, methanol, and trifluoromethanol do not compete with water in the displacement of the hydride from phosphite. The pH dependence of k(cat)/K(m,phosphite) is bell-shaped with a pK(a) of 6.8 for the acidic limb and a pK(a) of 7.8 for the basic limb. The pK(a) of 6.8 is assigned to the second deprotonation of phosphite. However, whether the dianionic form of phosphite is the true substrate is not clear since a reverse protonation mechanism is also consistent with the available data. Unlike k(cat)/K(m,phosphite), k(cat) and k(cat)/K(m,NAD) are pH-independent. Sulfite is a strong inhibitor of PTDH that is competitive with respect to phosphite and uncompetitive with respect to NAD(+). Incubation of the enzyme with NAD(+) and low concentrations of sulfite results in a covalent adduct between NAD(+) and sulfite in the active site of the enzyme that binds very tightly. Fluorescent titration studies provided the apparent dissociation constants for NAD(+), NADH, sulfite, and the sulfite-NAD(+) adduct. Substrate isotope effect studies with deuterium-labeled phosphite resulted in small normal isotope effects (1.4-2.1) on both k(cat) and k(cat)/K(m,phosphite) at pH 7.25 and 8.0. Solvent isotope effects (SIEs) on k(cat) are similar in size; however, the SIE of k(cat)/K(m,phosphite) at pH 7.25 is significantly larger (4.4), whereas at pH 8.0, it is the inverse (0.6). The pH-rate profile of k(cat)/K(m,phosphite), which predicts that the observed SIEs will have a significant thermodynamic origin, can account for these effects.

ON THE NATURE OF THE NUCLEOPHILE IN THE MIXTURE OF PHOSPHITES AND AMINES

It is now commonly accepted that in the presence of strong bases (like metal alcoholates) an equilibrium between phosphite and phosphonate forms of dialkyl phosphites exists and that the phosphite form is highly reactive in the reaction with carbonyl compounds. There is a controversy on the structure of the active form of the phosphite when the addition is catalyzed by amines. We have found that aliphatic amines and dialkyl phoshites form a complex which is a reactive species. Its stoichiometry depends on the nature of the solvent.

Mixed phosphito–phosphonato rhodium(I) complexes

O,O′-3,3′-Di-tert-butyl-5,5′-dimethoxy-1,1′-biphenyl-2,2′-diyl phosphonate (HL)I was prepared by hydrolysis of (3,3′-di-tert-butyl-5,5′-dimethoxy-1,1′-biphenyl-2,2′-diyl)phosphorus chloride. Its tautomeric equilibrium with the corresponding phosphite form was completely shifted toward the phosphonate form. The reaction of I with the solvato complex [Rh(C8H12)(thf)2]ClO4(C8H12= cycloocta-1,5-diene, thf = tetrahydrofuran), in thf, in the molar ratio 2 : 1, afforded the rhodium(I) complex [Rh(HL)L(C8H12)] containing I co-ordinated both as a phosphonate and phosphite ligand. Carbon monoxide replaces the C8H12 ligand of 1 to afford the corresponding dicarbonyl species 2. The latter was better obtained by treating [Rh(acac)(CO)2](acac = acetylacetonate) with I, in benzene solution, in the molar ratio 1 : 2. The 31P-{1H} NMR spectra indicate for 1 and 2 the existence either of a P–OH to PO proton-exchange process faster than the NMR time-scale or of a symmetrical O ⋯ H ⋯ O bridge. The existence of a symmetrical O ⋯ H ⋯ O bridge was confirmed by treating 2 with BF3·Et2O. The acidic character of the hydrogen of the O ⋯ H ⋯ O framework was also confirmed treating 2 with NaOH. The reaction of the resulting anionic species with the solvato species [Rh(C8H12)(thf)2]ClO4 afforded a binuclear dirhodium(I) zwitterionic compound [Rh2L2(C8H12)2] containing bridging phosphonate ligands both bonded to a rhodium(I) centre through the phosphorus atoms and to the other one through the oxygen atoms. Attempts to crystallize 1 from a dilute diethyl ether–dichloromethane (4 : 1) solution also afforded the binuclear complex in low yield. Its crystal structure has been determined by single-crystal X-ray diffraction. Under catalytic hydroformylation conditions, the complexes lose the phosphorus-containing moieties to give the catalyst [RhH(CO)4].

Low-spin, five-co-ordinate, π-acid complexes of iron(II) porphyrins

The ligands, benzyl isocyanide, tri-n-butylphosphine, and triethyl phosphite form five-co-ordinate adducts with FeII(Cap), which are shown to be lowspin (S= 0).

ChemInform Abstract: REACTION OF TRIMETHYL PHOSPHITE WITH BENZALACETOPHENONE AND BENZAL‐α‐TETRALONE

AbstractBenzal‐acetophenon (I) bildet mit" Trimethylphosphit (II) bei 50°C während 50 Stdn. das Phosphoran (III), das sich in Äther mit wenig Wasser zum Keto‐phosphonat (IV) verseifen läßt. Wird die Umsetzung von (I) mit (II) in Essigsäure durchgeführt, so kann (IV) in einem einzigen Reaktionsgang erhalten werden.

Reaction of trimethyl phosphite with benzalacetophenone and benzal-α-tetralone

Benzalacetophenone and benzal-α-tetralone when heated (50–60o) for a long time with trimethyl phosphite form 1,2-oxa-4-phospholenes, which represent heat unstable compounds of pentacoordinated phosphorus.

N.m.r. Study of the Exchange of Phosphorus Bonded Hydrogen in Dimethyl- and Diethylphosphonate, Catalyzed by Acetate Ion

The exchange of the phosphorus-bonded hydrogen with deuterium in D/sub 2/ O solutions of sodium acetate was studied for dimethyl- and diethylphosphonate using a nuclear magnetic resonance technique. The exchange was found to be linearly dependent on the acetate ion concentration. From a comparison of the data obtained with those found for the oxidation of the same compounds, it is suggested that the phosphite form of the dialkyl phosphonate serves as a common intermediate for both the exchange and oxidation reactions. The substitution of deuterium for the phosphorus bonded hydrogen in diethylphosphonate had a negligible effect on the oxidation rate. This resuIt is discussed in terms of possible mechanisms for the formation of the phosphite form. (auth)

Phosphorous acid derivatives containing a cyclohexyl radical

1. Reliable methods for the preparation of dicyclohexylphosphorous acid, of dicyclohexyl phosphorochloridite, and of tricyclohexyl phosphite have been found. 2. The following mixed esters, of phosphorous acid have been prepared: methyl, ethyl, butyl, and benzyl dicyclohexyl; and cyclohexyl o-phenylene. 3. Methyl, ethyl, butyl, and benzyl dicyclohexyl phosphites, react with cuprous halides, farming viscous liquids that do,not crystallize. 4. Tricyclohexyl phosphite and cyclohexyl o-phenylene phosphite form well crystallizing complex compounds with cuprous bromide. 5. Methyl, ethyl, butyl, and benzyl dicyclohexyl phosphites behave in a peculiar fashion in the isomerization reaction with the corresponding: alkyl halides at 200–220°, cyclohexane and the corresponding alkylphosphonic acids being formed.