Kinetics and mechanism of oxidation of phosphorus oxyacids by pyridinium hydrobromide perbromide

Oxidation of three lower oxyacids of phosphorus, viz. phosphinic, phenylphosphinic and phosphorous acids by pyridinium hydrobromide perbromide (PHPB), is first-order with respect to both oxyacid and PHPB. There is no effect on addition of acylonitrile and pyridinium bromide. On oxidation, deuterated phosphinic and phosphorous acids exhibit substantial kinetic isotope effects. The effect of solvent composition on reaction rate indicates that the transition state is more polar than the reactants. Reaction rates were determined at different temperatures and the activation parameters calculated. Alternative mechanisms, involving the two tautomeric forms of the oxyacid, have been formulated and it has been concluded that the reaction proceeds through the pentacoordinated tautomer. Transfer of a hydride ion from the oxyacid to PHPB, in the rate-determining step, has been proposed.     

Thermal stability and degradation kinetics of novel organic/inorganic epoxy hybrid containing nitrogen/silicon/phosphorus by sol-gel method

Hybrids containing silicon, phosphorous and nitrogen were prepared by the sol-gel method and compared with pure epoxy. The silicon, phosphorous and nitrogen components were successfully incorporated into the networks of polymer. Thermogravimetric analysis (TGA) was used for rapid evaluation of the thermal stability of different materials. The integral procedure decomposition temperature (IPDT) has been correlated the volatile parts of polymeric materials and used for estimating the inherent thermal stability of polymeric materials. The IPDT of pure epoxy was 464 °C and the IPDTs of hybrids were higher than that of pure epoxy. The thermal stability of hybrids increased with the contents of inorganic components. The inorganic components can improve the thermal stability of pure epoxy.Two methods have been used to study the degradation of hybrids containing silicon, phosphorous and nitrogen hybrid during thermal analysis. These investigated methods are Kissenger, Ozawa's methods. The activation energies (E_a) were obtained from these methods and compared. It is found that the values of E_a for modified epoxy hybrids are higher than that of pure epoxy. The hybrids of high activation energy possess high thermal stability.     

Syntheses and Spectroscopic Study of Some New N‐4‐Fluorobenzoyl Phosphoric Triamides; Crystal Structures of 4‐F‐C6H4C(O)N(H)P(O)R2, R = NH‐C(CH3)3, NH‐CH2C6H5, N(CH3)(CH2C6H5)

Some new N‐4‐Fluorobenzoyl phosphoric triamides with formula 4‐F‐C₆H₄C(O)N(H)P(O)X₂, X = NH‐C(CH₃)₃ ( 1 ), NH‐CH₂‐CH=CH₂ ( 2 ), NH‐CH₂C₆H₅ ( 3 ), N(CH₃)(C₆H₅) ( 4 ), NH‐CH(CH₃)(C₆H₅) ( 5 ) were synthesized and characterized by ¹H, ¹³C, ³¹P NMR, IR and Mass spectroscopy and elemental analysis. The structures of compounds 1 , 3 and 4 were investigated by X‐ray crystallography. The P=O and C=O bonds in these compounds are anti. Compounds 1 and 3 form one dimensional polymeric chain produced by intra‐ and intermolecular ‐P=O···H‐N‐ hydrogen bonds. Compound 4 forms only a centrosymmetric dimer in the crystalline lattice via two equal ‐P=O···H‐N‐ hydrogen bonds. ¹H and ¹³C NMR spectra show two series of signals for the two amine groups in compound 1 . This is also observed for the two α‐methylbenzylamine groups in 5 due to the presence of chiral carbon atom in molecule. ¹³C NMR spectrum of compound 4 shows that ²J(P,C_aliphatic) coupling constant for CH₂ group is greater than for CH₃ in agreement with our previous study. Mass spectra of compounds 1 ‐ 3 (containing 4‐F‐C₆H₄C(O)N(H)P(O) moiety) indicate the fragments of amidophosphoric acid and 4‐F‐C₆H₄CN⁺ that formed in a pseudo McLafferty rearrangement pathway. Also, the fragments of aliphatic amines have high intensity in mass spectra.     

Speciation of silicon and phosphorous using liquid chromatography coupled with sector field high resolution ICP-MS

Sector-field high resolution inductively coupled plasma mass spectrometry (HR-ICP-MS) has been used, at R=3000, to resolve spectral interferences caused by N₂⁺ and CO⁺ on ²⁸Si⁺, and NOH⁺ and NO⁺ on ³¹P⁺, thereby facilitating the speciation of these elements. Polydimethylsiloxanes (PDMS), ranging from 162 g mol⁻¹ to 16 500 g mol⁻¹, and their silanol breakdown products, have been separated by size exclusion and reverse phase chromatography, respectively, and detected using HR-ICP-MS. Detection limits (as Si) of between 12–30 ng ml⁻¹ and 0.1–4 ng ml⁻¹ were obtained for the PDMS and silanol compounds, respectively. Quantitative and reproducible methods have been developed for the analysis of four common organophosphorous pesticides in blood plasma, and inorganic phosphates in food, with detection limits of between 0.9–2 ng ml⁻¹ and 1–39 ng ml^−1, respectively.     

Crystal structures of the ionic conductors Bi46M8O89 (M=P, V) related to the fluorite-type structure

The crystal structures of the two oxides Bi₄₆M₈O₈₉ (M=P, V) have been solved from single crystals X-ray data at room temperature. Bi₄₆P₈O₈₉ crystallizes in the monoclinic symmetry (space group C2/m) with the cell parameters , , and β=112.14(3)°. The symmetry of Bi₄₆V₈O₈₉ is also monoclinic but the space group is P2₁/c with the unit-cell parameters: , , and β=107.27(3)°. Both structures derive from an oxygen deficient fluorite-type structure where the Bi and M cations (M=P, V) are ordered in the framework. The structures are characterised by isolated MO₄ tetrahedra (M=P, V) which contradicts the previous results. The difference between the two structures is only due to a different order of the M atoms (M=P, V) in the fluorite-type superstructure. It will be shown that some oxygen sites are partially occupied in both structures which can explain the ion conduction properties of these phases. A structural building principle will be proposed that can explain the large domain of solid solution related to the fluorite-type observed in both systems.     

P2O5/SiO2 as an Efficient Reagent for Selective Deprotection of 1,1‐Diacetates under Solvent‐Free Conditions

A mild and efficient method has been developed for the selective deprotection of 1,1‐diacetates of aldehydes in excellent yields by means of the P₂O₅/SiO₂ reagent. Advantages of this method are the use of inexpensive and selective reagent, with high yields in simple operation, and short reaction time under solvent‐free conditions.     

SiO x -P2O5 films—promising components in photonic structure

We intend to prepare periodic multilayered structures for photonic applications. With this goal we have performed a study of some characteristics of SiO _x -P₂O₅ films deposited by the sol–gel method on glass and ITO (InSnO _x )-coated glass. The as prepared films were annealed to different temperatures (150 and 200°C). The chemical composition of the samples was determined by X-ray Photoelectron Spectroscopy (XPS). The XPS results revealed the presence of P in the as-deposited films. The structural an optical properties were examined by Fourier Transform Infrared Spectroscopy (FTIR), Spectroellipsometry (SE) and UV Transmission Spectroscopy. IR spectra of the deposited films attest the interaction of an amorphous SiO₂ with the H₃PO₄ used as a P-precursor. Refractive indices for individual SiO _x -P₂O₅ determined from SE measurements show a densification of the layer structure with the increasing temperature in the thermal treatment. The UV transmission spectra revealed a lower transmission for the sol-gel SiO _x -P₂O₅ films as compared to ITO/glass substrate. AFM images proved the densification of the films with annealing in agreement with the ellipsometric results. The work was originally presented at “Physics of Photonic Crystals and Metamaterials (PPCM)” Workshop, Brussels, 12–15 June, 2006.     

应用ICP-MS和AFS测定含磷肥料中重金属含量

肥料的投入是土壤重金属累积的重要污染来源之一,研究肥料中重金属的含量对于农产品的安全生产意义重大。为了调查我国市售含磷肥料中重金属含量状况,在部分省份农资销售点采集了159个含磷肥料样品,包括国产和进口的。应用ICP-MS和AFS分析测定了含磷肥料中Cd,Cu,Zn,Cr,Pb,Ni,As和Hg八种重金属元素的含量。结果表明,采集的含磷肥料中含有一定量的重金属元素,Cd,Cu,Zn,Cr,Pb,Ni,As和Hg的均值分别为0.77,35.6,102.7,24.1,16.6,15.4,19.4和0.08 mg·kg-1肥料。以P₂O₅为基础计算,Cd,Cu,Zn,Cr,Pb,Ni,As和Hg的均值分别为4.48,258.4,767.4,190.0,151.3,134.5,155.8和8.79 mg·kg-1 P₂O₅。所有检测样品中,只有一个磷酸一铵样品中As超标,一个进口的磷酸二铵样品中Cd超标,其余样品中重金属含量都符合肥料中砷、镉、铅、铬、汞生态指标要求(GB/T 23349-2009)。分析了13个进口肥料样品中重金属含量,重金属Cd的含量范围为0.02～27.2 mg·kg-1肥料,均值和中位值分别为3.20和0.41 mg·kg-1肥料。进口肥料中Cu,Cr和Hg高于国产肥料,均值分别为39.4,26.6和0.47 mg·kg-1肥料。     

Kinetics of Oxidation of Phosphinic, Phenylphosphinic and Phosphorous Acid by Benzyltrimethylammonium Chlorobromate

The oxidation of lower phosphorus oxyacids by benzyltrimethylammonium chlorobromate (BTMACB) proceeds by a mechanism involving a hydride-ion transfer from oxyacids to the oxidant in the rate-determining step.     

Fluorinated 1,3-diketones, 2-trifluoroacetyl phenols and their derivatives: versatile reactants in phosphorus chemistry

The role of fluorinated β-diketones, their tautomers (keto–enols) and their derivatives as reagents towards λ³P compounds is reviewed, including 2-trifluoroacetyl phenols, possessing formally a keto–enol system, and their derivatives. In an ‘insertion’ reaction phosphine and the keto–enol tautomers of 1,1,1,5,5,5-hexafluoro- and 1,1,1-trifluoropentan-2,4-dione furnished primary (S) or (R) α-hydroxy phosphines, whose enol functions probably isomerized the corresponding keto compounds. Further addition and isomerisation furnished 1,3α,5,7β-tetrakis(trifluoromethyl)-2-phospha-6-oxa-9-oxabicyclo[3.3.1]-nonan-3β,7α-diol and 1,7-trifluoromethyl-3,5-methyl-2,4,8-trioxa-6-phophaadamantane, exclusively one diastereomer in each case. The main mechanistic feature of these reactions is a consecutive diastereoselective hemiketal cyclization. 1,1,1,5,5,5-Hexafluoro- and 1,1,1-trifluoropentan-2,4-dione, as well as 2-trifluoroacetyl phenol and its imino derivatives reacted diastereospecifically with phosphonous acid dichlorides, RPCl₂ to give in a concerted mechanism thermally stable tricyclic λ⁵σ⁵P phosphoranes containing two five-membered rings and one six-membered ring. Surprisingly, the two CF₃ groups bonded to an sp³-hybridized carbon were in a cisoid arrangement having closest non-bonding FF distances of 301.4 or 273.5 pm. These findings reflect the ‘through space’ F---F coupling constants of the tricyclic phosphoranes (J_FF=4.0–7.0 Hz), in solution. 4,4,4-Trifluoro-3-hydroxy-1-phenyl-butan-1-one and methyl or phenyl phosphonous acid dichlorides gave similar tricyclic phosphoranes decomposing at ambient temperature to furnish 1,2λ⁵σ⁴-oxaphospholanes and (E)-1,1,1-trifluoro-4-phenyl-but-2-en-4-one. Dialkylphosphites and 1,1,1,5,5,5-hexafluoropentan-2,4-dione reacted to give either the (Z)-enol phosphonates or the respective γ-ketophosphonates from which in two cases four diastereomeric 2-oxo-2,5-dialkoxy-3,5-bis(trifluoromethyl)-3-hydroxy-1,2λ⁵σ⁴-oxa-phospholanes were obtained. 2-Trifluoroacetyl cyclohexanone, 4,4,4-trifluoro-3-trimethylsiloxy-1-phenylbutan-1-one, 1-benzoyl-2-trifluormethyloxirane, 1-benzoyl-2-trifluoro-methylaziridine, 2-trifluoroacetyl-1-trimethylsiloxybenzene and (trifluoroacetyl-1-phenyl) diethyl phosphate reacted with tris(trimethylsilyl) phosphite to give functionalized α-trimethylsiloxy phosphonates, which could easily be transferred into the respective phosphonic acids. In the case of an oxirane and an aziridine ketone no ring cleavage was observed. For 1,1′-(2-hydroxy-5-methyl-m-phenylene)-bis-ethanone and 1,1′-(2-trimethylsiloxy-5-methyl-m-phenylene)-bis-ethanone benzoxaphospholanes were obtained. Trialkyl phosphites and 1,1,1,5,5,5-hexafluoropentan-2,4-dione furnished cyclic phosphoranes containing the 3-hydroxy-3,5-bis(trifluoromethyl)-1,2λ⁵σ⁵-oxaphospholene structural element, stable at ambient temperature only in the case of one cyclic phosphite precursor. (E)-1,1,1-Trifluoro-4-phenyl-but-2-en-4-one and trimethylphosphite reacted to form 1,2λ⁵σ⁵-oxaphosphol-4-ene as the sole product. Results similar to the reaction of 1,1′-(2-hydroxy-5-methyl-m-phenylene)-bis-ethanone with diethyltrimethylsilylphosphite were obtained for trimethylphosphite and 2-trifluoroacetyl phenol where a deoxygenated phosphorane was found, easily hydrolyzed to give the respective phosphonic acid. With dialkylisocyanato phosphites and the keto components, 1,1,1,5,5,5-hexafluoro- and 1,1,1-trifluoropentan-2,4-dione, 4,4,4-trifluoro-1-phenyl-1,3-butandione, 2-trifluoroacetyl cyclohexanone, 2-trifluoroacetyl phenol and 1,1′-(2-hydroxy-5-methyl-m-phenylene)-bis-ethanone reacted in a ‘double’ cycloaddition to form bicyclic phosphoranes containing the 4,8-dioxa-2-aza-1λ⁵σ⁵-phosphabicyclo[3.3.0]-oct-6-en-3-one ring system; for the imino derivatives of 2-trifluoroacetyl phenol a corresponding 8-oxa-2,4-diaza- system was generated. For (E)-1,1,1,5,5,5-hexafluoro-4-trimethylsiloxy-3-penten-2-one however, a cyclic spiroimino phosphorane was obtained which underwent a [2+2] cyclodimerization to form a diazadiphosphetidine. Dimethylpropynyl phosphonite and 1,1,1,5,5,5-hexafluoropentan-2,4-dione yielded diastereoselectively a bisphosphorane, namely 1,4-bis(trifluoromethyl)-3,6-dioxa-2,2,7,7-tetramethoxy-2,7-di(1-propynyl)-2,7-diphosphabicyclo[2.2.1] heptane. When trimethylsilanyl–phosphenimidous acid bis-trimethylsilanyl–amide, Me₃SiN=PN(SiMe₃)₂, was allowed to react with 1,1,1,5,5,5-hexafluoro- and 1,1,1-trifluoropentan-2,4-dione, (E)-1,1,1,5,5,5-hexafluoro-4-trimethylsiloxy-3-penten-2-one, 2-trifluoroacetyl cyclopentanone, 2-trifluoroacetyl phenol and its imino derivatives, 2-imino-1,2λ⁵σ⁴-oxaphospholenes were found containing two diastereomers in each case, which added hexafluoroacetone across the P=N bond to give 1,3,2λ⁵σ⁵-oxazaphosphetanes.