Kinetics of the oxidation of phosphinic,phenylphosphinic, and phosphorous acids by N-bromoacetamide

The oxidation of phosphinic, phenylphosphinic, and phosphorous acids by N-bromoacetamide (NBA) in acid solution, results in the formation of corresponding higher oxyacids of phosphorus. The reaction is first order with respect to NBA, second order in the oxyacid and inverse first in hydrogen ions. The oxidation of deuteriated phosphorus oxyacids showed the presence of a substantial primary kinetic isotope effect. The reaction failed to induce polymerization of acrylonitrile. Added acetamide has no effect on the reaction rate. It has been shown that the ‘inactive’ tautomer of the phosphorus oxyacids, RHP(O)OH, participates in the oxidation process. A rate-determining step involving transfer of a hydride ion from the P? H bond to the oxidant has been proposed.     

无机化学中的脱水缩合反应

将无机化学中的脱水缩合反应进行分类:发生在无机含氧酸之间的脱水缩合反应;发生在无机含氧酸酸式盐之间的脱水缩合反应和酸化含氧酸盐溶液而发生的脱水缩合反应。介绍了缩合反应及缩合反应产物的应用。     

Isomerisation de la Δ5 cholestenone catalysee par quelques oxyacides phosphores

The isomerisation of Δ5 cholestenone catalysed by some oxyacids containing phosphorus has been studied. A reaction mechanism is outlined, which agrees with that already proposed using carboxylic acids, two molecules of the catalyst being involved. Phosphorous oxyacids are better catalysts than carboxylic acids. The kinetic law is complex because of the high polymerisation of these acids. The polymerisation constants are given for the first time.     

Kinetics and mechanism of the oxidation of lower oxyacids of phosphorus by hexamethylenetetramine bromine

The oxidation of lower oxyacids of phosphorus by hexamethylenetetramine bromine (HABR) in glacial acetic acid resulted in the formation of corresponding oxyacids with phosphorus in a higher oxidation state. The reaction exhibited 2:1 stoichiometry. The reaction is first order with respect to HABR. Michaelis–Menten‐type kinetics were observed with respect to the acids. The formation constant of the phenylphosphinic acid–HABR complex also has been determined spectrophotometrically. The thermodynamic parameters for the complex formation and the activation parameters for their decomposition were calculated. The reaction showed the presence of a substantial kinetic isotope effect. It is proposed that the HABR itself is the reactive oxidizing species. It has been shown that the pentacoordinated tautomer of the phosphorus oxyacid is the reactive reductant. A suitable mechanism has been proposed. © 2000 John Wiley & Sons, Inc. Int J Chem Kinet 32: 165–170, 2000     

无机化合物英文命名若干新规则的简介

依据2005年IUPAC颁布的无机物命名法,列举了同素异形体、同核多原子阳离子、同核多原子阴离子、异核多原子阴离子以及含氧酸等常见无机物的新名称,对新命名法的特点进行了分析与总结,着重介绍了加成命名法。     

Ammonia chemical ionization mass spectra of esters and amides of oxyacids of phosphorus

Chemical ionization mass spectrometry using ammonia as the reagent gas has been carried out with esters and amides of a variety of oxyacids of phosphorus (phosphates, phosphonates, phosphites and phosphoramidates). In all cases, the protonated molecular ion is a major species in the spectrum and the percentage of the total ion current carried by these protonated molecular ions is always considerably greater than that carried by the molecular ions in the corresponding electron impact mass spectra. In the chemical ionization mass spectra only limited fragmentation of the protonated molecular ion occurs from which useful information on the structure of phosphorus derivatives may be inferred.     

Complexation of citric and tartaric acids with Na and K ions in aqueous solution

The formation of MTar^–, MCit^2– and M₂Cit^– complexes (M is Na⁺ or K⁺) was established in reactions of aqueous solutions of citric and tartaric acids with sodium or potassium chloride solutions; their stability constants were determined by potentiometric titration in aqueous solution at 298.15 K and ionic strength 0.1 and 0.3 mol/l with tetraethylammonium chloride (TEACl) as a supporting electrolyte. Heat effects of reactions between citric acid solutions and sodium or potassium chlorides were measured by calorimetric method at 288.15, 298.15, and 308.15 K and at the ionic strength 0.1, 0.2, and 0.3 M TEACl. The increasing ionic strength was found to decrease exothermic effect of complex formation processes, while the temperature produced the opposite effect. Extrapolation to zero ionic strength was used to find thermodynamic stability constants and standard heat effects of complex formation reactions in solutions of oxyacids. The changes in entropy and heat capacity were calculated as well as standard enthalpies of formation of Na and K complexes of the indicated oxyacids in aqueous solution at 298.15 K.__________Translated from Koordinatsionnaya Khimiya, Vol. 31, No. 4, 2005, pp. 253–261.Original Russian Text Copyright © 2005 by Zelenina, Zelenin.     

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.     

Analytical applications of condensed phosphoric acid-IV Iodometric determination of sulphur in sulphate and sulphide ores and minerals and other compounds after reduction with sodium hypophosphite and tin metal in condensed phosphoric acid

Sulphate in sulphate ores, e.g., alunite, anglesite, barytes, chalcanthite, gypsum, manganese sulphate ore, is reduced to hydrogen sulphide by the hypophosphite-tin metal-CPA method, if a slight modification is made. Sulphide ores, e.g., galena, sphalerite, are quantitatively decomposed with CPA alone to give hydrogen sulphide. Suitable reducing agents must be used for the quantitative recovery of hydrogen sulphide from pyrite, nickel sulphide, cobalt sulphide and cadmium sulphide, or elemental sulphur is liberated. Iodide must be used in the decomposition of chalcopyrite; the copper sulphide is too stable to be decomposed by CPA alone. Molybdenite is not decomposed in CPA even if reducing agents are added. The pretreatment methods for the determination of sulphur in sulphur oxyacids and elemental sulphur have also been investigated.     

Electropolymerization of 2-aminophenylboronic acid and the use of the resulting polymer for determination of sugars and oxyacids

Electropolymerization of aminophenylboronic acids proceeds by the mechanism typical of conducting polyaniline, if the substituent in the ring is the electron donor and its position favors the electrophilic substitution into the para position with respect to the amino group in the ring. For the same reason, the polymerization of meta-aminophenylboronic acid requires the presence of fluoride ions to transform the weak electron acceptor, boronic acid group into the electron-donating trifluoroborate anion. It is shown that electropolymerization of ortho-aminophenylboronic acid can be carried out in strongly acidic media in the absence of fluoride ions, in analogy to unsubstituted polyaniline. The conductivity of the resulting polyanilineboronic acids synthesized under optimal conditions increases upon their binding with sugars and oxyacids, which allows detecting the specific interactions only, while the nonspecific interactions lower down the polymer conductivity.     

Influence of the temperature on heat effects of acid-base interactions in aqueous solutions of succinic and tartaric acids

The heat effects of interactions of solutions of succinic and tartaric acids with solutions of HNO₃ and KOH or LiOH are measured over the temperature range 288.15–308.15 K at ionic strengths of 0.5, 1.0, and 1.5 (KNO₃ or LiNO₃). The heat effects of dissociation of the acids are calculated using a Pentium-150 PC with HEAT and RRSU universal software packages. The thermodynamic characteristics of the processes of stepwise dissociation of the oxyacids are determined. The influence of the temperature on the heat effects of the processes of stepwise dissociation of succinic and tartaric acids is discussed.     

A phosphate-selective electrode based on immobilized alkaline phosphatase and glucose oxidase.

An enzyme electrode which senses oxygen consumption for the assay of phosphate ion (10^-3-10^-4M), was constructed by using two enzymes together:

The competitive inhibition by phosphate ion added caused a smaller and slower oxygen consumption which could be detected by a platinum disc electrode at -0.6 V vs. SCE amperometrically. This dual enzyme electrode was also found useful for the assay of oxyacids other than phosphate, such as arsenate, tungstate, molybdate and borate.     

THE PHOTOLYSIS OF PENICILLAMINE DISULPHIDE IN ACIDIC AQUEOUS SOLUTION

Quantum yields of penicillamine (PenSH), valine (PenH), β-hydroxyvalinc (PenOH), penicillamine trisulphide (PenSSSPen). ammonia, a keto acid and penicillamine sulphinic acid (PenSO₂H) were determined in the 254 nm-photolysis of aqueous solutions of penicillamine disulphide (PenSSPen) at pH 1.8. Oxygenation of the PenSSPen solutions prior to irradiation had no effect on the yield of PenSH, but increased the yields of PenOH, ammonia, keto acid and oxyacids of sulphur and decreased the yields of PenSSSPen and PenH. Evidence was obtained that deamination of PenSSPen is initiated by Pen. radicals in deoxygenated and PenO₂ radicals in oxygenated solutions. Flash photolysis was used to detect the PenSS. radical in irradiated PenSSPen solutions and to study its rate of decay. Comparison of the results of the investigation with those published for cystine indicate that substitution of the methylene hydrogens in cystine by methyl groups leads to a substantial increase in the importance of photochemical C-S bond fission.     

Cationic oligomerization of isoprene and structure of its oligomers

The results obtained in a study of isoprene cationic oligomerization in the presence of some oxyacids (H₂SO₄, CH₃SO₃H, Nafion^® H) are reported. Oligomers up to pentamers are obtained which were examined through gas chromatography/mass spectrometry analysis either of the reaction products or of the hydrogenated products. The structure of the dimer fraction was investigated and revealed the prevalent presence of α-pinene and p-cymene together with different cyclic unsaturated hydrocarbons. Only small quantities of linear dimers were found. Possible reaction mechanisms are presented.     

Hydrated phosphorus oxyacids alone and adsorbed on nanosilica

Low-temperature (1)Н NMR spectroscopy was used to study states of water bound to phosphoric and phosphonic acids (phosporus oxyacids, POA) alone or adsorbed onto nanosilica OX-50 (specific surface area S(BET)=52 m(2)/g) or A-300 (S(BET)=297 m(2)/g). Concentrated solutions or weakly hydrated solid POA or dried silica/POA powders placed in CCl(4) medium are characterized by different temperature dependences of the chemical shift of the proton resonance (δ(H)) because of partial dissociation of PO-H bonds strongly affected by water amounts and temperature. NMR cryoporometry results show that both small water clusters and nanodomains are present at the interfaces of hydrated solid POA and silica/POA powders. Quantum chemical calculations of the (1)H NMR spectra demonstrate the influence of POA/water cluster structure and dissociation of the PO-H bonds on the δ(H) values.     

Experimental investigation on phosphate adsorption,mechanism and desorption properties of Mn-Zn-Ti oxide trimetal alloy nanocomposite

Recently composite metal oxides have gained significant attention to be used as adsorbent because of their synergetic effects. Particularly Manganese containing composite oxides are useful for removal of inorganic oxyacids such as phosphate or arsenate. In present study fabrication of Mn-Zn-Ti Oxide adsorbent for phosphate removal carried out via co precipitation method. Surface properties deduced by TEM, FESEM, EDAX and XRD, revealed nanosized composite material has a porous nature constitute of alloy type mixing of the metals. Size of the nanocomposite found to be as small as 6?nm. Adsorption capacity for phosphate estimated at different pH, time and adsorbent dose by batch mode. In addition desorption properties and thermodynamic study also carried out. Several isotherms and kinetic models applied to observe adsorption properties of the Mn-Zn-Ti Oxide nanocomposite. Adsorption capacity found to be 151?mg/g at pH 6, time 90?min, adsorbent dose 0.20?g/L and phosphate concentration of 200?mg/L. Adsorption data fitted to second order kinetics and Freundlich isotherm. Formation of complex between nanocomposite and phosphate predicted from FTIR and supported by pH kinetic and isotherm studies. Desorption and reusability found to be well maintained over five cycles.     

The effect of supporting electrolyte on the electrochemical synthesis,morphology, and conductivity of polyaniline

Electrochemical synthesis of polyaniline (PANI) was carried out under cyclovoltammetric conditions using H₂SO₄, HCl, HNO₃, and HClO₄ as supporting electrolytes. The observed different rate of PANI deposit growth depending on the acid in the solution has been explained on the grounds of a different degree of specific adsorption for particular anion. It has been found that morphology of the deposit depends greatly upon the anion present in the solution. Thus, PANI synthesized from the solution of oxyacids results in a dense sponge-like structure while PANI from the hydrochloric acid solution results in a spaghetti-like structure. The structure of the deposit influences the conductivity, being higher for a dense deposit from oxyacid solutions and three orders of magnitude lower in case of a deposit from hydrochloric acid solution. © 1994 John Wiley & Sons, Inc.     

大自然为什么选择磷主导生命

磷酸单酯和双酯被漫长的进化过程选择为生命体的核心.磷酸酯功能的多样性需要磷酰基转移酶不断地进化来实现.现今磷酰基转移酶的催化机制已经得到了广泛研究.通过高分辨X射线晶体衍射技术(X-ray)与19FNMR的联用,来研究磷酰基转移酶的金属氟化物过渡态类似物,可以从原子层面上阐述磷酰基转移的机理.该催化机理充分地解释了磷酸酯的一对相互"矛盾"的性质,即磷酸酯结构的极其稳定性与磷酰基在信号传导过程中的灵活可调性.通过对元素周期表中其他元素的含氧酸根及其酯的性质的研究,目前还无法找出一个更加合适的元素来替代磷的这些重要功能,因而这些证据都支持了Todd的说法:"哪里有生命,哪里就一定有磷".     

Estimation of pKa for organic oxyacids using calculated atomic charges

A method for the estimation of pK_a from empirically calculated atomic charges has been developed and tested on a diverse set of organic oxyacids. The approach involves a comparison of the atomic charges calculated for both the acid and the negative ion that is formed after loss of the acidic proton. These charges have been used in conjunction with the familiar concepts of induction and resonance to develop an accurate formula to predict pK_a. Results for a set of 135 compounds, including alcohols, phenols, and carboxylic acids, yielded a fit of pK_a with r = 0.993 and an rms error of 0.455. © John Wiley & Sons, Inc.     

Partial processes during cobalt and molybdenum codeposition from solutions containing oxyacids

Distribution of citrate complexes of Co(II) and Mo(VI) in weakly acidic solutions is analyzed. It is found that the primary cathodic process is hydrogen evolution. When cathodic polarization is increased, Co(II) reduction is possible, while more negative potentials may result in full reduction of Mo(VI) to the metallic state. Reduction of H₃O⁺ ions in the solutions of oxyacids occurs with participation of a ligand playing the role of proton donor. Hydrogen evolution also remains the main electrochemical process in the molybdate solutions. It is assumed that Mo(VI) reduction occurs with participation of atomic hydrogen, but not all molybdate is reduced to metallic state. Co(II) reduction in solutions containing Mg(II) occurs to a higher extent but the degree of Mo(VI) reduction depends on the Co(II) concentration: increase in the latter results in a decrease in the content of metallic molybdenum in coatings.