Determination of formation constants of hydroxo and carbonate complexes of Pr(3+) in 2 M NaCl at 303 K

The hydrolysis of praseodymium III in 2 M sodium chloride at 303 K was studied. Two methods were used: pH titration followed by a computational refinement and solvent extraction in the presence of a competitive ligand. The hydrolysis constants obtained by pH titration were: logbeta(1,H)=-7.68+/-0.07, logbeta(1,2H)=-15.10+/-0.03, and beta(1,3H)=-23.80+/-0.04. The stability constants of praseodymium carbonate complexes were determined by pH titration as well and were: logbeta(1,CO(2-)(3))=5.94+/-0.08 and logbeta(1,2CO(2-)(3))=11.15+/-0.15. Praseodymium carbonate species were taken into consideration for calculating the first hydrolysis constants by the solvent extraction method and the value obtained was: logbeta(1,H)=-7.69+/-0.27. The values for logbeta(1,H) attained by both methods are the same. The species-distribution diagram was obtained from the stability constants of praseodymium carbonate complexes and hydrolysis products in the conditions of the present work.     

Hydrolysis of Titanium(IV) Sulfate Solutions under Hydrothermal Conditions

The structure and the phase, granulometric, and chemical composition of hydrated titanium dioxide obtained by hydrolysis of oxotitanium(IV) sulfate and ammonium titanium(IV) oxysulfate solutions under hydrothermal conditions (130-170°C) were studied by X-ray and chemical analyses, electron microscopy, and thermogravimetry. The effect of hydrolysis conditions on the formation of samples with globular shape of particles was studied.     

Characterization of Ti(6)O(4)(O(2)C(4)H(5))(8)(OCH(2)CH(3))(8) by electrospray time of flight mass spectrometry

A titanium oxide molecular cluster prepared by hydrolysis of titanium tetraethoxide in the presence of methacrylic acid, can be characterized by electrospray time of flight mass spectrometry (ESMS-TOF). The chemistry of such systems is not well known and ESMS is a powerful technique for studying the reactions of clusters in solution. The fingerprint of the cluster fragmentation suggests formation of Ti(x)O(y) core fragments that represent commonly observed structural constructs in bulk titanium oxide metallates. The fragmentation steps provide insight into the hydrolytic conversion of this molecular sol gel intermediate into bulk TiO(2). While MS has been applied to the study of metal alkoxide hydrolysis mechanisms, mass spectra of isolated individual titanium oxide clusters have not previously been reported.     

Characteristics of the hydrous titanium dioxide-anatase phase transformation during hydrothermal treatment in aqueous solutions

The transformations of hydrous titanium dioxide, prepared by thermal hydrolysis of titanium(IV) compounds in sulfuric acid solutions, during hydrothermal treatment (150–240°C) in water were studied. The dispersivity and the chemical compositions of the samples obtained determined depending on the synthesis conditions (the composition) of hydrous titanium dioxide and the heat treatment temperature.     

Self-assembly of double stranded dinuclear titanium(IV)-Schiff base complexes and formation of intramolecular mu-oxo bridges

The reaction of titanium isopropoxide with a Schiff base ligand containing an isobutenyl linker leads to double stranded dinuclear titanium(IV)-Schiff base complexes through self-assembly with concomitant formation of intramolecular mu-oxo bridges upon hydrolysis.     

茂钛催化剂的苯乙烯间规聚合

比较了几种庞钛化合物/甲基铝氧烷/三甲基铝均相催化剂的苯乙烯间规聚合,认为茂基三正丙氧基钛[CpTi(O－n－Pr)₃]是苯乙烯间规聚合的良好催化剂[催化效率：ω_ps·ω_Ti^-1=4×10⁴g·g^-1]．探索了催化剂浓度、单体浓度、聚合温度和时间对苯乙烯聚合的影响．聚合反应产物用佛丁酮萃取,沸丁酮不可溶级分大于95％,经¹³CNMR分析该级分为间规聚苯乙烯．     

[2+2] Cycloaddition of the Schrock titanium silylidene and acetylene

Russian Chemical Bulletin - [2+2] Cycloadduct of the titanium silylidene Cp2Ti(thf)=Si[Si3(SiMeBut 2)4] and acetylene was readily prepared, isolated, and characterized by NMR spectroscopy and...     

The effect exerted by the type of the solvent and precursor in sol-gel preparation of titanium dioxide on its electrorheological activity

The effect, which the type of the solvent, as a synthesis medium, and precursor, as a starting reagent of the synthesis, exert on the rheological properties of the hydrolysis product, titanium dioxide, has studied. Titanium alkoxides were hydrolyzed in a medium of isopropyl alcohol and ethanol. As hydrolysis precursors were chosen titanium isopropoxide and titanium butoxide.     

Hydrolysis and Condensation Processes of Titanium iso-Propoxide Modified with Catechol: An NMR Study

The hydrolysis and condensation processes of titanium iso-propoxide modified with catechol (C₆H₄(OH)₂; H₂cat) have been investigated by ¹H, ¹³C and ¹⁷O nuclear magnetic resonance spectroscopy. The hydrolysis reactions of the modified titanium iso-propoxide in the system with Ti:tetrahydrofuran (THF):H₂O = 1:20:x (x = 1, 2 and 5 in a molar ratio) are essentially completed in the initial stage (<1 h), and the condensation reactions also proceed significantly during this stage. Upon hydrolysis with H₂O/Ti = 1, the iso-propoxy groups are selectively hydrolyzed and the catecholate groups remain bound to titanium. With H₂O/Ti = 2 and 5, both the iso-propoxy and catecholate groups are hydrolyzed, and the hydrolysis of the iso-propoxy groups is relatively preferential. Approximately half the catecholate groups are stably bound to titanium, even after hydrolysis with H₂O/Ti = 5.     

Ester hydrolysis by a cyclodextrin dimer catalyst with a metallophenanthroline linking group

A novel beta-cyclodextrin dimer, 1,10-phenanthroline-2,9-dimethyl-bridged-bis(6-monoammonio-beta-cyclodextrin) (phenBisCD, L), was synthesized. Its zinc complex (ZnL) has been prepared, characterized, and applied as a new catalyst for diester hydrolysis. The formation constant (logK(ML)=9.56+/-0.01) of the complex and deprotonation constant (pK(a)=8.18+/-0.04) of the coordinated water molecule were determined by a potentiometric pH titration at (298+/-0.1) K. Hydrolytic kinetics of carboxylic acid esters were performed with bis(4-nitrophenyl) carbonate (BNPC) and 4-nitrophenyl acetate (NA) as substrates. The obtained hydrolysis rate constants showed that ZnL has a very high rate of catalysis for BNPC hydrolysis, giving a 3.89x10(4)-fold rate enhancement over uncatalyzed hydrolysis at pH 7.01, relative to only a 42-fold rate enhancement for NA hydrolysis. Moreover, the hydrolysis second-order rate constants of both BNPC and NA greatly increases with pH. Hydrolytic kinetics of a phosphate diester catalyzed by ZnL was also investigated by using bis(4-nitrophenyl) phosphate (BNPP) as the substrate. The pH dependence of the BNPP cleavage in aqueous buffer shows a sigmoidal curve with an inflection point around pH 8.11, which was nearly identical to the pK(a) value from the potentiometric titration. The k(cat) of BNPP hydrolysis promoted by ZnL was found to be 9.9x10(-4) M(-1) s(-1), which is comparatively higher than most other reported Zn(II)-based systems. The possible intermediate for the hydrolysis of BNPP, BNPC, and NA catalyzed by ZnL is proposed on the basis of kinetic and thermodynamic analysis.     

A Study of the Composition of a Solid Phase Isolated on Heating Acid Solutions of Titanium(IV) Sulfate

The mechanism of solid phase formation in hydrolysis of titanium(IV) sulfate solutions was studied at elevated temperature (boiling).     

Synthesis of nanodispersed anatase by tetrabutoxy titanium hydrolysis

Nanodispersed titanium oxyhydrate was obtained by tetrabutoxy titanium hydrolysis in the presence of a chelating agent, acetylacetone. The introduction of a chelating agent to tetrabutoxy titanium hydrolysis in a water–ethanol mixture allows one to control the hydrolysis rate. According to X-ray powder diffraction data, amorphous titanium oxyhydrate after annealing at 400°C transforms to anatase, the crystallites of which are 6.2–8.4 nm in size. Transmission electron microscopy showed that the anatase particles are close to spheres 5–9 nm in diameter. The amorphous materials were studied by differential thermal analysis, thermogravimetric analysis, and mass spectrometric analysis of released gases. The benzene adsorption by the produced materials was determined. The nitrogen adsorption isotherms of two samples were constructed, and the specific surface area of the anatase particles and the pore size were found (148.5 and 98 m²/g, and 4.4 and 4.0 nm, respectively).     

A kinetics-controlled coating method to construct 1D attapulgite @ amorphous titanium oxide nanocomposite with high electrorheological activity

A new kind of one-dimension attapulgite (APG) @ titanium oxide nanoparticles was prepared via kinetics-controlled coating method. By simply altering the ammonia content and reaction time to control the kinetics of hydrolysis and condensation of tetra-n-butyl titanate (TBOT) in ethanol/ammonia mixtures, amorphous titanium oxide nanoparticles can adhere to the APG rods firmly, and the thickness of uniform amorphous titanium oxide shells can be adjusted from 0 to 40 nm. The obtained APG@ titanium oxide nanorods were applied as a new electrorheological (ER) fluid, which showed a promising ER activity. The yield stresses of the APG@ titanium oxide nanorod (40-nm shell thickness) ER fluid under electric field was 2.1 times of the granular titanium oxide ER fluid and 4.1 times of the APG ER fluid. And, the APG@ titanium oxide nanorod ER fluid also exhibited distinctly improved suspended stability.     

Synthesis and characterization of 1,2-cyclohexanedione bis-benzoyl-hydrazone and its application to the determination of ti in minerals and rocks

The synthesis, spectroscopic characteristics and analytical applications of 1,2-cyclo-hexanedione bis-benzoylhydrazone are reported. The reaction of this new compound with titanium(IV) has been studied spectrophotomelrically. An orange 1:2 metal/ligand complex (lambda(max)= 477 nm, = 1.05 x 10(4) l.mole(-1).cm(-1)) is formed at pH 1.75-3.0 in 3:2 v v ethanol-water medium. The method is simple and selective and has been satisfactorily applied to the determination of titanium in bauxite, Portland cement, amphibolites and granites.     

Synthesis of TiC-C fiber from titanium isopropoxide treated phenolic resin fiber

Precursor fibers for titanium carbide-carbon fibers were synthesized by reacting phenolic resin fibers with titanium isopropoxide (TIP). In this system, titanium oxide gel coated fiber was prepared by hydrolyzing TIP infiltrated resin fiber. The precursor fibers obtained after the hydrolysis were converted into titanium oxide-carbon fibers (TiO₂-C fibers) by pyrolysis at 1273 K. The TiO₂-C fibers were converted into titanium carbide-carbon fibers (TiC-C fibers) by heat treatment at 1373–1973 K. The mechanisms of the conversion from TiO₂-C fibers to TiC-C fibers were characterized by TGA.     

Facile synthesis of nanoporous anatase spheres and their environmental applications

Highly nanoporous TiO(2) (anatase) spheres with an excellent ability in environmental applications have been successfully prepared via in situ hydrolysis of titanium glycolate precursor spheres.     

Design of titania porous films controlled by precursors’ viscosity for photocatalytic application

Research on Chemical Intermediates - Porous transparent films of TiO2 (anatase) were obtained by controlled hydrolysis of titanium tetraisopropoxide (sol-gel method) in the presence of a...     

Photocatalysis by titanium complexes of the reaction of ClO4 −, ions with alcohol molecules

In the photolysis of perchloric acid solutions of titanium(IV) with additions of ethanol, the formation of titanium(III) compounds was detected. Irradiated solutions ([HClO₄]=0.8 M) at 77K are characterized by an anisotropic ESR signal with parameters g ₁=1.994, g ₁=1.904, which correspond to pseudo-octahedral aqua-complexes of titanium(III). With the passage of time, the signal intensity of the titanium(III) compounds decreases, which is explained by their oxidation by ClO₄ ions. During prolonged photolysis of titanium(IV) compounds in 7 M HClO₄ with an addition of ethanol, a multicomponent signal of the paramagnetic chlorine oxide ClO₂ with parameters g _xx=2,004, a _xx(³⁷Cl)=6.0. mTl a _xx(³⁵Cl)=7,30 mTl, is recorded instead of the signal of titanium(III) compounds. Evidently ClO₂ is formed as a result of a rapid dark reaction between compounds of trivalent titanium (products of the photochemical step) and chlorate ions, which are accumulated in the solution as a result of successive photochemical and dark redox conversions of the titanium compounds, perchlorate ions, arid free radicals from the alcohol molecules. The formation of free radicals in the system was established by the ESR method after irradiation of frozen solutions.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 22, No. 6, pp. 679–686, November–December, 1986.     

Schiff碱钛配合物催化n-辛基联烯聚合

采用简便的方法, 合成了Schiff碱钛配合物Ti(Salen)2Cl2[Salen为N,N-(3,5-di-tert-butylsalicylidene)anilinato]并与Al(i-Bu)3组成二元催化体系用于n-辛基联烯的聚合. 实验结果表明, 在单体与催化剂摩尔比为100, n(Al)/n(Ti)=50, 催化剂于80 ℃陈化时间1 h后, 于80 ℃本体聚合16 h得到聚n-辛基联烯, 转化率100%, 分子量Mw=1.1×105, MWD=1.77, 1,2聚合链节单元质量分数为50%.     

A catalytic antibody programmed for torsional activation of amide bond hydrolysis

Amidase antibody 312d6, obtained against the sulfonamide hapten 4 a that mimics the transition state for hydrolysis of a distorted amide, accelerates the hydrolysis of the corresponding amides 1 a-3 a by a factor of 10(3) at pH 8. The mechanisms of both the uncatalyzed and antibody-catalyzed reactions were studied. Between pH 8 and 12 the uncatalyzed hydrolysis of N-toluoylindoles 1 a and 3 a shows a simple first-order dependence on [OH(-)], while hydrolysis of 3 a is zeroth-order in [OH(-)] below pH 8. The pH profile for hydrolysis of the corresponding tryptophan amide 2 a is more complex due to the dissociation of the zwitterion into an anion with pK(a) 9.74; hydrolysis of the zwitterionic and the anionic form of 2 a both show simple first-order dependence on [OH(-)]. Absence of (18)O exchange between H(2) (18)O/(18)OH(-) and the substrate, a normal SKIE for both 1 a (k(H)/k(D)=1.12) and 3 a (k(H)/k(D)=1.24) and the value of the Hammett constant rho for hydrolysis of p-substituted amides 3 a-e are consistent with an ester-like mechanism in which formation of the tetrahedral intermediate is rate-determining and the amine departs as anion. The 312d6-catalyzed hydrolysis of 3 a was studied between pH 7.5 and 9, and its independence of pH in this range indicates that water is the reacting nucleophile. Hydrolysis of 3 a is only partially inhibited by the sulfonamide hapten, and this indicates that non-specific catalysis by the protein accompanies the specific process. Only the nonspecific process is observed in the hydrolysis of amides 3 with para substituents other than methyl. Binding studies on the corresponding series of p-substituted sulfonamides 5 a-e confirm the high specificity of antibody 312d6 for p-methyl substituted substrates.