FTIR Spectroscopy,SAXS and Electrical Conductivity Studies of the Hydrolysis and Condensation of Zirconium and Titanium Alkoxides

A continuous flowing-rapid mixing technique was combined with FTIR, SAXS and electrical conductivity to study the early stages of polymer formation and growth during the acid-catalyzed hydrolysis and condensation of titanium and zirconium alkoxides. Reaction times as short as 80 milliseconds were investigated. FTIR spectroscopy was used to monitor the water and M−OR concentrations during the reaction. Hydrolysis of ∼25–50% of the alkoxy groups was facile. The FTIR and SAXS data showed that condensation was also very rapid. The activity and mobility of the ions in the solution were monitored by electrical conductivity measurements. The decrease in the normalized solution conductivity during the reaction correlated with the loss of [M−OR]. Furthermore, the radius of gyration of the growing polymers increased rapidly in regimes where the conductivity and [M−OR] decreased fastest. This finding suggests that the mobility of some of the charge carrying species decreases because of the growth in size of the polymers. Managed by Lockheed-Martin Energy Systems, Inc.     

Reactions of Titanium Alkoxides with N-Methylaminoalcohols

N-methylaminoalkoxides of titanium of the type Ti(OR)_4?n(O · CHR′ · CH₂ · NR″R?)_n where R = Et and Pr¹; n = 1–4; and R′ = R″ = H, R? = Me; R′ = H, R″ = R? = Me; R′ = R″ = R? = Me, synthesized by the reactions of titanium alkoxides with aminoalcohols, show interesting variations in their properties like physical state, volatility and molecular complexity. I.r. and p.m.r. spectra of these derivatives have been recorded. A few interchange reactions with methanol and tert-butanol have also been carried out. These aminoalkoxides get cleaved with acetyl chloride and undergo insertion reactions with phenylisocyanate, thus providing the first examples of insertion reactions in such derivatives.     

Polymerization Behaviour of Organically Modified Titanium Alkoxides in Solution

Modified titanium alkoxides with polymerizable organic ligands allow the synthesis of copolymers consisting of hybrid organic/inorganic networks. In this work titanium based-precursors were characterized in relation to the polymerization behaviour of the organic matrix. Alkoxide sols were prepared by reaction of methacrylic acid, itaconic acid anhydride, isoeugenol, p-vinylbezoic acid, p-vinylphenylacetic acid, and acetoxyacetomethacrylate with titanium tetraisopropoxide and titanium tetraethoxide. Polymerization reactions were carried out in solution using UV-irradiation and a redox-system of dibenzoylperoxide/N, N-dimethyl-p-toluidine as radical initiators. Especially for chemical activation some complexes showed high reactivity similar to silica-based methacrylates. The systems investigated are capable of acting as adhesive promoters between metal and polymer in dental applications.     

Vanadium-Catalyzed Condensation of Ethyl Cyanoacetate with Ketones

Vanadium compounds and complexes activated by pyridine or morpholine catalyze condensation of ethyl cyanoacetate with ketones and aldehydes leading to alkylidenecyanoacetates in 75–100% yield.     

Ultrasonic Agitation in Basic Alumina Catalyzed Aldol Condensation of Ketones

The use of ultrasonic irradiation to improve the yield and to shorten the reaction time of aldol dimerization of ketones catalyzed with basic alumina is described.     

Living Ring-Opening Polymerization of Cyclic Esters with Epoxide-Derived Titanium Alkoxides

Summary: The Ti^IIICp₂Cl-catalyzed radical ring opening of epoxides produces Ti alkoxides which initiate the ring-opening polymerization of ε-caprolactone. A linear dependence of on conversion, linear kinetics, low values, and the synthesis of block copolymers demonstrate a living process, while NMR spectroscopy confirms the presence of the initiator chain end. Epoxides are thus introduced as a new class of initiators for the Ti-catalyzed living ring-opening polymerization of cyclic esters.

The TiCp₂Cl-catalyzed radical ring opening of epoxides followed by the initiation of the living ring-opening polymerization of ε-caprolactone.     

Chlorotrimethylsilane‐Promoted Condensation of Ketones and Aminoazoles

Chlorotrimethylsilane‐promoted reaction of ketones and aminoazoles (i.e., 3‐amino‐1,2,4‐triazoles, 5‐aminotetrazole) at 2 : 1 ratio resulted in the formation of 4,5‐dihydroazolo[1,5 ‐ a]pyrimidine derivatives as the single regioisomers in 35 – 71% yields. In the case of tert‐butylmethylketone and 5‐aminotetrazole as the starting materials, the solvent (dimethylformamide) entered the reaction instead of the second ketone molecule.     

超声波作用下的钛醇盐水解法制备纳米TiO2

近十几年来, 有关二氧化钛光催化性能的研究已引起人们的浓厚兴趣, 在此方面进行了大量研究. 目前, 纳米二氧化钛的制备方法主要有化学沉淀法、溶胶-凝胶法、气相法和水热法等[1,2]. 超声化学是近年来新兴的一门边缘交叉学科, 已被应用于制备具有特殊结构和性能的纳米材料, 如金属[3]、碳化物[4]、氮化物[5]、氧化物[6]、合金[7]以及生物材料[8]等, 但对于超声作用在纳米粒子晶型转变方面的研究报道较少.     

On the Influence of Metal Alkoxides on the Epoxide Ring-Opening and Condensation Reactions of 3-Glycidoxypropyltrimethoxysilane

The extent of the epoxide ring-opening, the formation of ethyl ether groups as one reaction product of the ring-opening and the condensation degree of RSi(O_0.5)₃ units in sols and gels of the system 3-glycidoxypropyltrimethoxysilane (GPTS)-1.5H₂O-0.01/0.1/1.0 metal alkoxide [Si(OEt)₄, Sn(OBu^t)₄, Al(OBu^s)₃, Al(OEtOBu)₃, Ta(OEt)₅, Ti(OEt)₄, Zr(OBuⁿ)₄] in ethanol has been examined by means of liquid- and solid-state ₁₃C and ₂₉Si NMR spectroscopies. The results reveal a strong epoxide ring-opening effect of Al-alkoxides in hybrid sols after 24 h reaction time and of Zr-, Ta-, Al- and Sn-alkoxides in corresponding hybrid gels already at low concentration (1 mole%). The ring-opening rate increases in sols with higher metal alkoxide concentration (10 mole%) but decreases at 50 mole% concentration of Al-, Ti- and Zr-alkoxides. The ring-opening activity of metal alkoxides in 10 mole% hybrid sols increases after 24 h reaction time in the order Si(OEt)₄ < Ti(OEt)₄ < Zr(OBuⁿ)₄ < Ta(OEt)₅, Sn(OBu^t)₄, Al(OBu^s)₃, Al(OEtOBu)₃. The 24 h hybrid sols and gels contain considerable amounts (up to 90%) of ethyl ether groups as reaction product of the ring-opening reaction which lowers the formation of polyether bonds. The condensation degree (c.d.) of RSi(O_0.5)₃ units of GPTS-1.5H₂O sols with 10 mole% of metal alkoxides increases up to 80% after 7 h reaction time in the order: Si(OEt)₄ Sn(OBu^t)₄ < Zr(OBuⁿ)₄ < Al(OBu^s)₃ < Al(OEtOBu)₃ < Ta(OEt)₅ < Ti(OEt)₄. An additional increase in c.d. up to 90% follows after the thermal sol-gel transformation. Generally, maximum activity of metal alkoxides in ring-opening and condensation reactions was found in sols and gels with 10 mole% additives. The effect of water on the epoxide ring-opening and on c.d. is discussed. Furthermore, the activity of metal alkoxides is compared with corresponding nanoscaled metal oxides.     

Hydrolysis of Titanium Alkoxides: Thermochemical, Electron Microscopy, Saxs Studies

Hydrolysis of Ti(OR)₄ (R = Et, ⁱ Pr, ⁿ Bu) at various concentrations of titanium alkoxides and ratios h = [H₂O] /[Ti(OR)₄] is studied in alcoholic medium by means of calorimetry, electron microscopy, SAXS, and chemical analysis. The measured values for heat of hydrolysis of Ti(OR)₄ by excess water (– H _h ) at 298.15 K comprise 14.2, 64.9, 19.3 kJ/mol for R = Et, R = Et, ⁱ Pr, ⁿ Bu respectively. – H _h increases drastically in the region of 0h ratio. In the solid hydrolysis product with the composition TiO _x (OR)_4–2x ·y ROH, both x and y increase with increase of Ti(OR)₄ concentration in solution. Bushy network first formed in solution as a result of hydrolysis gradually structures with formation of well-shaped spherical particles with diameters 0.2m. SAXS curves analysis in the range of scattering vector values s = 0.07–4.26 nm^–1 for Ti(OBu)₄ hydrolysis products allows us to suggest their multilevel nature. Speculations on the structure of titanium oxobutoxide were made on the basis of the well-known structural data for crystalline first hydrolysis products of Ti(OEt)₄ and Ti(O ⁱ Pr)₄. It is suggested to perform hydrolysis of Ti(OBu)₄ with addition of water in two steps which allows us to decrease the rate of the solid precipitate formation, to regulate particles morphology in a wide range and to obtain well-shaped spherical species more than one micron in size. The influence of the powder size distribution on the grain growth during ceramic sintering is discussed.     

5-烃基丙二酸亚异丙酯的Mannich碱与甲基酮的缩合反应

5-烃基丙二酸亚异丙酯的Mannich碱和甲基酮在弱酸如醋酸的存在下, 合成得到缩合产物5-(3-氧代烃基)丙二酸亚异丙酯(3).     

低价钛引起的邻硝基苯甲酰胺与酮的还原成环反应

报道了TiCl₄-Sm体系引起的邻硝基苯甲酰胺与酮的反应.研究发现,邻硝基苯甲酰胺与酮还原成环生成1,2-二氢喹唑啉-4(3H)-酮.产物的结构通过元素分析、IR、¹HNMR谱和单晶X射线衍射法确定.     

Mechanochemical Reaction of Aromatic Ketones and Aldehydes in the Presence of Zn-ZnCl2

The solvent-free reactions of aromatic ketones and aldehydes in the presence of Zn-ZnCl2 were performed with the aid of high-speed vibration mill, Retsch MM200 mixer mill and Retsch RM100 mortar grinder to give pinacol coupling and reduction products in varying yields.     

水介质中无催化剂下醛酮与活泼亚甲基化合物的缩合反应

报道了水相中无催化剂下各种羰基化合物与活泼亚甲基化合物的Knoevenagel缩合反应. 芳香醛与活泼亚甲基化合物如丙二腈、氰基乙酸乙酯、氰基乙酰胺的缩合在室温下即能顺利进行, 获得了很高的收率; 而对于杂环芳醛、α,β-不饱和的醛以及脂肪醛与活泼亚甲基化合物的缩合, 需在50～65 ℃下进行, 也取得了很高的收率; 对于脂肪酮、芳香酮以及二元醛与丙二腈的缩合在75～85 ℃下也能顺利地进行, 获得中等以上的收率. 反应简单、高效而且对环境友好.     

A Microwave Promoted New Condensation Reaction of Aryl Ketones With Triethyl Ortho-Formate

Under microwave irradiation, boron trifluoride has been found to mediate a new condensation reaction of aryl ketones with triethyl orthoformate to give a series of new products (C1-C10) is described. The compounds were first reported. Their structure were determined by IR, MS, and ¹H /¹³C NMR spectra.     

Three-Component Condensation of Cyclic Enamino Ketones with Phenylglyoxal Hydrate and Ethyl Acetoacetate

Russian Journal of Organic Chemistry - Three-component condensation of cyclic enamino ketones with phenylglyoxal hydrate and ethyl acetoacetate in aqueous ethanol afforded a series of...     

环糊精介入酵母细胞催化芳香酮的不对称还原反应

以苯乙酮、苯丙酮、4'-甲基苯乙酮和4'-氯苯乙酮为底物,研究了酵母细胞催化芳香酮的不对称还原反应,分别考察了添加剂β-环糊精和羟丙基-β-环糊精对酵母细胞催化芳香酮的不对称还原反应的影响,结果表明芳环上取代基的空间效应和电子效应对转化率和对映体过量值有显著的影响.环糊精是通过提高酵母液的催化效率和对底物形成包结来影响反应结果的,其中底物芳环对位有无取代基是添加剂影响反应结果的关键因素.环糊精加入量根据底物的不同在3~20mmol/L之间较合适.