Titanium tetraethoxide

Stmctures are highly varied among the transition metals. The titanium atom in titanium tetraethoxide has the coordination number 6 (Fig. 1). The corresponding zirconium compound, with coordination number 8, has a different stmcture (Fig. 2). Metal alkoxides are colored when the corresponding metal ions are colored, otherwise they are not. 

Under an atmosphere of dry nitrogen, titanium tetraethoxide (2.4 g, 10.4 mmol) in 10 ml of dry toluene was added over 10 min to 2-methyl-6-hydroxybenzothiazole (1.72 g, 10.4 mmol) in 40 ml of dry toluene. When the addition was complete, the reaction mixture was boiled for 15 min and then slowly distilled to remove the ethanol. A total of 20 ml of solvent was collected. The reaction mixture was allowed to cool to room temperature and P-phenylcinna-maldehyde (2.17 g, 10.4 mmol) in 50 ml of dry toluene was added dropwise to it. When the addition was complete, the reaction mixture was refluxed for 2 to 5 h, allowed to cool, and poured onto 100 ml of dilute aqueous ammonium chloride solution. The organic layer was separated, dried over anhydrous magnesium sulfate, and the solvent removed on a rotary evaporator. The residue was chromatographed on silica using 40% diethyl ether in pentane as eluent. The photochromic fractions were combined, the solvent removed, and the crystalline residue recrystallized from a heptane-benzene mixture. The product (1.6 g, 44%) had a melting point of 215°C. 

Since the first synthesis of Ti-MCM-41, several Ti-containing mesoporous molecular sieves, such as Ti-HMS, Ti-MCM-48, Ti-MSU-1, and Ti-SBA-15 have been synthesized and characterized. In most instances the syntheses were accomplished using organic precursors, namely, TEOS and titanium tetraethoxide (TEOT) or titanium tetrabutoxide (TBOT) as the Si and Ti sources, respectively. It is easy to form a homogeneous gel using organic precursors. 

Although N sulfinyl imines can be prepared by several other methods (oxidation of sulfenimines [12] and iminolysis of sulfinates [13]), they are most conveniently synthesized by condensing aldehydes with tert butanesulfinamide in the presence of copper(II) sulfate or magnesium sulfate/pyridinium p toluenesulfonate as a Lewis add catalyst and water scavenger (Scheme 1.4) [14]. When ketones, more sterically hindered aldehydes or even electronically deactivated aldehydes are used, titanium tetraethoxide is the preferred Lewis add and water scavenger. These methods are convenient to synthesize both alkyl and aryl substituted imines. 

Barringer, E.A. and Bowen, H.K., High-purity, monodisperse TiOj powders by hydrolysis of titanium tetraethoxide. 2. Aqueous interfaciai electrochemistry and dispersion stability, Langmuir, 1, 420, 1985. 

Although strictly outside the reactions of prenyiphenolic compounds the extensive work on the regiospecific general synthesis of chrom-3-enes (2H-benzo[b]pyrans), in particular2,2-dimethylchromenes, from the reaction of metal phenoxides with 3-methylbut-3-enal is very noteworthy. In the general procedure a solution of titanium tetraethoxide (0.025 mol) in toluene was treated with the phenol (0.1 mol) in toluene and the ethanol formed removed by distillation over... 

Ti-MCM-48 samples were synthesised using amorphous silica, (Aerosil 200, Degussa) as silicon source, titanium tetraethoxide (Alpha Products), cetyltrimethylammonium bromide... 

E, A, Barringer and H, K, Bowen, High-purity, monodisperse Ti02 powders by hydrolysis of titanium tetraethoxide, , synthesis and physical-properties, Langmuir, 1 414 20, 1985 J, H, Jean and T, A, Ring, Nucleation and growth of monosized TiOi powders from alcohol solution, Langmuir, 2 251-255,1986... 

Abbreviations. AITSB, aluminum tri-sec butoxide TTIP, titanium tetraisopropoxide TTE, titanium tetraethoxide EtjO, diethyl ether MgChe, magnesium chelate MgAc, magnesium acetate aq.surf, aqueous solution of surfactant. 

According the method of Stober et al. [1] colloids with a narrow size distribution are prepared via ammonium hydroxide-catalyzed hydrolysis and condensation of tetraalkoxysilanes and titanium tetraethoxide. The particle size can also be adjusted by variation of several reaction parameters (monomer, NH3 and H2O concentration solvent temperature) and by controlled cocondensation. The last method enables the incorporation of chromophores in two different ways ... 

In the fabrication route used by Barringer and Bowen (89), powders with controlled characteristics are prepared and consolidated, by colloidal methods, into uniformly packed green bodies (e.g., similar to that shown in Fig. 1.17). An abbreviated flow diagram of the fabrication route is shown in Fig. 1.27b. Powders are prepared by controlled hydrolysis of titanium tetraisopropoxide (denoted powder I) or titanium tetraethoxide (powder II). The powder particles are nearly spherical and almost monosized. After washing, each powder is dispersed in a basic aqueous solution to produce a stable suspension. Consolidation of the suspension is accomplished by gravitational or centrifugal settling. The consolidated body is dried in a vacuum and sintered for —90 min at 800°C (for powder... 

As an example, consider the SiOi-TiOi system, for which the starting materials are commonly TEOS and titanium tetraethoxide Ti(OEt)4. The hydrolysis rate of TEOS, we recall, is much slower than that for the titanium ethoxide. If the TEOS is diluted with ethanol (e.g., 1 mol of ethanol to 1 mol of TEOS) and partial hydrolysis of the solution is carried out with the addition of 1 mol of water per mole of TEOS, the majority of the silanol species will contain one OH group ... 

Titanium tetraethoxide was first obtained pure by Bischoff and Adkins by the reaction of sodium ethoxide with titanium tetrachloride (Eq. 2.53). 

On the basis of the boiling points measured for various normal alkoxides at different pressures, Cullinane et al observed that the results do not conform to the relation, ogp = a — b/T (p is the pressure in mm at which boiling point T was observed and a and b are constants). However, the latent heats and entropies of vaporization and the Trouton constants indicate that titanium tetraethoxide exhibits anomalous behaviour, i.e. it shows a distinctly higher Trouton constant (42.5) than those observed for n-propoxide, n-butoxide, n-amyloxide, and n-hexyloxide (29.1, 35.6, 39.4, and 40.5, respectively). 

This type of facile reactivity was first observed in 1936 by Jennings eia/. who synthesized titanium monochloride triethoxide and dichloride diethoxide by the reactions of titanium tetraethoxide and acetyl chloride in the appropriate molar ratios. 

TiCl4 in oxygen [11], hydrolysis of titanium alkoxides in different conditions [12], photo-assisted sol-gel method from titanium tetrabutoxide [13], hydrothermal oxidation of metallic titanium powder [14], hydrothermal hydrolysis of titanium tetraethoxide [15], oxysulfate [16,17] and tetrabutylammonium [18], solvothermal synthesis from titanium butoxide in 2-butanol [19], crystallization of amorphous Ti02 in hydrothermal condition [20], vapor hydrolysis of titanium tetraisopropox-ide [21], destabilization of titanium lactate [22], decomposition of titania-hydrate [23], epoxide sol-gel process to aerogel of Ti02 [24], hydrolysis of aqueous solution of TiCl4 in the presence of polyethyleneglycol [25], and so forth. 

Barringer E.A. and Bowen H.K. (1985) "High purity monodispersed TiC>2 powders by hydrolysis of titanium tetraethoxide" Langmuir 1, 414-20. 

Another clear illustration of the importance of particle packing is provided by studies of sintering of monospheres of titania. The spheres are made by hydrolysis of titanium tetraethoxide and, as discussed in Chapter 4, they grow by aggregation of much smaller particles. Edelson and Glaeser [91,92]... 

An example of Ellman s methodology as applied to a chiral reduction has been described in a drug discovery programme undertaken by Merck to develop selective non-steroidal glucocorticoid receptor agonists such as 243. Ketone 238 was converted to ketimine 239 by reaction with (i )-(-l-)-tert-butanesulfinamide and titanium tetraethoxide. Asymmetric reduction was effected by treatment with sodium borohydride followed by deprotection under acidic conditions to afford amine 242. The chiral product was subsequently converted to glucocorticoid receptor agonist 243 (Scheme 14.80). 

It is suggested that a part of titanium atoms on the carrier is solublized by MAO treatment in aromatic solvent. As a result, the amounts of homogeneous active site for syndiospecific polymerization increased. When the titanium compound without halogen such as titanium tetraethoxide Ti(0Et)4 was used as a catalyst, atactic or syndiotactic polystyrene were obtained and isotactic polystyrene was not obtained even if the molar ratio of A1 to Ti is low level. 

Dispersion of Ti02 in the pore systems of zeohtes has been achieved by different impregnation techniques Hashimoto et al. used titanium tetraethoxide in cyclohexane and impregnated mordenite in an autoclave at 300 °C, expecting the alkoxide to be hydrolyzed by water adsorbed on the zeohte [62]. Zhang et al. 

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