Preparation titanium

A modified procedure suitable for intramolecular reductive coupling is achieved using low-valence titanium prepared by reduction of titanium trichloride with a zinc-copper couple followed by the extremely slow addition of ketone to the refluxing reaction mixture (0.0003 mol over a 9-hour period by use of a motor-driven syringe pump) [S60. ... 

Highly reactive metallic titanium, prepared from TiCb and potassium, reduces enol phosphates to alkenes, permitting regioselective synthesis of dienes from a,p-unsaturated ketones. ... 

Dams, R., Malinowski, M., Geise, H. J. Reductive couplings of ketones by low-valent titanium, prepared from titanium tetrachloride and reducing agents. Bull. Soc. Chim. Belg. 1981, 90,1141-1152. 

The cleavage of carbon-oxygen bonds from alkenyl or aryl phosphates can be accomplished under reductive conditions with a low valent metal. As vinyl phosphates can be formed readily from ketones, this procedure provides a method to convert a ketone to an alkene. For example, the alkenyl phosphate 74 was prepared by trapping the enolate formed on reduction of the enone 73 and was converted into the alkene 75 (7.55). The chemistry therefore provides a method to prepare structurally specihc alkenes. Low-valent titanium (prepared for example by reduction of titanium(III) chloride with potassium metal) is a convenient alternative to lithium or sodium in liquid ammonia or an amine for the reductive cleavage of alkenyl or aryl phosphates. 

Butyl vinyl ether added to a cooled soln. of 3 eqs. low-valent titanium (prepared by addition of TiC over 9 min to THF at 0° under N2, followed by cautious treatment with 95% LiAlH4 in THF over 20 min, then stirring without cooling for 30 min) followed by a soln. of 3 eqs. fluorotrichloromethane in THF over 42 min at 0°, and after a further 30 min. poured into 10% HCl/crushed ice 2-butoxy-l-chloro-l-fluorocyclopropane. Y 57% (77% by F NMR). Fluorotrichloromethane is inexpensive and conveniently handled the reaction is mild (requiring no bases), rapid, and clean. F.e.s. W.R. Dolbier, Jr., C.R. Burkholder, Tetrahedron Letters 29, 6749-52 (1988). 

A comparison of the pore structural properties of MCM-41 containing titanium, prepared at room temperature, with those of aluminosilicate grades is presented. The influence on the structural characteristics of using different metal sources and metal content is also considered. Additionally, the stability of Al-MCM-41 and Ti-MCM-41 samples, with Si/M=30, towards prolonged exposure to pure water vapour at 298K was investigated. 

Heat treatment at 400°C of hydrous oxides of titanium prepared using titanous chloride as starting material and H2O2 as oxidizing agent does not affect the amphoteric properties of the gels nor their isoelectric points. 

Esters (eq 8) and thioesters (eq 9) can be silylmethylenated by the action of the dibromide with low-valent titanium prepared from titanium(IV) chloride and zinc. The reaction produces p-hetero-substituted vinylsilanes and was (Z) selective. ... 

Kim, HM Miyaji, F Kokubo, T Nishiguehi, S Nakamura, T. Graded surface structure of bioactive titanium prepared by chemical treatment. J. Biomed. Mater. Res., 1999, 45, 100-107. 

Beryllium is added to copper to produce an alloy with greatly increased wear resistance it is used for current-carrying springs and non-sparking safety tools. It is also used as a neutron moderator and reflector in nuclear reactors. Much magnesium is used to prepare light nieial allo>s. other uses include the extraction of titanium (p. 370) and in the removal of oxygen and sulphur from steels calcium finds a similar use. 

This occurs naturally as a white solid in various crystalline forms, in all of which six oxygen atoms surround each titanium atom. Titanium dioxide is important as a white pigment, because it is nontoxic. chemically inert and highly opaque, and can be finely ground for paint purposes it is often prepared pure by dissolving the natural form in sulphuric acid, hydrolysing to the hydrated dioxide and heating the latter to make the anhydrous form. 

Discovered by Gregor in 1791 named by Klaproth in 1795. Impure titanium was prepared by Nilson and Pettersson in 1887 however, the pure metal (99.9%) was not made until 1910 by Hunter by heating TiCk with sodium in a steel bomb. 

Reductive coupling of carbonyl compounds to yield olefins is achieved with titanium (0), which is freshly prepared by reduction of titanium(III) salts with LiAIH4 or with potassium. The removal of two carbonyl oxygen atoms is driven by T1O2 formation- Yields are often excellent even with sensitive or highly hindered olefins. (J.E. McMurry, 1974, 1976A,B). 

Fig. 7. The effect of preparation on the pore size distribution (a), titanium dispersion (b), and the activity for epoxidation of cyclohexene (c) of titania—siUca containing 10 wt % titania and calcined in air at 673 K. Sample A, low-temperature aerogel Sample B, high-temperature aerogel Sample C, aerogel.

Dialkylaminoethyl acryhc esters are readily prepared by transesterification of the corresponding dialkylaminoethanol (102,103). Catalysts include strong acids and tetraalkyl titanates for higher alkyl esters and titanates, sodium phenoxides, magnesium alkoxides, and dialkyitin oxides, as well as titanium and zirconium chelates, for the preparation of functional esters. Because of loss of catalyst activity during the reaction, incremental or continuous additions may be required to maintain an adequate reaction rate. 

Long-chain esters of pentaerythritol have been prepared by a variety of methods. The tetranonanoate is made by treatment of methyl nonanoate [7289-51-2] and pentaerythritol at elevated temperatures using sodium phenoxide alone, or titanium tetrapropoxide in xylene (12). PhenoHc esters having good antioxidant activity have been synthesized by reaction of phenols or long-chain aUphatic acids and pentaerythritol or trimethyl olpropane (13). 

Titanium trifluoride is prepared by dissolving titanium metal in hydrofluoric acid (1,2) or by passing anhydrous hydrogen fluoride over titanium trihydrate at 700°C or over heated titanium powder (3). Reaction of titanium trichloride and anhydrous hydrogen fluoride at room temperature yields a cmde product that can be purified by sublimation under high vacuum at 930—950°C. 

Titanium tetrafluoride may be prepared by the action of elemental fluorine on titanium metal at 250°C (5) or on Ti02 at 350°C. The most economical and convenient method is the action of Hquid anhydrous HF on commercially available titanium tetrachloride in Teflon or Kynar containers. Polyethylene reacts with TiCl and turns dark upon prolonged exposure. The excess of HF used is boiled off to remove residual chloride present in the intermediates. 

Titanium(lV) fluoride dihydrate [60927-06-2] TiF 2H20, crystals can be prepared by the action of aqueous HF on titanium metal. The solution is carefully evaporated to obtain the crystals. Neutral solutions when heated slowly hydroly2e and form titanium(lV) oxyfluoride [13537-16-17, TiOF2 (6). Upon dissolution in hydrogen fluoride, TiF forms hexafluorotitanic acid [17439-11-17, ll]TiF. ... 

The most promising appHcation of titanium tetrafluoride is for use in topical appHcations for prevention of dental caries (7—13). It is being evaluated and compared to NaF, MFP, and SnF2 used in these appHcations. The other use is in mixed optical haHde glass (14—16), and in the preparation of fluorotitanates (17—19). 

Zirconium i dride. Zirconium hydride [7704-99-6] ZrH2, is a britde, metaUic-gray soHd that is stable in air and water, and has a density of 5.6 g/cm. The chemical properties of ZrH2 closely resemble those of titanium hydride. Thermal decomposition in vacuum (1 mPa (7.5 x 10 //mHg)) begins at 300°C and is nearly complete at 500—700°C. It is prepared in the same manner as T1H2. 

Another important class of titanates that can be produced by hydrothermal synthesis processes are those in the lead zirconate—lead titanate (PZT) family. These piezoelectric materials are widely used in manufacture of ultrasonic transducers, sensors, and minia ture actuators. The electrical properties of these materials are derived from the formation of a homogeneous soHd solution of the oxide end members. The process consists of preparing a coprecipitated titanium—zirconium hydroxide gel. The gel reacts with lead oxide in water to form crystalline PZT particles having an average size of about 1 ]lni (Eig. 3b). A process has been developed at BatteUe (Columbus, Ohio) to the pilot-scale level (5-kg/h). 

From the time that isoprene was isolated from the pyrolysis products of natural mbber (1), scientific researchers have been attempting to reverse the process. In 1879, Bouchardat prepared a synthetic mbbery product by treating isoprene with hydrochloric acid (2). It was not until 1954—1955 that methods were found to prepare a high i i -polyisoprene which dupHcates the stmcture of natural mbber. In one method (3,4) a Ziegler-type catalyst of tri alkyl aluminum and titanium tetrachloride was used to polymerize isoprene in an air-free, moisture-free hydrocarbon solvent to an all i7j -l,4-polyisoprene. A polyisoprene with 90% 1,4-units was synthesized with lithium catalysts as early as 1949 (5). 

Although white lead was the oldest white hiding pigment ia paints, it has been totally replaced by titanium dioxide, which has better covering power and is nontoxic (see Pigments). Nevertheless, basic lead carbonate has many other uses, including as a catalyst for the preparation of polyesters from... 

Preparation and Manufacture. Magnesium chloride can be produced in large quantities from (/) camalhte or the end brines of the potash industry (see Potassium compounds) (2) magnesium hydroxide precipitated from seawater (7) by chlorination of magnesium oxide from various sources in the presence of carbon or carbonaceous materials and (4) as a by-product in the manufacture of titanium (see Titaniumand titanium alloys). 

The sol—gel technique has been used mosdy to prepare alumina membranes. Figure 18 shows a cross section of a composite alumina membrane made by sHp coating successive sols with different particle sizes onto a porous ceramic support. SiUca or titanium membranes could also be made by the same principles. Unsupported titanium dioxide membranes with pore sizes of 5 nm or less have been made by the sol—gel process (57). 

Other Metals. AH the sodium metal produced comes from electrolysis of sodium chloride melts in Downs ceUs. The ceU consists of a cylindrical steel cathode separated from the graphite anode by a perforated steel diaphragm. Lithium is also produced by electrolysis of the chloride in a process similar to that used for sodium. The other alkaH and alkaHne-earth metals can be electrowon from molten chlorides, but thermochemical reduction is preferred commercially. The rare earths can also be electrowon but only the mixture known as mischmetal is prepared in tonnage quantity by electrochemical means. In addition, beryIHum and boron are produced by electrolysis on a commercial scale in the order of a few hundred t/yr. Processes have been developed for electrowinning titanium, tantalum, and niobium from molten salts. These metals, however, are obtained as a powdery deposit which is not easily separated from the electrolyte so that further purification is required. 

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