Titanates addition

Usually, an electrochemical measurement was made 15 min after each titanate addition. Transition times were evaluated according to Kuwana s method, and those reported for the second wave were measured from the end of the first wave [19]. 

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. 

Simple ABO compounds in addition to BaTiO are cadmium titanate [12014-14-17, CdTiO lead titanate [12060-00-3] PbTiO potassium niobate [12030-85-2] KNbO sodium niobate [12034-09-2], NaNbO silver niobate [12309-96-5], AgNbO potassium iodate [7758-05-6], KIO bismuth ferrate [12010-42-3], BiFeO sodium tantalate, NaTaO and lead zirconate [12060-01 -4], PbZrO. The perovskite stmcture is also tolerant of a very wide range of multiple cation substitution on both A and B sites. Thus many more complex compounds have been found (16,17), eg, (K 2 i/2) 3 ... 

Numerous modifications of chromium-based catalysts have been made through the introduction of various additives, the most effective of which are titanium alkoxides (38,39). These additives apparentiy reduce surface silyl chromate moieties to chromium titanates, which are then oxidized to titanyl chromates. These catalysts offer a better control of the resin molecular weight (39). 

Other. Insoluble alkaline-earth metal and heavy metal stannates are prepared by the metathetic reaction of a soluble salt of the metal with a soluble alkah—metal stannate. They are used as additives to ceramic dielectric bodies (32). The use of bismuth stannate [12777-45-6] Bi2(Sn02)3 5H20, with barium titanate produces a ceramic capacitor body of uniform dielectric constant over a substantial temperature range (33). Ceramic and dielectric properties of individual stannates are given in Reference 34. Other typical commercially available stannates are barium stannate [12009-18-6] BaSnO calcium stannate [12013 6-6] CaSnO magnesium stannate [12032-29-0], MgSnO and strontium stannate [12143-34-9], SrSnO. ... 

The standard manufacturing method for tetraalkyl titanates, such as TYZOR TPT, or tetra- -butyi titanate, TYZOR TBT [5593-70 ] involves the addition of TiCl to an alcohol. In a series of reversible displacement reactions, the alkoxy substitution products and hydrochloric acid form as follows ... 

The reaction can be driven to the tetraalkoxide stage by addition of an amine or ammonia to scavenge the Hberated hydrochloric acid. The amine or ammonium hydrochloride that forms can be filtered from the reaction mass and the tetraalkyl titanate purified by distillation. If the reaction is mn in the starting alcohol as solvent, the chloride salts formed are in a finely divided state and difficult to filter. When the reaction is mn in the presence of an inert hydrocarbon solvent such as heptane or toluene, a much more readily filterable salt is obtained. The solution of cmde tetraalkyl titanate can be distilled to remove solvent and give a pure product (1,2). 

Organic-solvent-soluble, higher molecular weight polytitanoxanes, having a proposed mdder-shaped stmcture, can be prepared by careful addition of an alcohol solution of 1.0—1.7 moles of water per mole of tetraalkyl titanate, followed by distillation of the low boiling alcohol components. Polytitanoxanes having molecular weights up to 20,000 have been prepared by this method (31). 

The 1 1 molar addition products of a primary diol and a tetraaLkyl titanate, Ti(OGO)(OR)2 may react with water to give either Ti(OGO)(OH)2 or condensed products (Ti(OGO)O), which can be used as esterification catalysts (64). 

The addition of an a-hydroxycarboxyhc acid to a tetraethylene, propylene, diethjiene, or hexylene glycol titanate gives water-soluble complexes suitable for gelling aqueous solutions of hydroxyl polymers, such as poly(vinyl alcohol) (PVA), or cellulose (qv) derivatives. These are useful as binding agents for glass fibers, clays (qv), and paper coatings (85). 

The TYZOR AA, which is a 75% isopropyl alcohol solution, is unstable in cold storage. The titanate complex precipitates from solution and causes handling difficulties. The addition of small amounts (0.05—0.15 mol water/mol titanate) of water gives a solution, TYZOR AA75, that is stable in cold-temperature storage (95). 

These mixed phosphate ester titanium complexes or their amine salts are useful as fuel additives to help maintain cleanliness of carburetors and inhibit surface corrosion. Chloride-free mixed alcohol phosphate esters can be obtained if a tetraalkyl titanate is used (101). 

Addition of one mole of P,P -dipheny1methy1enediphosphinic acid to tetraisopropyl titanate gives a chelated product, the solutions of which can be used as a primer coat for metals to enhance the adhesion of topcoats, eg, alkyds, polyalkyl acylates, and other polymeric surface coating products, and improve the corrosion resistance of the metal to salt water (102). 

The alkoxy titanate compounds formed by reaction of one mole of tetraalkyl titanate with one mole of a dialkanolamine are excellent esterification catalysts for the manufacture of phthalate-based plasticizers (112). If a 1 1 molar mixture of alkanolamine and water is used ia place of the alkanolamine, oligomeric titanate complexes are formed, which have high catalyst activity and can be used as thixotropic additives to paints and other aqueous coating formulations (113). 

These polyol-stabilized alkan olamine titanate solutions are used ia a method to improve the wet strength of paper (115,118). The addition of 1—2... 

Similarly, the stabiUty of aqueous solutions of monoacetjlacetone or monotriethanolamine titanate complexes can be improved by the addition of glycol ethers (120). These solutions are useful ia appHcations ia which the catalytic, cross-linking, or film-forming actions of titanates are desired to take place ia aqueous systems. 

The addition of an alkanolamine, such as diethanolamine, to TYZOR TBT, as well as the use of a less moisture-sensitive alkanolamine titanate complex such as TYZOR TE, has been reported to prolong catalyst life and minimi2e ha2e formation in the polymer (475—476). Several excellent papers are available that discuss the kinetics and mechanism of titanate-cataly2ed esterification and polycondensation reactions (477—484). 

MetlylEsters. The addition product of two moles of TYZOR TPT and one mole of ethylene glycol, GLY—TI, can be used as a transesterification catalyst for the preparation of methyl esters. The low solubility of tetramethyl titanate has prevented the use of them as a catalyst for methyl ester preparation (488). 

Mixtures of a titanium complex of saturated diols, such as TYZOR OGT, and a titanium acylate, such as bis- -butyl-bis-caproic acid titanate, do not have a yellowing or discoloring effect on white inks used to print polyolefin surfaces (506). The complexes formed by the reaction of one or two moles of diethyl citrate with TYZOR TPT have an insignificant color on their own and do not generate color with phenol-based antioxidants (507). The complexes formed by the addition of a mixture of mono- and dialkyl phosphate esters to TYZOR TBT are also low color-generating, adhesion-promoting additives for use in printing polyolefin films (508). 

The addition of one mole of a diol, such as ethylene glycol, 1,2-propanediol, or 1,4-butanediol, to bis-acetylacetone titanate complexes gives a complex that is stable on dilution with water and that can be used in aqueous printing inks (509). An excellent review of the use of organic titanates in printing inks is available (510). 

Barium titanate is usually produced by the soHd-state reaction of barium carbonate and titanium dioxide. Dielectric and pie2oelectric properties of BaTiO can be affected by stoichiometry, micro stmcture, and additive ions that can enter into soHd solution. In the perovskite lattice, substitutions of Pb ", Sr ", Ca ", and Cd " can be made for part of the barium ions, maintaining the ferroelectric characteristics. Similarly, the TP" ion can partially be replaced with Sn +, Zr +, Ce +, and Th +. The possibihties for forming solution alloys in all these stmctures offer a range of compositions, which present a... 

Historically, materials based on doped barium titanate were used to achieve dielectric constants as high as 2,000 to 10,000. The high dielectric constants result from ionic polarization and the stress enhancement of k associated with the fine-grain size of the material. The specific dielectric properties are obtained through compositional modifications, ie, the inclusion of various additives at different doping levels. For example, additions of strontium titanate to barium titanate shift the Curie point, the temperature at which the ferroelectric to paraelectric phase transition occurs and the maximum dielectric constant is typically observed, to lower temperature as shown in Figure 1 (2). 

Strontium titanate [12060-59-2] SrTiO, becomes an n-ty e semiconductor when additional electrons are created on the Ti lattice sites by donor doping or when oxygen is removed from the material through heat treatment in a reducing atmosphere. The mobiUty of the electrons in the conduction band is about 6 crc] j(V-s). On the other hand, when ZnO is reduced, 2inc interstitials are formed and these act as donors, each yielding a free electron. 

CWorine is an elemental ehemieal tliat exists as a gas at ambient eonditions but liquefies at moderate pressures. Some of its eommon pliysieal properties are listed in Table 8.1.1. Chlorine is sliglitly water soluble, is yellow-green in the gaseous state, and lias a strong eliaraeteristie odor. Because ehlorine gas is about 2.5 times denser titan air, it tends to stay elose to the ground when released into tlie atmosphere. Liquid ehlorine lias a elear amber color one volume of liquid ean vaporize to about 460 volumes of gas. In addition, liquid elilorine has a large eoeffieient of thermal expansion. 

The reader should note tliat since many risk assessments have been conducted on the basis of fatal effects, there are also uncertainties on precisely what constitutes a fatal dose of thennal radiation, blast effect, or a toxic chemical. Where it is desired to estimate injuries as well as fatalities, tlie consequence calculation can be repeated using lower intensities of exposure leading to injury rather titan dcatli. In addition, if the adverse healtli effect (e.g. associated with a chemical release) is delayed, the cause may not be obvious. Tliis applies to both chronic and acute emissions and exposures. 

Enhanced anti-corrosion properties are also reportedly achieved by mill additions of lithium titanate, lithium aluminate or magnesium titanate to the host glass frit . 

Allylic titanates having an electrofugal leaving group, e.g., trimethylsilyl68 75 - 77, at the 3-position are powerful reagents for the highly stereoselective synthesis of 1-hetero-substituted 3-alkadienes. For the carbonyl addition of the appropriate titanated allyl sulfides ( ) or carbamates ( and ), reliable y-selectivity and anti diastereoselectivity are reported. The... 

The addition of titanated 2-methylpropenamides to 2-(ter/-butoxycarbonylamino)a]dehydes was investigated during the synthesis of dipeptide isosteres and was shown to exhibit low selectivity only93,94. 

The addition of titanated allyl carbamates to jV-protectcd (S )-amino aldehydes allows rapid access to intermediates for various dipeptide isosteres98-10°, offering a versatile brick-box system (Table 5). If an acidic amino group is present, two equivalents of reagent are required. 

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