Titanium anhydride

Synonyms titanic oxide titanic acid anhydride titanium anhydride titania titanium white... 

The reaction uses a fixed-bed vanadium pentoxide-titanium dioxide catalyst which gives good selectivity for phthalic anhydride, providing temperature is controlled within relatively narrow limits. The reaction is carried out in the vapor phase with reactor temperatures typically in the range 380 to 400°C. 

Other Rea.ctlons, The anhydride of neopentanoic acid, neopentanoyl anhydride [1538-75-6] can be made by the reaction of neopentanoic acid with acetic anhydride (25). The reaction of neopentanoic acid with acetone using various catalysts, such as titanium dioxide (26) or 2irconium oxide (27), gives 3,3-dimethyl-2-butanone [75-97-8] commonly referred to as pinacolone. Other routes to pinacolone include the reaction of pivaloyl chloride [3282-30-2] with Grignard reagents (28) and the condensation of neopentanoic acid with acetic acid using a rare-earth oxide catalyst (29). Amides of neopentanoic acid can be prepared direcdy from the acid, from the acid chloride, or from esters, using primary or secondary amines. 

Titan-s ure, /. titanic acid. -sMureonhydrid, n. titanic anhydride, titanium dioxide (TiOj). -schwefelsdure,/. titanosulfmic acid, -stahl, m. titanium steel, -stickstoff, m. titanium nitride, -verbindung, /. titanium compound, -weiss, n. titanium white. 

The production of acetic acid from n-butene mixture is a vapor-phase catalytic process. The oxidation reaction occurs at approximately 270°C over a titanium vanadate catalyst. A 70% acetic acid yield has been reported. The major by-products are carbon oxides (25%) and maleic anhydride (3%) ... 

Titanium Dioxide (Titania, Titanium White, Rutile, Anatase, Brookite, Titanic Anhydride, Titanic Acid Anhydride, Titanic Oxide). Ti02, mw 79.90, Selected Parameters of the Allotropic Forms of Ti02... 

Treatment of N-benzoyl-L-alanine with oxalyl chloride, followed by methanolic triethylamine, yields methyl 4-methyl-2-phenyloxazole-5-carboxylate 32 <95CC2335>. a-Keto imidoyl chlorides, obtained from acyl chlorides and ethyl isocyanoacetate, cyclise to 5-ethoxyoxazoles by the action of triethylamine (e.g.. Scheme 8) <96SC1149>. The azetidinone 33 is converted into the oxazole 34 when heated with sodium azide and titanium chloride in acetonitrile <95JHC1409>. Another unusual reaction is the cyclisation of compound 35 to the oxazole 36 on sequential treatment with trifluoroacetic anhydride and methanol <95JFC(75)221>. 

Friedel-Crafts acylation reactions of aromatics are promoted by Tilv complexes.104 In some cases, a catalytic amount of the titanium compound works well (Scheme 28). In addition to acyl halides or acid anhydrides, aldehydes, ketones, and acetals can serve as electrophile equivalents for this reaction.105 The formylation of aromatic substrates in the presence of TiCl4 is known as the Rieche-Gross formylation metalated aromatics or olefins are also formylated under these conditions.106... 

Ethyl sulfate Flammable liquids Fluorine Formamide Freon 113 Glycerol Oxidizing materials, water Ammonium nitrate, chromic acid, the halogens, hydrogen peroxide, nitric acid Isolate from everything only lead and nickel resist prolonged attack Iodine, pyridine, sulfur trioxide Aluminum, barium, lithium, samarium, NaK alloy, titanium Acetic anhydride, hypochlorites, chromium(VI) oxide, perchlorates, alkali peroxides, sodium hydride... 

A new and direct method for the synthesis a range of 2-azetidinones (/3-lactams) has been developed by Sharma and Kanwar via condensation of titanium enolate 83 of various mixed anhydrides with different imines (Scheme 33).116... 

Reactions of titanocene-methylidene generated from titanacyclobutanes with acyl chlorides 55 [46] or acid anhydrides 56 [47] lead initially to the titanium enolates 57 (Scheme 14.24), which then afford aldols upon treatment with the carbonyl compounds. On the other hand, five-membered cyclic anhydrides are methylenated with dimethyltitanocene (Table 14.5, entry 7) [45]. 

In 1990, Choudary [139] reported that titanium-pillared montmorillonites modified with tartrates are very selective solid catalysts for the Sharpless epoxidation, as well as for the oxidation of aromatic sulfides [140], Unfortunately, this research has not been reproduced by other authors. Therefore, a more classical strategy to modify different metal oxides with histidine was used by Moriguchi et al. [141], The catalyst showed a modest e.s. for the solvolysis of activated amino acid esters. Starting from these discoveries, Morihara et al. [142] created in 1993 the so-called molecular footprints on the surface of an Al-doped silica gel using an amino acid derivative as chiral template molecule. After removal of the template, the catalyst showed low but significant e.s. for the hydrolysis of a structurally related anhydride. On the same fines, Cativiela and coworkers [143] treated silica or alumina with diethylaluminum chloride and menthol. The resulting modified material catalyzed Diels-Alder reaction between cyclopentadiene and methacrolein with modest e.s. (30% e.e.). As mentioned in the Introduction, all these catalysts are not yet practically important but rather they demonstrate that amorphous metal oxides can be modified successfully. 

Examples Sodium Titanium tetrachloride Boron trifluoride Acetic anhydride Examples Most organic and inorganic materials are not water reactive... 

The phthalic anhydride/urea process may also be employed to convert tetra-chloro phthalic anhydride to green copper hexadecachloro phthalocyanine by condensation. In this case, titanium or zirconium dioxides, particularly in the form of hydrated gels, are used instead of the molybdenum salts which are used in the phthalic anhydride process [23]. There is a certain disadvantage to the fact that the products lack brilliance and require additional purification. 

Copper Perbromo Phthalocyanine Green may also be obtained from tetra-bromo phthalic anhydride by the phthalic anhydride/urea process in the presence of titanium or zirconium catalysts. This route has not yet been introduced on a commercial scale. 

Weakly nucleophilic amines such as 2,4-dinitroaniline are acylated in excellent yields by the mixed anhydride 301, prepared from the trimethylsilyl esters 299 (R = Me, i-Pr, t-Bu, PhCH2CH2, 2-MeCgH4 etc.) and 4-trifluoromethylbenzoic anhydride (300) under titanium(IV) catalysis 340... 

The influence of temperature on the ortho effect has been evaluated in the alkaline hydrolysis in aqueous DMSO solutions of ortho-, meta- and para-substituted phenyl benzoates (26). The alcoholysis of phthalic anhydride (27) to monoalkyl phthalates (28) occurs through an A-2 mechanism via rate-determining attack of the alcohol on a carbonyl carbon of the anhydride (Scheme 4). Evidence adduced for this proposal included highly negative A 5 values and a p value of 4-2.1. In the same study, titanium tetra-n-butoxide and tri-n-butyltin ethanoxide were shown to act as effective catalysts of the half-ester formation from (27), the mechanism involving alkoxy ligand exchange at the metal as an initial step. ... 

Chemical deoxygenation of sulfoxides to sulfides was carried out by refluxing in aqueous-alcoholic solutions with stannous chloride (yields 62-93%) [186 Procedure 36, p. 214), with titanium trichloride (yields 68-91%) [203], by treatment at room temperature with molybdenum trichloride (prepared by reduction of molybdenyl chloride M0OCI3 with zinc dust in tetrahydrofuran) (yields 78-91%) [216], by heating with vanadium dichloride in aqueous tetrahydrofuran at 100° (yields 74-88%) [216], and by refluxing in aqueous methanol with chromium dichloride (yield 24%) [190], A very impressive method is the conversion of dialkyl and diaryl sulfoxides to sulfides by treatment in acetone solutions for a few minutes with 2.4 equivalents of sodium iodide and 1.2-2.6 equivalents of trifluoroacetic anhydride (isolated yields 90-98%) [655]. 

In a novel method of forming cyclobutanols, titanium(IV) chloride is found to promote the condensation of substituted bisketene silyl acetals 23 with more reactive carbon electrophiles such as acetic anhydride or benzoic anhydride. In each experiment, it is apparent that only one diastercomer of the substituted 2,4-dicarbomethoxycyclobutanols 24 is furnished, as can be vindicated by NMR spectral analysis.33... 

Modification of the metal itself, by alloying for corrosion resistance, or substitution of a more corrosion-resistant metal, is often worth the increased capital cost. Titanium has excellent corrosion resistance, even when not alloyed, because of its tough natural oxide film, but it is presently rather expensive for routine use (e.g., in chemical process equipment), unless the increased capital cost is a secondary consideration. Iron is almost twice as dense as titanium, which may influence the choice of metal on structural grounds, but it can be alloyed with 11% or more chromium for corrosion resistance (stainless steels, Section 16.8) or, for resistance to acid attack, with an element such as silicon or molybdenum that will give a film of an acidic oxide (SiC>2 and M0O3, the anhydrides of silicic and molybdic acids) on the metal surface. Silicon, however, tends to make steel brittle. Nevertheless, the proprietary alloys Duriron (14.5% Si, 0.95% C) and Durichlor (14.5% Si, 3% Mo) are very serviceable for chemical engineering operations involving acids. Molybdenum also confers special acid and chloride resistant properties on type 316 stainless steel. Metals that rely on oxide films for corrosion resistance should, of course, be used only in Eh conditions under which passivity can be maintained. 

Thenaldehyde (thiophene-2-carbaldehyde) is readily available via the Vilsmeier-Haack reaction of DMF with thiophene catalyzed by phosphorus oxychloride. The Sommelet reaction with 2-chloromethylthiophene also gives reasonable yields (63AHC(l)l). Likewise, thiophene is readily acylated with acyl anhydrides or acid chlorides (equation 14), using mild Friedel-Crafts catalysts, such as tin(IV) chloride, zinc chloride, boron trifluoride, titanium tetrachloride, mercury(II) chloride, iodine and even silica-alumina gels or low-calcium-content montmorillonite clays (52HC(3)l). 

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