Chromium hydro

Again, as with pyridopyrimidines, the main reaction is oxidation of di- or poly-hydro derivatives to fully aromatic structures, often merely by air or oxygen. In some cases the reagent of choice is mercury(II) oxide, whilst other reagents used include sulfur, bromine, chloranil, chromium trioxide-acetic acid, hydrogen peroxide, and potassium ferricyanide, which also caused oxidative removal of a benzyl group in the transformation (306) (307)... 

The broad spectrum of the raw goods occurring in the leather and fur industry [95] necessitates various wet treatment processes in which surfactants and emulsifiers play a big role, e.g., in the regeneration of raw goods, which are preserved with salt, or by drying short-chain sulfosuccinates. To achieve hydro-phobizing effects, sulfosuccinate as emulsifiers are fixed on the surface by salts of aluminum or chromium. 

The aqueous chemistry of chromium(in) above 100 °C has been investigated with particular reference to corrosion phenomena and the possibility of hydro-thermal synthesis of chromite in serpentine rocks. Isotopic exchange studies have indicated that the CrO unit exchanges intact between [Cr(H20)6] and [CrMo6024H6] . This appears to be the first established exchange of such a unit. ° [CrlHjOljlEtOH)] has a stability constant of 6.5 x 10" and is only stable in perchlorate solutions with >80% EtOH. ... 

The complex of tartaric acid and antimony (emetic) was described three centuries ago. Nevertheless, the structure of this compound has been elucidated these last fifteen years by X-ray diffraction ( 1 ). In fact, emetic presents a binuclear cyclic structure. Many authors mentioned similar complex with transition metals (vanadium (2), chromium (3)) or metalloids (arsenic (4), bismuth (5)). Emetic with phosphorus was not mentioned. Nevertheless, tartaric acid or alkyl tartrates has been utilized in phosphorus chemistry tartaric acid reacts with trialkyl phosphites giving heterocyclic phosphites (6). Starting from alkyl tartrates, we prepared spirophosphoranes with a P-H bond and sixco-ordinated compounds (7). With unprotected tartaric acid, many possibilities appear condensation as a diol, as a di(oc-hydro-xyacid), or even as a 8-hydroxyacid. 

Bruns and Haufe have described the first examples of a transition metal complex mediated asymmetric ring opening (ARO) of both meso- and racemic epoxides via formal hydro-fluorination [23]. Initial attempts with chiral Euln complexes led to very low asymmetric induction. Opening of cyclohexene oxide 30 with potassium hydrogendifluoride in the presence of 18-crown-6 and a stoichiometric amount of Jacobsens chiral chromium salen complex 29 [24a] finally yielded two products 31 and 32 in a 89 11 ratio and 92% combined yield, the desired product 31 being formed with 55% ee. Limiting 29 to a catalytic amount of 10 mol% led to an increase in the ratio of 31, however, with the enantiomeric excess dropping to 11% (Scheme 5). 

Even the distorted boat-like deck in [2.2]metacyclophanes can be constructed by an intramolecular version of the benzannulation. A suitable precursor bears a chromium vinylcarbene and an allcyne moiety linked to a meta-phenylene core by two-atom bridges, as shown for complexes 80. Benzannulation under the typical conditions affords hydro-quinonophanes 81 in fair yields (Scheme 31) [73]. Interestingly, the intramolecular benzannulation approach even tolerates heteroatom bridges, which impose both additional strain and helicity on the cyclophane skeleton [73b]. 

The third question in 3D MESA - the dimension of the smallest pieces that can self-assemble - motivated experiments with metallic, polyhedral, 10- xm-sized plates [ref. 63]. The fabrication of 10- xm-sized polyhedra is difficult, so these experiments examined the self-assembly of flat plates, which were easily obtained at this scale. Photolithography, electrodeposition, and electron beam evaporation provided a convenient way to form plates having surfaces whose properties could be modified selectively. The surfaces of these plates consisted of either gold or chromium. Treatment with a long-chained alkanethiol formed a hydrophobic SAM on the gold with a phosphonic acid-terminated thiol, a hydrophilic one. Similarly, a phosphonic acid-terminated thiol formed a hydro-phobic SAM on chromium (through coordination of the acid with surface Cr... 

The easy hydrogenolysis of 1,3-cyclohexanedione over palladium catalyst has been applied to the preparation of 3,3-dimethylcyclohexanone from 5,5-dimethyl-1,3-cyclohexanedione (eq. 5.40).129 The reaction pathway outlined in Scheme 5.7 has been suggested for this transformation. 1,3-Cyclohexanedione was also hydro-genolyzed to give cyclohexanol in a 95% yield over copper-chromium oxide at 200°C and 17.7 MPa H2.130... 

Chromates, dichromates, etc., are readily reduced, e.g. by hydro-clrloric acid (with evolution of chlorine), by sulphurous acid (ivith formation of sulphate and dithionatc), by hydrogen sulf>hide (ivith separation of sulphur), by ferrous salts, by alcohol, etc., the solution simultaneously becoming green owing to the formation of a chromic salt. The chromates of the more feebly electro-positive elements decompose w hen strongly heated, with formation of chromium sesquioxide dichromates of other metals yield normal chromates, chromium sesquioxide, and oxygen. ... 

Starting material. The preparation given below is based on an improved method. Here the bromide salt is obtained from crude c/s-[aquabis(ethylene-diamine)hydroxochromium(III)] dithionate (Sec. F) by treatment with hydro-bromic acid. The pure c/s-[diaquabis(ethylenediamine)chromium(IIl)] bromide is used to prepare pure cfs-[aquabis(ethylenediamine)hydroxochromium(III)] dithionate (Sec. F). 

Cleaning Up Dichloromethane should be placed in the halogenated organic waste container. The chromium salts should be dissolved in hydro-... 

NjPtSioHg, Platinate(II), bis(pentasuIfido)-, bis(tetrapropylammonium), 21 13 NzPtSijHg, Platinate(IV), tris(penta-sulfido)-, diammonium, 21 12, 13 N2SCH4, Urea, thio-chromium(O) complexes, 23 2 N2SC2, Sulfur dicyanide, 24 125 N2SC4H6, 2H-Imidazole-2-thione, 1,3-di-hydro-1-methyl-cobalt complexes, 23 171 N2SCSH12, Thiourea, N,N,N methyl-... 

Metal oxides, sulfides, and hydrides form a transition between add-base and metal catalysts. They catalyze hydro nation-dehydrogenation as well as many of the reactions catalyzed by adds such as cracking and isomerization. Their oxidation activity is related to the possibility of two valence states which allow oxygen to be released and reabsorbed alternately. Common examples are oxides of cobalt, iron, zinc, and chromium and hydrides of predous... 

In deaerated 1 N H2SO4 (pH = 0.56), hydrogen-ion reduction is the cathodic reaction with the cathodic polarization curve intersecting the iron, nickel, and chromium curves in the active potential region. Hence, active corrosion occurs with hydrogen evolution, and the corrosion rates would be estimated by the intersections of the curves. The curves predict that the titanium will be passivated. However, the position ofthe cathodic hydrogen curve relative to the anodic curves for titanium and chromium indicates that if the exchange current density for the hydro-... 

LIQUID AMMONIA (7664-41-7, anhydrous, compressed gas or cryogenic liquid 1336-21-6, solution in water) Difficult to ignite, but can detonate in confined spaces in fire. Reacts violently with strong oxidizers, acids (nitric, hydrochloric, sulfuric, picric, hydro-bromic, hydrochlorous, etc.). Shock-, temperature-, and pressure-sensitive compounds are formed with antimony, chlorine, germanium compounds, halogens, heavy metals, hydrocarbons, mercury oxide, silver compounds (azides, chlorides, nitrates, oxides). Fire and/or explosions may be caused by contact with acetaldehyde, acrolein, aldehydes, alkylene oxides, amides, antimony, boron, boron halides, boron triiodide, bromine, bromine chloride, chloric acid, chlorine, chlorine monoxide, o-chloronitrobenzene, l-chloro-2,4-dinitrobenzene, chlorosilane, chloromelamine, chromium trioxide, chromylchloride, epichlorohydrin, fluorine, hexachloromelamine, hypochlorites (do not mix ammonia with liquid household... 

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