Ozonides Palladium

Palladium Arsenic, carbon, ozonides, sulfur, sodium tetrahydridoborate... 

Ozonoiysis is a reaction used with unsaturated hydrocarbons when preparing aldehydes and ketones, by reducing intermediate ozonide or acids by oxidation. The reducing agents used include hydrogen in the presence of palladium, and zinc in acid medium. 

Palladium Paraformaldehyde Paraldehyde Pentaborane-9 Pentacarbonyliron Arsenic, carbon, ozonides, sulfur, sodium tetrahydridoborate Liquid oxygen Alkalies, HCN, iodides, nitric acid, oxidizers Dimethylsulfoxide Acetic acid, nitric oxide, transition metal halides, water, zinc... 

Polymeric alkene ozonides are shock-sensitive that of trans -2-butene exploded when exposed to friction in a ground glass joint. The use of GLC to analyse crude ozonisation products is questionable because of the heat-sensitivity of some constituents [4], Ozonides are decomposed, sometimes explosively, by finely divided palladium, platinum or silver, or by iron(II) salts [5]. Individually indexed compounds are ... 

Reduction of ozonides is very useful, especially when aldehydes are the desired products. Ozonides are easily hydrogenolyzed over palladium [670], or reduced by zinc in acetic acid [671], usually in good yields. Ozonolysis of methyl oleate followed by hydrogenation over 10% palladium on charcoal... 

AH-1,4-Benzothiazine 1,1-dioxide may be synthesized from the sulfone (340) by ozonolysis and hydrogenation of the ozonide over palladium on carbon (Scheme 35) (68TL1041). 

AH- 1,4-Benzothiazine 1,1-dioxide may be synthesized from the sulfone (260) by ozonoly-sis and hydrogenation of the ozonide over palladium on carbon (Scheme 117) (68TL1041). Phenothiazine 5,5-dioxides are produced when 2-nitrodiphenyl sulfones are reduced with triethylphosphite, this being simply an extension of a method described earlier (see Scheme 113). 

These substances, like most compounds with peroxide (O—O) bonds, may explode violently and unpredictably. Therefore ozonizations must be carried out with appropriate caution. The general importance of these reactions derives not from the ozonides, which usually are not isolated, but from their subsequent products. The ozonides can be converted by hydrolysis with water and reduction, with hydrogen (palladium catalyst) or with zinc and acid, to carbonyl compounds that can be isolated and identified. For example, 2-butene... 

For preparative purposes the cleavage of the ozonide is best carried out by catalytic hydrogenation over palladium hydroxide-on-calcium carbonate, a catalyst system which does not hydrogenate the aldehydic products the yield of the latter are usually fairly good. An alternative procedure for the decomposition of the ozonide is treatment with dimethylsulphide in methanol the use of the less obnoxious thiourea is a good alternative.107... 

The fact that the decomposition of ozonides is catalyzed by finely divided metals (silver, platinum, palladium) and metal salts such as ferrous sulfate suggests a free-radical mechanism.23 2-Butene ozonide is broken down with dilute ferrous sulfate solution into acetic acid and acetaldehyde.23... 

Ozonides are rarely isolated [75, 76, 77, 78, 79], These substances tend to decompose, sometimes violently, on heating and must, therefore, be handled with utmost safety precautions (safety goggles or face shield, protective shield, and work in the hood). In most instances, ozonides are worked up in the same solutions in which they have been prepared. Depending on the desired final products, ozonide cleavage is done by reductive or oxidative methods. Reductions of ozonides to aldehydes are performed by catalytic hydrogenation over palladium on carbon or other supports [80, 81, 82, S3], platinum oxide [84], or Raney nickel [S5] and often by reduction with zinc in acetic acid [72, 81, 86, 87], Other reducing agents are tri-phenylphosphine [SS], trimethyl phosphite [89], dimethyl sulfide (DMS) [90, 91, 92], and sodium iodide [93], Lithium aluminum hydride [94, 95] and sodium borohydride [95, 96] convert ozonides into alcohols. 

A much more frequently used reaction is the cleavage of unsaturated compounds to aldehydes (equations 98 and 99). Alkenes and cycloalkenes that possess one or two hydrogens at the double bonds are oxidized by ozone to ozonides, which have to be reduced to prevent a subsequent oxidation to acids by the excess oxygen atom. Reductions are carried out, usually without isolation of the ozonides, by catalytic hydrogenation over palladium catalyst [80, 81,1106] or Raney nickel [55] or by treatment with... 

Alkenes are reduced by addition of H2 in the presence of a catalyst such ozonide, 253 as platinum or palladium to yield alkanes, a process called catalytic hydropolymer, 256 genation. Cis-l,2-diols can be made directly from alkenes by hydroxyla-... 

PALLADIUM BLACK (7440-06-4) Powdered form is highly reactive catalyst, and may cause fire and explosions on contact with many substances, including oxidizers, acetone, strong acids, finely divided aluminum, dioxygen difluoride, ethyl alcohol, hydrazine, hydrogen peroxide, lithium, methyl hydroperoxide, nitrosyl chloride, ozonides, peroxymonosulfu-ric acid, red phosphorus. Incompatible with ammonia, arsenic, chlorine dioxide, hydrogen, methyl hydroperoxide, selenium, tellurium, vanadium dichloride. 

Aldehydes can be obtained homogeneously from ozonides by reductive cleavage, which can be effected either by zinc in glacial acetic acid or by catalytic hydrogenation of the ozonide118,119 in the presence of a 1 19 palladium-calcium carbonate catalyst.120 Adipdialdehyde has thus been obtained from cyclohexene in 60-70% yield 121... 

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