Ene reactions oxidation with SCO


An active catalytic species in the dimerization reaction is Pd(0) complex, which forms the bis-7r-allylpalladium complex 3, The formation of 1,3,7-octa-triene (7) is understood by the elimination of/5-hydrogen from the intermediate complex 1 to give 4 and its reductive elimination. In telomer formation, a nucleophile reacts with butadiene to form the dimeric telomers in which the nucleophile is introduced mainly at the terminal position to form the 1-substituted 2,7-octadiene 5. As a minor product, the isomeric 3-substituted 1,7-octadiene 6 is formed[13,14]. The dimerization carried out in MeOD produces l-methoxy-6-deuterio-2,7-octadiene (10) as a main product 15]. This result suggests that the telomers are formed by the 1,6- and 3,6-additions of MeO and D to the intermediate complexes I and 2.  [c.424]

Olefin and acetylene complexes of Au(I) can be prepared by direct iateraction of the unsaturated compounds with a Au(I) hahde (190,191). The resulting products, however, are not very stable and decompose at low temperatures. Reaction with Au(III) hahdes leads to halogenation of the unsaturated compound and formation of Au(I) complexes or polynuclear complexes with gold ia mixed oxidatioa states.  [c.386]

The ease with which thiophenes are formed in the reaction of acetylenic epoxides " and of polyacetylenes with hydrogen sulfide is of great interest in connection with the biosynthesis of the naturally occurring thiophenes (cf. Section VIH,A) and also of preparative importance. 2-Methyl-l,2-oxido-5-hexene-3-yne (56) in water containing barium hydroxide reacts with HzS at 50°C to give 4-  [c.27]

Another application of catalyst 8 is to the reaction of acetylenic aldehydes [10c] (Scheme 1.18, Table 1.6). Two acetylenic dienophiles have been reacted with cyclo-pentadiene or cyclohexadiene to give bicyclo[2.2.1]heptadiene or bicyclo[2.2.2]octa-diene derivatives in high optical purity. A theoretical study suggests that this reaction proceeds via an exo transition state.  [c.15]

Oxides. Selenium monoxide [12640-89-0] has only been detected spectroscopically as the gas. Selenium dioxide, Se02, is prepared by burning selenium ia a current of air or oxygen and, optionally, by passiag it over a catalyst or by oxidatioa with nitric acid to selenous acid followed by evaporation to dryness by heating. The compound is white and crystalline with a tetragonal stmcture and is yellowish green as the vapor. It dissolves easily in water forming selenous acid and less readily in acetone, alcohols, glacial acetic acid, and dioxane. Selenium dioxide is less stable than sulfur dioxide or tellurium dioxide. Like sulfur dioxide it is an acid anhydride, but unlike SO2 it is a strong oxidant and is reduced to elemental selenium by sulfur dioxide, hydrogen, hydrogen sulfide, ammonia, phosphoms, carbon, and even organic dust particles in moist air. The reaction with sulfur dioxide does not occur without the presence of water vapor. Selenium dioxide strongly catalyzes the oxidation of nitrogen compounds in Kjeldahl digestion. The use of selenium dioxide as an oxidant in organic chemistry has been reviewed (56). In the gaseous state it is reduced by ammonia and hydrocarbons with emission of light. This gaseous reaction with ammonia was used at one time and in the production of high purity selenium. Selenium dioxide is oxidized by fluorine to Se02F2 and by hydrogen  [c.332]

H2SO.4 concentrations. The standard second-order nitration rate constants ic2 given in Table 1-55 are calculated at Ho —6.60 from the least-square plots of log fcj (obsd) against Ho(T) extrapolated to 25°C according to the method described by Katritzky et al. (378) and corrected for minority species where necessary. Such a standardization allows discussion of substrate reactivities under the same conditions. All the alkyl-thiazoles investigated, and the corresponding quaternary salts, show log k values in the range, -6.9 to -7.5, for reaction in both 4- and 5-positions thus these cations are considerably less reactive than benzene (log k2 = 0.45)(377). A 2-methoxy group has a significant rate-enhancing effect on nitration at the 5-position (ca. three log units), and the negatively charged 2-oxido substituent in 2-thiazolones increases the rate by another six log units. Comparison of nitration rates for the polymethyl derivatives shows that the thiazole 5-position is more reactive than the 4-position by a factor of about two. This agrees with the competitive experiments described earlier (375).  [c.105]

Organometallic compound (Section 14 1) A compound that contains a carbon to metal bond Ortho (Section 117) Term descnbing a 1 2 relationship be tween substituents on a benzene nng Ortho para director (Section 12 9) A group that when present on a benzene nng directs an incoming electrophile to the positions ortho and para to itself Oxidation (Section 2 19) A decrease in the number of elec trons associated with an atom In organic chemistry oxida tion of carbon occurs when a bond between carbon and an atom that is less electronegative than carbon is replaced by a bond to an atom that is more electronegative than carbon Oxidation number (Section 2 19) The formal charge an atom has when the atoms in its covalent bonds are assigned to the more electronegative partner Oxidation state See oxidation number Oxime (Section 17 10) A compound of the type R2C=NOH formed by the reaction of hydroxylamine (NH2OH) with an aldehyde or a ketone  [c.1290]

Amm oxida tion, a vapor-phase reaction of hydrocarbon with ammonia and oxygen (air) (eq. 2), can be used to produce hydrogen cyanide (HCN), acrylonitrile, acetonitrile (as a by-product of acrylonitrile manufacture), methacrylonitrile, hen onitrile, and toluinitnles from methane, propylene, butylene, toluene, and xylenes, respectively (4).  [c.217]

High purity acetaldehyde is desirable for oxidation. The aldehyde is diluted with solvent to moderate oxidation and to permit safer operation. In the hquid take-off process, acetaldehyde is maintained at 30—40 wt % and when a vapor product is taken, no more than 6 wt % aldehyde is in the reactor solvent. A considerable recycle stream is returned to the oxidation reactor to increase selectivity. Recycle air, chiefly nitrogen, is added to the air introducted to the reactor at 4000—4500 times the reactor volume per hour. The customary catalyst is a mixture of three parts copper acetate to one part cobalt acetate by weight. Either salt alone is less effective than the mixture. Copper acetate may be as high as 2 wt % in the reaction solvent, but cobalt acetate ought not rise above 0.5 wt %. The reaction is carried out at 45—60°C under 100—300 kPa (15—44 psi). The reaction solvent is far above the boiling point of acetaldehyde, but the reaction is so fast that Httle escapes unoxidized. This temperature helps oxygen absorption, reduces acetaldehyde losses, and inhibits anhydride hydrolysis.  [c.76]

Reaction with Oxidi ngMgents. Hydrogen chloride and oxygen react in the gaseous state to Hberate chlorine  [c.444]

The equihbrium for the reactions of CO and with the oxides of iron are well estabUshed (see IRON). There is nearly complete conversion of CO to CO2 and H2 to H2O for the reduction of Fe202 to Fe O. Below 570°C, Fe O is reduced directiy to Fe by CO and H2 above 570°C, Fe O first is reduced to FeO which then is reduced to Fe. In the reduction of Fe O to FeO, the conversions of CO and increase with increasing reaction temperature. However, ia the reduction of FeO to Fe, the conversion for H2 increases with increasing reaction temperature, whereas that for CO decreases. This decrease of equihbrium CO conversion with increasing temperature for the reduction of FeO to Fe is not a limitation on the overall conversion because most DR processes are operated usiag countercurrent flow of soHds and reduciag gases. Thus the spent reduciag gas leaves ia coatact with the entering soHds which are ia their highest oxidatioa state, and the equihbrium for the reduction of Fe O to FeO governs the final gas composition. For DR processes that are based on reduction usiag mixtures of CO and H2, the final gas composition usually satisfies the equihbrium for the water gas reaction at the exit temperature, ie,  [c.426]

Oxidation of hydrocarbons by the air dissolved ia fuel is catalyzed by metals and leads to polymer formation, ie, varnish and sludge deposits, by a chain reaction mechanism involving free radicals. Siace it is impossible to exclude air dissolved ia fuel, oxidatioa stabiUty is coatroUed by eliminating species proae to form free radicals and by iatroduciag antioxidants (qv). An accelerated test, the Jet Fuel Thermal Oxidation Test (fFTOT), simulates the critical temperature regimes of the gas turbiae engine fuel manifold and nozzles, ASTM D3241, and has been developed to measure the oxidation stabiUty of aircraft gas turbiae fuels. Ia the JFTOT test, deposits, formed ia the heated test sectioa ia 2.5 h at a specified temperature, are assessed. This relative rating ranks fuels that would normally be expected to operate for thousands of hours ia an engine without deposit formation. In those few iastances when deposits have been observed ia service, the fuel has beea showa to fail JFTOT tests at the specificatioa temperature.  [c.414]

Chlorohydrins from Epoxides. Traditionally epoxides have been manufactured by the dehydrochlotination of chlorohydrins. However, the reverse reaction may be used as a source of chlorohydrins, especially ia the case of ethyleae chlorohydria from ethyleae oxide [75-21-8] which is aow produced by the direct oxidatioa of the olefia. A study of the reactioa of hydrogea chloride with propyleae oxide [75-56-9] showed that an anhydrous system at low temperatures (<0° C) gives the highest yield of chlorohydria with best isomeric selectivity (16).  [c.72]

Electrocyclic reactions of 1,3,5-trienes lead to 1,3-cyclohexadienes. These ring closures also exhibit a high degree of stereospecificity. The ring closure is normally the favored reaction in this case, because the cyclic compound, which has six a bonds and two IT bonds, is thermodynamically more stable than the triene, which has five a and three ir bonds. The stereospecificity is illustrated with octatrienes 3 and 4. ,Z, -2,4,6-Octatriene (3) cyclizes only to cw-5,6-dimethyl-l,3-cyclohexadiene, whereas the , Z,Z-2,4,6-octa-triene (4) leads exclusively to the trans cyclohexadiene isomer. A point of particular importance regarding the stereochemistry of this reaction is that the groups at the termini of the triene system rotate in the opposite sense during the cyclization process. This mode  [c.607]

The prediction on the basis of orbital symmetry analysis that cyclization of eight-n-electron systems will be connotatoiy has been confirmed by study of isomeric 2,4,6,8-decatetraenes. Electrocyclic reaction occurs near room temperature and establishes an equilibrium that favors the cyclooctatriene product. At slightly more elevated temperatures, the hexatriene system undergoes a subsequent disrotatory cyclization, establishing equilibrium with the corresponding bicyclo[4.2.0]octa-2,4-diene  [c.616]

Fatty acids with odd numbers of carbon atoms are rare in mammals, but fairly common in plants and marine organisms. Humans and animals whose diets include these food sources metabolize odd-carbon fatty acids via the /3-oxida-tion pathway. The final product of /3-oxidation in this case is the 3-carbon pro-pionyl-CoA instead of acetyl-CoA. Three specialized enzymes then carry out the reactions that convert propionyl-CoA to succinyl-CoA, a TCA cycle intermediate. (Because propionyl-CoA is a degradation product of methionine, valine, and isoleucine, this sequence of reactions is also important in amino acid catabolism, as we shall see in Chapter 26.) The pathway involves an initial carboxylation at the a-carbon of propionyl-CoA to produce D-methylmalonyl-CoA (Figure 24.19). The reaction is catalyzed by a biotin-dependent enzyme, propionyl-CoA carboxylase. The mechanism involves ATP-driven carboxylation of biotin at Nj, followed by nucleophilic attack by the a-carbanion of propi-onyl-CoA in a stereo-specific manner.  [c.791]

Oxoacid salts of Ge are usually unstable, generally uninteresting, and commercially unimportant. The tetraacetate Ge(OAc)4 separates as white needles, mp 156°, when GeCl4 is treated with TlOAc in acetic anhydride and the resulting solution is concentrated at low pressure and cooled. An unstable sulfate Ge(S04)2 is formed in a curious reaction when GeCl4 is heated with SO3 in a sealed tube at 160°  [c.387]

The fact that the element readily dissolves in aqueous media with disproportionation into PH3 and an oxoacid is immediately clear from the fact that P lies above the line joining PH3 and either H3PO2 (hypophosphorous acid), H3PO3 (phosphorous acid) or H3PO4 (orthophosphoric acid). Phe reaction is even  [c.511]

In principle, complex hydrides (NaBHj, LiAlH ) ought to react similarly with 4-pyrones and lead after treatment with Bronsted or Lewis acids to 4-unsubstituted pyrylium salts. This reaction has not been reported the reduction of 2-pyrones with LiAlH4 results in ring opening. "  [c.262]

The uniform latices containing reactive groups, styrene-acrylonitrile (S/AN) [122] and styrene-glycidy methacrylate (S/GMA) [123] were also prepared by the coreshell emulsion copolymerization and by the soapless emulsion copolymerization method, respectively. In the preparation of P(S/GMA) copolymer particles, S and GMA were copolymerized in an aqueous medium by using potassium peroxydisulfate as the initiator at 65°C. The average size was changed between 0.22-0.44 fxm by changing the initiator concentration and ionic strength of the medium. The reactive oxine groups of the latex particles were modified later by hydrolysis, ammonolysis reaction with NaaS, or periodic acid oxida-  [c.219]


See pages that mention the term Ene reactions oxidation with SCO : [c.343]    [c.214]    [c.23]    [c.437]    [c.127]    [c.321]    [c.491]    [c.512]    [c.744]    [c.64]    [c.426]    [c.393]    [c.666]    [c.386]    [c.568]    [c.341]    [c.27]    [c.34]    [c.752]    [c.1039]    [c.1040]    [c.251]    [c.41]   
Organic synthesis (0) -- [ c.2 , c.119 , c.122 ]