Oxidative displacement

Halophenols without 2,6-disubstitution do not polymerize under oxidative displacement conditions. Oxidative side reactions at the ortho position may consume the initiator or intermpt the propagation step of the chain process. To prepare poly(phenylene oxide)s from unsubstituted 4-halophenols, it is necessary to employ the more drastic conditions of the Ullmaim ether synthesis. A cuprous chloride—pyridine complex in 1,4-dimethoxybenzene at 200°C converts the sodium salt of 4-bromophenol to poly(phenylene oxide) (1) ... 

The metal-free eyclobutane-1,2-dioxime can be generated by oxidative displacement. It is interesting to note that, unlike ketene dimerization, head-to-head dimerization takes place here. The chromium ketenimine complex 20 is prepared by reaction of the Fischer-type chromium carbene complex with alkyl isocyanides.60 A cyclobutane-1,2,3,4-tetraimine 24 has been reported from the reaction of the ketenimine phosphonium ylide 22.61 Bisimine 23 has been proposed as the intermediate in this transformation. 

Note This reaction is usually done with a Grignard or lithium reagent but oxidative displacement of extranuclear cyano groups may be used in appropriate cases. 

Of particular interest in the present chapter is the effect of test atmosphere on creep and creep damage mechanisms. While there are undoubtedly several factors that can promote creep cavitation and contribute to the observed changes in stress exponent and activation energy, the fact remains that the strain rates are substantially higher in air than in inert atmospheres, as shown in Fig. 8.12. This phenomenon is a direct consequence of the topotactic oxidation reaction of SiC whiskers exposed at the surface. As described by Porter and Chokshi,38 and subsequently by others,21,22 at high temperatures in air, a carbon-condensed oxidation displacement reaction occurs in which graphitic carbon and silica are formed at the whisker interface via... 

Hi. Synthesis of species containing ligands which can be displaced more easily than CO. This is also an extension of the technique employed to activate Os3(CO)i2 and has been widely used in Osg chemistry. When oxidative displacement of carbon monoxide from Osg(CO)i8 and Os5(CO)ig by trimethylamine oxide is carried out in the presence of acetonitrile, the substituted products Osg(CO)i7(MeCN), Osg(CO)ig(MeCN)2 (97,118), and Oss(CO)i s(MeCN) (92) are isolated in good yields. The acetonitrile derivatives of the raft Osg(CO)2i species Osg(CO)(2i )(MeCN) (n = 1,2) have alternatively been synthesized by condensation of Os3(CO)io(MeCN)2 using PdCl2 (99). 

Facile ligand-transfer oxidation of alkyl radicals is accomplished by copper(II) halides or pseudohalides 143a). Two processes occur simultaneously (1) oxidative substitution via cationic intermediates and an alkylcopper species, as in electron-transfer oxidation processes and (2) homolytic atom transfer. The former is akin to the oxidative displacement... 

Reaction (9) presumably proceeds via an intermediate analogous to that produced in Eq. (4). Allyltrifluoroacetate effects oxidative displacement... 

Further examples for the hydrogen peroxide oxidation/displacement reaction are given in the formation of 11 and 12. ° ... 

The oxidative-displacement reaction of allyl compounds RX (R = C3H5, C4H7, C3H4CI X = I, SCN) with [(MeCN)3M(CO)3] (M = Mo, W) gave the metal(II) complexes [(MeCN)2M(CO)2(Tr-allyl)X], which reacted further with bipy, o-phen, diacetylbis(dimethylhydrazone), and CjHj to displace the remaining nitrile groups 170, 253), and with PPh3 to form... 

Routes to homoleptic isocyanide complexes have been defined in thf (Scheme 46). Ta L6 (L = xylyl isocyanide) was reduced by ACg (A = K, Cs) to [Ta 1L6]. This anion appears to be octahedral. Its 13C NMR resonance occured at 210 ppm, the most downfield shift observed for a diamagnetic homoleptic isocyanide complex. Reaction with the NO source N-methyl-N-nitroso-/ -to 1 uenes u 1 lbnam ide provided Ta I(NO)L5 whose essentially linear NbNO fragment is consistent with the formal presence of ligand NO+. Direct nitrosylation of [M (CO)6] with 2 eq [NO][PF6] in the presence of L in CH2C12 at — 60 °C provided r/,v-[M (NO)2L4]1,662 The reaction represents a rare example of non-oxidative displacement of all CO ligands from a homoleptic carbonylme-talate. 

The formation of the same iron-oxygen covalent bonds from either (1) oxidized iron plus oxy anions via electron-transfer (redox) reactions or (2) radical-radical coupling reactions is summarized in Table 3-11. The valence-electron hybridization for the iron center is included as well as the spin state and estimated covalent bond-formation free energy (AGbf)- A similar set of reactions and data for iron-porphyrin compounds is presented in Table 3-12. Section a emphasizes that, just as the combination of a proton with a hydroxide ion yields a covalent H-OH bond (Table 3-11), (1) the combination of protons and porphyrin dianion (Por -) yields covalent porphine (H2Por), and (2) the addition of Lewis acids (Zn2+ or Fe2+) to porphine (H Por) oxidatively displaces protons to give covalent-bonded ZnilPor and Fe iPor. 

The oxidative displacement of hydrazine from 4-hydrazinoquinazoline to form quinazoline was brought about with aqueous copper sulfate or oxygen in ethanolic alkali.This reaction can be usefully adapted for the preparation of deuterated derivatives if deuterated solvents are used. 

Rules for some other reactions make use of information from a database. For example, sodium sulfite will react with silicon dioxide at high temperatures to form sodium silicate and sulfur dioxide. This example follows the general rule nonmetal oxide displacement if... 

Oxidative displacement of U alcohol converts an iodo compou... 

Oxidative displacement of iodoalkanes The combination of chlorine and an licohol converts an iodo compound into an ether. 

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