Oxidation isomeric forms

Reactions of /l-Butane. The most important industrial reactions of / -butane are vapor-phase oxidation to form maleic anhydride (qv), thermal cracking to produce ethylene (qv), Hquid-phase oxidation to produce acetic acid (qv) and oxygenated by-products, and isomerization to form isobutane. 

Henkel Rearrangement of Benzoic Acid and Phthalic Anhydride. Henkel technology is based on the conversion of benzenecarboxyhc acids to their potassium salts. The salts are rearranged in the presence of carbon dioxide and a catalyst such as cadmium or zinc oxide to form dipotassium terephthalate, which is converted to terephthahc acid (59—61). Henkel technology is obsolete and is no longer practiced, but it was once commercialized by Teijin Hercules Chemical Co. and Kawasaki Kasei Chemicals Ltd. Both processes foUowed a route starting with oxidation of napthalene to phthahc anhydride. In the Teijin process, the phthaHc anhydride was converted sequentially to monopotassium and then dipotassium o-phthalate by aqueous recycle of monopotassium and dipotassium terephthalate (62). The dipotassium o-phthalate was recovered and isomerized in carbon dioxide at a pressure of 1000—5000 kPa ( 10 50 atm) and at 350—450°C. The product dipotassium terephthalate was dissolved in water and recycled as noted above. Production of monopotassium o-phthalate released terephthahc acid, which was filtered, dried, and stored (63,64). 

Phenazine mono-N-oxides have also been prepared from nitrobenzene derivatives. Condensation of nitrobenzene with aniline using dry NaOH at 120-130 °C results in modest yields of phenazine 5-oxide, although the precise mechanism of this reaction is not well understood (57HC(ll)l) with unsymmetrical substrates it is not possible to predict which of the isomeric fV-oxides will be produced. Nitrosobenzene derivatives also function as a source of phenazine mono-fV-oxides thus, if 4-chloronitrosobenzene is treated with sulfuric acid in acetic acid at 20 °C the fV-oxide is formed (Scheme 21). 

Two pieces of chemical evidence support the three-membered ring formulation. The bifunctional oxazirane prepared from glyoxal, tert-butylamine, and peracetic acid (6) can be obtained in two crystalline isomeric forms. According to the three-membered ring formula there should be two asymmetric carbon atoms which should allow the existence of meso and racemic forms. A partial optical resolution was carried out with 2-7i-propyl-3-methyl-3-isobutyloxazirane. Brucine was oxidized to the N-oxide with excess of the oxazirane. It was found that the unused oxazirane was optically active. 

This compound has an octahedral coordination sphere slightly distorted towards a trigonal prism. Oxidation by air leads to Ru2(S2CNEt2)5 which exists in two isomeric forms (Figure 1.52) [138]. 

The oxygen atoms of the homo cyclic oxides occupy axial positions in solid S7O and SsO. In fact, recent ab initio MO calculations at the G3X(MP2) level of theory have demonstrated that these isomers are, by 7 and 9 kj mol respectively, more stable than the alternative structures with the oxygen atoms in equatorial positions [89]. In the case of SsO, however, the energy difference is only 1 kJ mol and the conformation with the oxygen atom in the equatorial position is more stable. This result agrees with the observation that SsO exists as two isomeric forms in the solid state depending on the crystallization conditions (see above). 

The enantiomerically pure indolizidine (—)-422 has been synthesized starting from L-malic acid diethyl ester 407. The hydroxyl function of L-malic acid diethyl ester 407 has been protected as dihydropyranyl ether 408 with 2/7-dihydropyran and Amberlyst 15 in pentane at room temperature. The diethyl ester 408 was then reduced with lithium aluminium hydride in diethyl ether under reflux and the newly generated hydroxyl functions then protected with mesyl chloride in the presence of triethylamine in dichloromethane at 0°C. This was converted into newly protected pyrroline nitrone 409 in 44% overall yield through a well-established method (Scheme 90). The regio-isomeric 5-pyrroline-iV-oxide 410 formed in 4% overall yield was easily separated by column chromatography <20000L2475>. 

Ajoene (Spanish, ajo, garlic), 4,5,9-trithiadodeca-l,6,ll-triene-9-oxide 35 (Scheme 12), an antithrombotic compound with other well-defined physiological properties, is formed from allicin.84 Like allicin, ajoene is a sulfoxide but has two further sulfur atoms in a disulfide linkage. E and Z isomeric forms are possible involving the C=C bond at positions 6 and 7. Ajoene is somewhat more stable than allicin. The formation of ajoene probably involves condensation of 2 molecules of allicin forming a sulfonium salt 33, with elimination of propenesulfenic acid. Elimination of a second molecule of propenesulfenic acid... 

Hydrogenation of pyrene Hydrogenation experiments were carried out with an oxide and a presulphided catalyst and the analysis of the products is shown in Table V, from which it can be seen that the distribution of the products for both catallysts was similar. The principal hydrogenation products were dihydropyrene and hexahydropyrene and lesser amounts of the tetra and decahydro-derivatives were also detected. Two isomeric forms were found for both the hexahydro and decahydro-derivatives. For the hexahydro-derivatives, 1,2,3,6,7,8 hexahydropyrene was the more abundant (ratio 4 3). 

Sarel and co-workers have examined some reactions of alkynylcyclopropanes with iron carbonyl compounds [1]. Treatment of cyclopropylacetylene (5) with iron pentacarbonyl under photolytic conditions gives, after cerium(IV) oxidation, isomeric quinones 6 and 7, derived from two molecules of 5 and two carbonyls with both cyclopropane rings intact [6]. Furthermore, the photoreaction of dicyclopropylacetylene (8) with iron carbonyl gives some ten different products depending on the reagents and the reaction conditions, and some of them have the cyclopentenone skeleton formed by the opening of cyclopropane ring coupled with carbonyl insertion [7] (Scheme 2). 

Hi. Lysine. Gamma radiolysis of aerated aqueous solution of lysine (94) has been shown, as inferred from iodometric measurements, to give rise to hydroperoxides in a similar yield to that observed for valine and leucine. However, attempts to isolate by HPLC the peroxidic derivatives using the post-column derivatization chemiluminescence detection approach were unsuccessful. This was assumed to be due to the instability of the lysine hydroperoxides under the conditions of HPLC analysis. Indirect evidence for the OH-mediated formation of hydroperoxides was provided by the isolation of four hydroxylated derivatives of lysine as 9-fluoromethyl chloroformate (FMOC) derivatives . Interestingly, NaBILj reduction of the irradiated lysine solutions before FMOC derivatization is accompanied by a notable increase in the yields of hydroxylysine isomers. Among the latter oxidized compounds, 3-hydroxy lysine was characterized by extensive H NMR and ESI-MS measurements whereas one diastereomer of 4-hydroxylysine and the two isomeric forms of 5-hydroxylysine were identified by comparison of their HPLC features as FMOC derivatives with those of authentic samples prepared by chemical synthesis. A reasonable mechanism for the formation of the four different hydroxylysines and, therefore, of related hydroperoxides 98-100, involves initial OH-mediated hydrogen abstraction followed by O2 addition to the carbon-centered radicals 95-97 thus formed and subsequent reduction of the resulting peroxyl radicals (equation 55). 

Carbonyl-substituted nitrones are formed as mixture of (E)- and (Z)-stereo-isomers. By coordination to a Lewis acid, the (Z)-isomers are expected to be more stabilized due to tight complexation. Thus, a 2.8 1 ( /Z)-mixture of A -(methoxy-carbonylmethylene)methylamine A -oxide isomerizes to the (Z)-isomer in the presence of MgBr2-Et20 and undergoes a regio- and exo-selective cycloaddition reaction to 2-propen-l-ol to give the isoxazolidine-5-methanol as a single product... 

As stated in Section 5.17.1.4, simple thiepins (e.g. 44) are generally too reactive to be isolable under ambient conditions. Thiepins (49), (50) and (51) are among the relatively few stable monocyclic thiepins to have been reported and the majority of reactivity studies on thiepins have been carried out on polycyclic thiepins. The chemical reactivity of thiepins can be considered separately from the reactivity of the valence tautomeric thianorcaradienes more readily than was the case for oxepins-arene oxides. A spontaneous thermal extrusion of sulfur appears to occur from the episulfide tautomer of thiepins and the stable thiepins (49)-(51) would thus appear to exist exclusively in this valence isomeric form. 

Problem 16.53 Deduce a possible structure for each of the following, (a) Compound (A), CftHdilute acid and base and its dipole moment is zero, (b) Compound (B). CgH,NO, is insoluble in dilute acid and base. (B) is transformed by KMnO, in HjS04 to compound (C), which is free of N, soluble in aqueous NaHCO, and gives only one mononitro substitution product, (c) Compound (D), C,H,N02, undergoes vigorous oxidation to form compound (E), C,HjN04, which is soluble in dilute aqueous NaHCOj and forms two isomeric monochloro substitution products. ... 

Potassium Tetrachloro-dipyridino-iridite, [Ir "pv2Cl4]K, is formed in the same manner as the mono-pyridino-compound, but on longer heating. The substance occurs in two isomeric forms, one orange-yellow, the other red. On oxidation with chlorine or nitric acid, tetra-chloro-dipyridino-iridium, [Irrvpy2CI4], is produced. It is a crystalline body, and with potassium iodide yields potassium tetrachloro-dipyridino-iridite thus ... 

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