C6H6 oxidation

Aminosalicylic acid (5-amino-2-hydroxybenzoic acid) [89-57-6] M 153.1, m 276-280 , 283 (dec), pK 2.74 (CO2H), pK 5.84 (NH2). Cryst as needles from H2O containing a little NaHS03 to avoid aerial oxidation to the quinone-imine. The Me ester gives needles from C6H6, m 96°, and the hydrazide has m 180-182° (From H2O). [Fallab et al. Helv Chim Acta 34 26 1951, Shavel J Amer Pharm Assoc 42 402 1953.]... 

Diphenylhydrazine (hydrazobenzene) [122-66-7] M 184.2, m 34°, 44°, 175°/10mm, 222°/40mm, pKe i -1.7. Crystd from hot EtOH containing a little ammonium sulfide or H2SO3 (to prevent atmospheric oxidation), preferably under nitrogen. Dried in a vacuum desiccator. Also crystd from pet ether (b 60-100°) to constant absorption spectrum. HCl, from EtOH has m 163-164°(dec). Picrate, from C6H6, has m 123°(dec). 

Picoline-V-oxide (4-methylpyridine-l-oxide) [1003-67-4] M 109.1, m 182-184 , 185-186 , 186-188 , pK 1.29. Recryst from EtOH-EtOAc, Mc2C0-Et20 or C6H6. [Bullitt and Maynard 7 Am Chem Soc 76 1370 1954 Boekelheide and Linn J Am Chem Soc 76 1286 1954]. 

Perhaps the most familiar example of heterogeneous catalysis is the series of reactions that occur in the catalytic converter of an automobile (Figure 11.12). Typically this device contains 1 to 3 g of platinum metal mixed with rhodium. The platinum catalyzes the oxidation of carbon monoxide and unburned hydrocarbons such as benzene, C6H6 ... 

Since the FeCp(C6H6)+ unit is robust towards oxidation even in concentrated sulfuric acid, oxidation of alkyl substituents upon boiling in aqueous KMn04 solution can be achieved and leads to carboxylic substituents. The mesitylene complex can be oxidized to the mono-, di-, or tri-carboxylic add depending upon the reaction conditions. In the latter case, the decomplexed trimesic acid is obtained [106, 107] Scheme XXII ... 

Bis(aryl)cobalt(II) compounds have been prepared by reaction of R MgX (where R = C6H6 Cl n = 2-4) with Co(PR3)2Cl2.203 They undergo both thermally and oxidatively induced decomposition, with the corresponding biphenyl a product. The reactions of alkyl-cobalt complexes have been reviewed recently, and include thermolysis, photolysis, oxidation, and reduction reactions.25 Homolysis of the Co—C bond is a feature of reactions. 

In the Baeyer-Villiger oxidation of [4.3.3]propellane-8,ll-dione 74 the propellane-bis-lactones formed, 75 and 76, are accompanied by a dispirolactone 77 22. Different product mixtures result when different (acidic or more basic) reaction conditions are employed but it has been shown experimentally for the head-to-tail propellane bis-lactone 75, vis-a-vis the isomeric dispiran 77, the latter appears to be the thermodynamically more stable product, resulting from the former under acidic conditions (p-TsOH/ C6H6, 7 days, r.t.). The structures were established by means of X-ray diffraction and H- and 13C-NMR spectroscopy. 

A mixture of 0.79 g. (a slight excess over 0.001 mol) of [MoS6C6(CF3)6] and 1.54 g. (0.001 mol) of [(C6H6)4As]2[MoS6-C8(CF3)6] in 100 ml. of dry dichloromethane is refluxed for 3 hours with careful exclusion of atmospheric moisture. The mixture becomes very dark blue, almost black. The solvent is removed in vacuo to leave a blue oil. This oil is dissolved in 30 ml. of dry dichloromethane and carefully triturated with dry n-pentane, which causes the product to crystallize. The product is collected on a sintered-glass funnel and washed with two 25-ml. portions of dry n-pentane. The product while still moist with n-pentane is dried over phosphorus(V) oxide in a vacuum desiccator. The yield is 2.1 g. (91%) of very dark crystals, m.p. 189 to 192.5° (checkers report m.p. 190 to 191°). The product is sensitive to reduction by atmospheric moisture. 

This assumption is crucial to the development of a body of thermochemical information on compounds of the transition metals. The assumption is made that b.e.c values are transferable from one compound to another in which the formal oxidation state of the metal is unchanged. This means that, for example, the value of Z (Cr-CO) in Cr(CO)6 is assumed unchanged11 in [Cr(r -C6H6)(CO)3], or that Z)(Cr-C6H6) in the same compound is assumed unchanged from its value in Cr(77-C6H6)2. In this example, A.Hf [Cr(T -C6H6)(CO)3, q] = —352.3 kJ mol-1, from which the enthalpy of disruption, A, for the process... 

Example 20 diallyl-iV,N-diisopropylphosphoroamidite has been prepared by Bannwarth and Kiing and employed in the phosphitylation of the peptide hydroxy function [49]. The phosphitylation by this reagent proceeds in the presence of tetrazole (step a) followed by CBPA oxidation (step b) and removal of allyl protecting groups in the presence of Pd(0)P(C6H6)3 (step c). 

In principle, these oxidations are reversible. This was elegantly shown for silenylium ion 3. Reduction of 3 with t-butylsilyl sodium gives the cyclotetrasilenyl radical 26 and one-electron oxidation of 26 by trityl cation results in the back-formation of 3 (Scheme 13). " Moreover, 26 can be further reduced giving the corresponding anion 27. Also the transformation between radical 26 and anion 27 was shown to be reversible. In this case, the silylated benzenium ion [Et3Si/C6H6] serves as a one-electron oxidant to give the radical 26 (Scheme 13). ... 

Most transition metals form complexes known as carbonyls with carbon monoxide as ligands. Examples include Fe(CO)s, Fe2(CO)9, Cr(CO)6, and Rh6(CO)i6, in all of which the metal is ostensibly in the oxidation state of zero, and many mixed-ligand carbonyls such as Mn(CO)sI, CH3Mn(CO)s, and (C6H6)Mo(CO)3 are known. Such compounds have an organiclike chemistry, being essentially covalent (see Section 8.2 and Chapter 18), and the simple carbonyls such as Ni(CO)4 are volatile liquids that can be purified by fractional distillation. Of all these, however, only Ni(CO)4 (bp 43 °C) forms rapidly (and reversibly) from the elemental metal and CO gas... 

Silver carbonate on Celite has been the preferred reagent for this oxidation (3, 247), but 10-20 equivalents of oxidant is required. In addition the regioselectivity is highly dependent on the solvent. Thus 2 is oxidized by Fetizon s reagent in CH2C12/C6H6 to a 1 1 mixture of 3 and 4-ketopentanol-l (4), but in CHC13 to 3 and 4 in the ratio 9 1. 

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