Quinones, oximes

Quinone dyes, 9 503 Quinone ketals, anodic oxidation of hydroquinone ethers to, 21 264 Quinone methides, 2 209-211 Quinone Michael addition chemistry, 21 248-249, 250, 252 Quinone monoacetals, 21 251 Quinone monoimine (QMI), 19 246 Quinone oximes, formation of,... 

Tautomerism exists in the case of o- and p-nitrosophenols and naphthols which exist mainly as the quinone oximes, and which also give high field shifts. The values for the oxime groups in the 1,2-naphthoquinones, for example, were 229 and 265 ppm for the 1-oxime and the 2-oxime respectively. 

However, in the majority of cases these wells are of very different energies, so that essentially only one of the two states is found. Even in cases where there are measurable concentrations of both tautomers in solution, it may well be that only one occurs in the solid. This is so for the quinone oxime-nitrosophenol system already discussed (34,91), for the monooximes of 1,2- and 1,4-naphthoquinone (91), and for dibenzoylmethane (33) and other 1,3-diketones. Similarly, the furopyridone 42 and the pyranopyridone 43 are in the keto form in the solid, whereas in solution different amounts of enol are also found (92). Compound 44 has recently been shown to exist in the solid only in the 1,4-dihydro form, a (93). 

Quinone oximes and nitrosoarenols are related as tautomers, i.e. by the transfer of a proton from an oxygen at one end of the molecule to that at the other (equation 37). While both members of a given pair of so-related isomers can be discussed separately (see, e.g., our earlier reviews on nitroso compounds and phenols ) there are no calorimetric measurements on the two forms separately and so discussions have admittedly been inclusive—or very often sometimes, evasive—as to the proper description of these compounds. Indeed, while quantitative discussions of tautomer stabilities have been conducted for condensed phase and gaseous acetylacetone and ethyl acetoacetate, there are no definitive studies for any pair of quinone oximes and nitrosoarenols. In any case. Table 4 summarizes the enthalpy of formation data for these pairs of species. 

As such, thermochemical analogies don t help us decide which tautomer is more stable. From the literature we conclude that the quinone oxime tautomer is somewhat the more stable, the precise enthalpy and free energy difference depending on the solvent, substituents and reaction conditions (see the recent paper. Reference 60, and references cited therein). 

If nitrosophenols are in equilibrium with quinone oximes, are nitrosoanilines in equilibrium with quinonimine oximes While in solution, 2-nitrosoanilines appear to show such behavior and crystallographic determination shows the benzenoid form is preferred . The enthalpy of formation of 4-nitrosodiphenylamine—or is it Af -phenyl-p-benzoquinone oxime—has been measured (213.1 3.2 kJmoD ), but as this value is for the solid we hesitate to make any thermochemical comparisons. Perhaps relatedly, the enthalpy of formation of 3,5-dimethyl-4-nitrosopyrazole has been determined but there are no data for any pyrazolones (1,2-diazacyclopentadienones as opposed to pyrazolinones) with which to make comparison with a putative oxime. 

Thermal synthesis of 2-substituted phenanthroxazoles and related compounds by cyclization of O-methyl o-quinone oximes with compounds ArCH2Y (Ar = aryl, hetaryl Y = H, OH, Cl, Br, OAc, SH, COR, NH2) or with amines (PhCHiNMej, PhNHMe, PhNMe2) has been described. Cyclization of a-oxooximes in the system alkyl halide or sulfate/DMF/K2C03 also leads to oxazole derivatives . 

In the course of treating lignin with nitric acid, especially with dilute acid, hydrocyanic acid is evolved. This is. explained by the formation of nitrosophenols that undergo a tautomeric conversion into quinone oximes, the latter then being oxidized and hydrolysed. During these reactions HCN is split off in a manner resembling that reported by Seyewetz [64] (compare Vol. I). 

Quinol inol-5-sulfoni c acid, A086 Quinone, AG08 Quinone oxime, AG49 Quinonimine, AG37 Quinoxaline, AL88 Quinoxaline di-N-oxide, AL94 Quinoxaline 1,4-dioxide, AL9 ... 

Fig. 75 Catalytic cyclopropanation using a cobalt camphor quinone oximate complex...

Along with nitration processes, isomerization processes may take place which in turn may lead to various fairly complex reactions. As a result such products as C02, CO, NH3 are formed. Such reactions are particularly notable in the nitration of phenols. Their mechanism has been explained by Seyevetz [81] in the following way. A phenol undergoes nitrosation under the influence of nitrous acid present in the nitrating acid. Nitrosophenol isomerizes to quinone oxime, which oxidizes at the double bonds to form mesoxalic acid and its oxime ... 

If the para position on the phenol nucleus is occupied, o- quinone oxime is formed and the reaction proceeds in a similar way, but with the formation of oxalic acid and dioxysuccinic acid oxime, which then decomposes, giving off HCN ... 

According to that author, such a typical aromatic nitro compound as 4-nitro-1-naphthol (VII) when reacted with diazomethane, formed not only methyl ether (VIII) but also quinone oxime (IX) in lower yield (16%) ... 

It was known for long time that the 1,5- and 1,8-dinitronaphthalenes react under the action of concentrated sulphuric acid to yield naphthazarine - a valuable compound for dyeing [30], The mechanism of the formation of this compound (based on experiments of Dimroth and Ruck [18a]) probably consists in the transformation of the nitro compounds to quinone-oximes and the reduction of one of the nitro groups by hydroxylamine split off the oxime ... 

Iutennefliate phases of the reriuetinn can l e separate 1 flit ease of o- and jemfropheno), if eoncent rated s t nli n aniline hydrochloride is used as electrolyte <, oh. t. Compi Ciited condensation products are obtained. It seem that mlrosophenols primtirily formed react in the form of quinon " oximes with aniline. 

SYNS ACTOR Q l,4-BEi ZOQL L ONEDIOXINE 2,5-CYCLOHEX. DIENE-l,4-DIONE DIOXIME DIBENZO PQD DIOXIME-1,4-CYCLOHEXA-DIENEDIONE DIOXIME-2,5-CYCLOHEX. DIENE-l,4-DIONE G-M-F NCI-C03850 PQD QDO QUINONE DIOXIME p-QUINONE DIOXIME p-QUINONE OXIME... 

SYNS p-NITROSOPHENOL 4-NITROSOPHENOL QUINONE MONOXIME QUINONE OXIME... 

A method for hydrolyzing -quinone oximes with the aid of cuprous chloride has been described the yields are excellent/ ... 

Quinone Oxime.—However, the same compound may be obtained by a wholly different reaction. Quinone is a di-ketone derivative of benzene related to hydroquinol (p. 636). Its constitution by this relationship is as given below. Now when this di-ketone is treated with hydroxyl amine which is the characteristic reagent for aldehydes and ketones, yielding oximes we obtain a mono-oxime as follows ... 

Quinone Oximes.—The most interesting of the derivatives of quinones are the oximes. As stated in the discussion of the ketone structure for quinones one of the proofs for this constitution is the fact that benzoquinone forms both a mono-and a di-oxime when treated with hydroxyl-amine. The mono- oxime of benzoquinone would have the structure as written below and as given on page 638. Now as previously mentioned, (p. 628), para-nitroso phenol, which is made by the action of nitrous acid upon phenol and the constitution of which is established by other methods of synthesis, (p. 627), proves to be one and the same compound with this mono-oxine of para-benzoquinone, the constitution of which is likewise established by the above reaction of hydroxyl amine upon quinone. This is explained by a rearrangement as shown in the following ,... 

Nitrosoresorcinol illustrates the preparation and properties of the nitroso dyes. The action of nitrous acid on the hydroxy compound gives the dye. These nitrosophenols are isomeric with the quinone oximes, which may also be prepared by the action of hydroxylamine on the quinones. 

The o- and p-nitrosophenols are tautomeric with o- and p-benzoquinone oxime, respectively. Some of the nitrosonaphthols are tautomers of naphthoquinone oximes. A recent publication summarizes the current knowledge of tautomeric equilibria in solution, the composition of the solid phase and the results of theoretical smdies . While tautomeric composition in solution is very much dependent on compound structure and solvent polarity, various nitrosophenols, 2-nitrosonaphthol, l-nitroso-2-naphthol and 4-nitrosonaphthol exist exclusively as quinone oximes in the solid state. 

Diels-Alder reactions of 1235 synthesis of 1228, 1231, 1250, 1335 Quinone oxime tautomers 251, 252 Quinones—see also Aminoquinones, Anthraquinones, Arenolquinones, Benzoquinones, CaUxquinones, Hydroquinones, Hydroxyquinones, Naphthoquinones, Perylenequinones, Scabequinone reduction of 1108 Quinone units 1396... 

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