Quinone monoxime

It can act either as a nitrosophenol or as a quinone monoxime. Coloured derivatives, e.g. the sodium salt, are derived from the quinone form. Direct methylation gives a coloured compound which has been shown to be quino-nemethoxime OlCeH4tNOCH3 p-nitrosoani-sole CH30 C6H4 N0 has been obtained by another route and is colourless. 

When the benzene ring of (1) is strongly activated, the milder electrophilic substitution reactions (nitrosation, azo coupling, and thiocyanation) are readily effected in a manner analogous to the naphthalenes <70RCR923>. Nitrosation of the 4- and 5-hydroxy derivatives of (1) occurs at positions 5 and 4, leading to nitroso derivatives that exist predominantly in the quinone monoxime form <74T3839>. 

This reaction is frequently applied to the preparation of dialkylamines. The dimethylamine evolved in the above reaction may be absorbed by leading through hydrochloric acid from the latter solution the hydrochloride is obtained by evaporation. p-Nitrosophenol, it is to be noted, is tautomeric, in some reactions behaving as quinone monoxime. 

The nitrous acid is usually generated by the action of sodium nitrite on an acid solution. The nitrosophenols are identical with the quinone monoximes, formed by acting on quinone with hydroxylamine. 

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

Nitration takes place easily and again there is a tendency for polysubstitution. Phenols are readily nitrosated by nitrous acid. The resultant nitrosophenols are tautomeric with the corresponding quinone monoximes (Scheme 4.16). 

An investigation of nitrosobenzene in alkaline solution is complicated by the reaction of nitrosobenzene with hydroxyl ions [163,164]. There is a relatively fast, reversible addition of hydroxyl ion to the nitroso group. Besides that, there is in aqueous solutions at pH > 13 in the absence of dioxygen a relatively slow reaction giving mainly a mixture of azoxybenzene and 4-hydroxynitrosobenzene (p-quinone monoxime) in a reaction suggested as involving a hydride ion transfer from the initially formed 4-hydroxycyclohexa-diene oxime anion to nitrosobenzene hydride ion transfer to nitrosobenzene probably also occurs in alcoholic solutions when an alkoxide is present. In the presence of dioxygen, some nitrobenzene is formed. 

Phenol, p-nitroso- Quinone monoxime p-Quinone monooxime Quinone oxime. Yellow crystals mp = 144° (dec) = 1,479 >.m = 228, 311 nm (e = 7610, 11000, MeOH) slightly soluble in H2O, CeHe, CS2 solubie in CHCI3, C7H8, C5H5N, very soluble in EtOH, Et20, Me2CO. 

Nitration of dihydrovomicine proved more difficult (30% nitric acid), but a dinitro derivative has been characterized (16). Reduction of dinitro-dihydrovomicine with tin and hydrochloric acid yields the aminohydro-quinone, CXXX. This is quite understandable if the nitrosophenol (quinone monoxime), CXXIX, is assumed as the intermediate. 

Spectrophotometric procedures, including absorptimetric and fluo-rimetric, will continue to be popular and important because they can be sensitive and accurate, and because the necessary instruments are now famihar laboratory tools. Intrinsically, fluorimetric methods can be several orders of magnitude more sensitive than absorptimetric. To date, most direct fluorimetric methods are for the determination of metals, while anions are determined by their quenching action on fluorescent compounds. Hopefully, other new direct fluorimetric reagents for anions similar to the one described above for cyanide ion using quinone monoxime benzene sulfonate ester will be developed either as the result of chance observations or the application of increased fundamental knowledge of the fluorescence process. There probably will be few if any major advances in the quality of the instruments used in these methods improved methods mainly will be the result of more sensitive and more selective analytical reagents. 

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