Aromatic rings quinones

Fragmentation Fragmentation occurs on both sides of the carbonyl group. For example, in acetophenone, the major ions occur at masses 77, 105, and 120 (see Figure 20.3). Ions at m/z 39, 50, and 51 also suggest the presence of an aromatic ring. Aromatic compounds, such as quinone, tetralone, and anthraquinone, readily lose CO. 

The phenolic functional group consists of a hydroxyl attached directly to a carbon atom of an aromatic ring. The OH group can also be the consequence of further oxidation or combination with other pollutants such as pesticides, aldehydes, and alcohols (i. e., 2,4-D, cyclic alcohols, cresols, naphthols, quinones, nitrophenols, and pentachlorophenol compounds) forming new more toxic compounds [17,42,160]. 

A rather difficult double Wittig reaction (Eq. 3.24) has been effected with enhanced efficiency under sonication [123], The process constitutes a novel type of annelation of an aromatic ring when applied to o-quinones. 

Periodic acid oxidation will also act on a-hydroxy aldehydes and ketones, a-diketones, a-keto aldehydes, and glyoxal. If the two neighboring hydroxyl groups are on an aromatic ring, the carbon-carbon bond is not cleave but the reactant is still oxidized. Thus, catechol is oxidized to the corresponding quinone. 

Thus, by a combination of oxidation by lignin peroxidases, Mn(II)-dependent peroxidases and other active oxygen species and reductions of some aromatic aldehydes, acids and ketones to the corresponding benzylic alcohols, all aromatic rings in the lignin polymer can be either converted to ring opened products or to quinones/hydroquinones. These products are then further metabolized to CO2 by a currently unknown mechanism. 

Coupling of phenoxy radicals to give dimeric quinone methides 1. Homolytic or heterolytic cleavage of side-chains (Ca-C/ , alkyl-phenyl) and aromatic rings... 

In 1966, Chapman and co-workers proposed a nitro-nitrite photorearrangement as an efficient primary photochemical process for nitroarenes in which the nitro group is out of the plane of the aromatic rings. This is followed by dissociation into NO and a phenoxy-type radical ultimately quinones and other oxy products are formed (Chapman et al., 1966). 

Whereas the reactive species under acidic conditions are the [H2OOH] and [HO] cations, the reactive species under alkaline conditions is the [H02]e anion. Whereas the cationic oxidation species are stronger oxidants, with oxidation potential rising with increasing acidity favoring aromatic ring hydroxylation by electrophilic substitution (3,13), the anionic species mediate a nucleophilic attack on quinones according to the scheme illustrated in Fig. 6 (3,10,11). The formation of new acidic functionality results in a rapid decline in pH. 

Closure of the nonaromatid ring of the anthracycline system has been effected by condensation of a 2-(3-oxobutyl)anthraquinone with nitromethane [135]. After the initial Henry reaction, a Michael-type reaction is induced by the quinone carbonyl in spite of the high electron density of the aromatic ring to be attacked, and the site of attack being a donor. 

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