Carbonyl quinones

The Patterno-Buchi coupling of various stilbenes (S) with chloroanil (Q) to yield fran -oxetanes is achieved by the specific charge-transfer photo-activation of the electron donor-acceptor complexes (SQ). Time-resolved spectroscopy revealed the (singlet) ion-radical pair[S+% Q" ] to be the primary reaction intermediate and established the electron-transfer pathway for this Patterno-Buchi transformation. Carbonyl quinone activation leads to the same oxetane products with identical isomer ratios. Thus, an analogous mechanism is applied which includes an initial transfer quenching of the photo-activated (triplet) quinone acceptor by the stilbene donors resulting in triplet ion-radical pairs. ... 

Quinones, Semiquinones, and Catechols. All molecules with unsaturated bonds (olefins, acetylenes, aromatics, carbonyls, quinones, etc.) have a degree of electrophilicity and electron affinity. Within a class, the extent of conjugation... 

Two chiral manganese(III) salen catalysts, bearing different chiral diamine bridges (Figure 8.5) [74] were anchored by direct axial coordination of the metal center onto the phenolate groups created by sodium hydroxide treatment of an air-oxidized AC, as confirmed by XPS and TPD the air activation of these materials introduced mainly phenol and carbonyl-quinone groups that upon reflux with a sodium hydroxide solution were converted into phenolates. This method was also applied to anchoring of the Jacobsen catalyst onto air-oxidized CXs... 

One can also envision that the quinone could trap the hydridopalladium species resulting from the B-hydrogen elimination that releases the oxidized organic product (Equation 16.129). Insertion of quinone into the palladium hydride would form an enolate that would tautomerize to the phenoxide complex. Protonation with the reagent containing an 0-H or N-H bond would generate the free hydroquinone and Pd(II). As noted in Chapter 17 on carbonylation, quinone has been used as an additive with this mechanism in mind to prevent tire Pd(II) hydroesterification catalysts from undergoing reduction to palladium(O). ... 

The surface chemistry of a carbon is known to play a crucial role in many applications, most notably in adsorption and catalysis [91-94]. It has been observed that the surface of templated porous carbons mainly has oxygen-containing functional groups, such as carboxyl, carbonyl, quinone, and hydroxyl [76,94,95]. Such groups, especially the carboxyls, can be eliminated by high-temperature... 

Several chemical groups of different stability on the carbon surfaces were recognized as carboxylics, phenols, lactones, carbonyls, quinones and hydroquinones. The TPD profiles were distinctly different, carbon for carbon, indicating differences in the stability of the carbon surface groups. The activated carbon, CAL, has the highest contents of surface oxygen complexes. 

The contribution of surface active groups to the interface capacitance is increased by oxidation, and decreased by a heat treatment in an inert or reducing atmosphere. Kinoshita and Bett (49) have studied the oxidation of carbon black (Vulcan XC72) In chromic acid and found that a reversible peak develops In the cyclic voltammogram at 0.5 - 0.6 volt vs. SHE) with an increasing level of oxidation. This type of reaction is associated with oxidation and reduction of carbonyl/quinone groups. Numerous other studies of the electrochemical activity of species on carbon surfaces have been reported and are collected and summarized by Kinoshita (18). 

Figure 2b shows CO evolution which occurs in the temperature range between 750 K to 1173 K. It is possible to associate the peak around 750 K to anhydrides, the shoulder at 1050 K to phenol groups and finally last peak at 1170 K to carbonyl/quinone groups. The sample functionalized with hydrogen peroxide does not exhibit peaks referable to phenol but only one peak referable to quinone/carbortyl in almost similar amounts as for nitric acid treatment. 

---