Oxygenation anthracene

A chemical process occurs involving the formation of a new substance with corresponding energetic ground state N (Fig. 14, 15/V). For instance, on aluminium oxide or silica gel layers in the presence of oxygen, anthracene initially yields anthra-quinone, that is then oxidized further to yield 1,2-dihydroxyanthraquinone [4, 5]. Alizarin and chrysazin are also formed depending on the properties of the aluminium oxide used [6]. 

Other OTM compounds that are indicated by preliminary studies to be efficient triplet sensitizers include ClRe(C0)2L (Table 12). In dichloromethane at room temperature these complexes are strongly luminescent and photo-inert (41). Under the same conditions, the emissions are quenched by oxygen, anthracene, and trans-stilbene. The trans cis isomerization of trans-stilbene is efficiently sensitized by several of these species. Quantitative sensitization experiments indicated that the luminescing excited states of ClRe(C0)3L are produced with 100 percent... 

Two types of reactions are important in the photochemical transformation of PAHs, those with molecnlar oxygen and those involving cyclization. lllnstrative examples are provided by the photooxidation of 7,12-dimethylbenz[a]anthracene (Lee and Harvey 1986) (Fignre 1.14a) and benzo[a]pyrene (Lee-Ruff et al. 1986) (Figure 1.14b), and the cyclization of CM-stilbene (Figure 1.14c). 

More comprehensive information was obtained [116] about the interaction of singlet oxygen with anthracene films. The quartz microweighing and mass spectrometry were used in tiiis work along with the methods of semiconductor detectors. 

Fig. 5.16. Changes in mass of anthracene weighed sample (batch) against time during its treatment by singlet oxygen [116]...

At room and higher temperatures the pattern of interaction between the singlet oxygen and anthracene changes. Changes in the mass of weighed sample of anthracene being acted upon by C>2( ) at room... 

As discussed in Chapter 2, triplet excited anthracene transfers its energy to oxygen to produce singlet excited oxygen OA,). The singlet oxygen in turn attacks a ground state anthracene to form a 9,10-endoperoxide. 

Those favoring the singlet oxygen mechanism (mechanism B) counter by asking why, if a mole-oxide is formed, must the oxygen be transferred to another anthracene to obtain a stable product <85) It would appear that if the intermediate has the structure shown below, that a single closure would produce the endoperoxide directly ... 

The oxygen molecule, a paramagnetic species with an unpaired electron on each atom, has already been referred to as biradical, albeit an unreactive one. The photochemical excitation of an anthracene to a biradical, or to something rather like one, has also been mentioned (p. 331) if this excitation is carried out in the absence of air or oxygen, instead of the trans-annular peroxide—(104)—a photo-dimer (130) is obtained ... 

Shortly after mercury was accidentally introduced into a system containing a solution of anthracene in carbon disulfide under an atmosphere of oxygen, an explosion occurred. Presence of mercury may have catalysed rapid oxidation of carbon disulfide. 

According to the results of Ben Taarit and co-workers (76) and Neikam (77) Ce(III) Y zeolites will not form anthracene cation radicals but upon oxidation to Ce(IV) the radicals are readily formed. This experiment suggests that one role of oxygen during calcination may be to oxidize certain cations. The surface may be oxidized by molecules other than oxygen since the chlorination of 7-alumina by carbon tetrachloride considerably increases the sites responsible for the acceptor character. These sites, which oxidize perylene into the paramagnetic radical ion, have been attributed to biocoordinated positive aluminum atoms (78). 

Although organic anion radicals are oxygen sensitive, they have been isolated as crystalline salts from a variety of electron acceptors (e.g., chloranil, tetracyanoethylene, tetracyanoquinodimethane, perylene, naphthalene, anthracene, tetraphenylethylene, etc.) and their structures have been established by X-ray crystallography.180... 

A peculiar effect was observed in the decomposition of 19 a with anthracene as fluorescer when oxygen was carefully removed from the solutions an increase of the chemiluminescence decay rate and of the dioxetane cleavage resulted. It was suggested that this was due to a catalytic effect of triplet anthracene (formed by energy transfer from triplet formate) on the decomposition of the dioxetane. When oxygen is present, triplet anthracene is quenched. Whether such a catalytic effect of triplet anthracene or similar compounds on dioxetane cleavage actually exists has not yet been fully established positive effects were observed by M. M. Rauhut and coworkers 24> in oxalate chemiluminescence and by S. Mazur and C. S. Foote 80> in the chemiluminescent decomposition of tetramethoxy-dioxetane, where zinc tetraphenylporphy-rin seems to exert a catalytic effect. However, the decomposition of trimethyl dioxetane exhibits no fluorescer catalysis 78h... 

---