Anthracene ions

Accordingly, HMO theory predicts that the half-wave potential and the HFSC of the anthryl protons should approach those of the unsubstituted anthracene ions when substitution causes 0 to approach 90°. But for smaller val-... 

ESR signal that was found to be due to unreacted initiator. The signal was a function of the charged ratio M/I. Sodium-biphenyl was found to be more reactive than the naphthalene and anthracene ion-radicals. Therefore, some step of the initiation was slow and had an energy of activation higher than that for propagation. The authors postulated that the dimerization of the radicals and the addition of the first monomer unit was involved in the slow step. They explained their results on the following basis ... 

B. D. McNicol (Koninklijke/Shell Laboratorium, Amsterdam, Netherlands) With reference to Figure 1 of your paper regarding the spin concentration of positive anthracene ions, you state that rehydration results in a large decrease in spin concentration. This is certainly not apparent in the figure. Also, were no measurements made on rehydrated samples which had been activated above 550°C This would shed some light on the reason for the decrease in spin concentration observed above 550°C. In the absence of x-ray or other evidence, this decrease may not be due to structure collapse. 

Comparison of Measured and Calculated Ion Lifetimes. The yield of biphenyl or anthracene ions in cyclohexane, observed by pulse-radiolysis-absorption-spectroscopy, was 10%-20% greater at a few tenths of a microsecond than it was at 2-3 microseconds (II). Each of these solutes captures both positive and negative charges, so in each case the observed neutralization reaction was... 

The decrease in ionization energy in solution is due to the effect of I1 which is always greater than I Vq I. If the same solute is measured in different hydrocarbons, approximately the same polarization energy should result, since is approximately 2 for most of the hydrocarbons. In Table 5, the polarization energies of the positive anthracene ion in three different solvents are given. A value of -1.06 eV is obtained for all three solvents which is an indication that the anion radius is constant, since Er is approximately the same for the three liquids. 

Some information is available about the nitration of polycyclic hydrocarbons and their derivatives, but it is of no quantitative significance. The formation of a cr-complex from anthracene and nitronium ions has been mentioned ( 6.2.3, 6-3)-... 

Tetramethyl-l,2-oxathietane (138) was prepared by diazotization of 139, which was prepared from the aziridine (140) (86JA3811).Tlie reaction presumably involves the decomposition of the sulfonium ion intermediate (141).Tire dichloromethane solution of 138 at -20°C is sufficiently stable to permit exploration of the chemical reactions. Tire oxathietane 138 undergoes a formal [[Pg.248]

In the context of this section it is important that Ruchardt and Tan (1970 a) found that (solid) benzenediazonium fluoroborate gave benzyne adducts with potassium acetate in the presence of aryne trapping agents such as tetracyclone or anthracene. This is, however, not the case if water is present (Cadogan, 1971). As a consequence of these observations, Cadogan et al. (1971) simplified the formation of arynes from diazonium ions by converting aniline or its substitution products into arynes in a... 

The evaluation of polarographic redox potentials of anthracene- and phenanthrenediazonium ions indicates, however, that the charge delocalization into these aromatic rings may be smaller (Elofson et al., 1984 b). 

Androcymbine, O-benzyl-, synthesis 282 Anilinium ion, as nucleophilic partner 49 f. Anthracene, trapping of arynes 187f. Antimony-de-diazoniation 275 Arenediazonium ions... 

Hayon23 studied the yields of ions and excited states in pulse radiolysis of liquid DMSO using anthracene as a solute to determine the yield of free ions and naphthalene as a solute to measure the yield of triplet excited states. Anthracene is known to react with solvated electrons to give the anthracene radical anion, A T... 

Chromatograms demonstrating the simultaneous use of all three detector functions are shown in figure 22. It is seen that the anthracene is clearly picked out from the mixture of aromatics by the fluorescence detector and the chloride ion, not shown at all by the UV adsorption or fluorescence detectors, clearly shown by the electrical conductivity detector. 

DP) and leads (Equation 4.5) to the formation of an anthracene cation radical as a result of the single-electron transfer process. The resulting ion-radical pair [AN, DP is the critical intermediate that subsequently evolves to cycloadduct (AD). 

In fused ring systems, the positions are not equivalent and there is usually a preferred orientation even in the unsubstituted hydrocarbon. The preferred positions may often by predicted as for benzene rings. Thus it is possible to draw more canonical forms for the arenium ion when naphthalene is attacked at the a position than when it is attacked at the p position, and the a position is the preferred site of attack,though, as previously mentioned (p. 682), the isomer formed by substitution at the p position is thermodynamically more stable and is the product if the reaction is reversible and equilibrium is reached. Because of the more extensive delocalization of charges in the corresponding arenium ions, naphthalene is more reactive than benzene and substitution is faster at both positions. Similarly, anthracene, phenanthrene, and other fused polycyclic aromatic hydrocarbons are also substituted faster than benzene. 

The oxidation of an anthracene suspension in sulfuric acid conducted in the presence of cerium salts can serve as an example of mediated oxidation. In the bulk solution the Ce" ions chemically oxidize anthracene to anthraquinone. The resulting Ce ions are then reoxided at the anode to Ce". Thus, the net result of the electrochemical reaction is the oxidation of anthracene, even though the electrochemical steps themselves involve only cerium ions, not anthracene. Since the cerium ions are regenerated continuously, a small amount will suffice to oxidize large amounts of anthracene. 

The HO—LU interaction came early to the notice of theoreticians. Hiickel 74> pointed out the role of LU in the alkaline reduction of naphthalene and anthracene. Moffitt 75> characterized the formation of S03, SO2CI2, etc. by the reactions of SO2 as an electron donor with the S-atom-localiz-ing character of HO MO. Walsh 76) considered that the empirical result of producing nitro compounds in the reaction of the nitrite anion with the carbonium ion should be attributed to the HO of the NO2 anion which is localized at the nitrogen atom. 

The energy available from the anthracene triplet (42 kcal/mole) is sufficient to produce either of these states. The singlet excited molecule subsequently attacks a ground state anthracene to produce the observed endoperoxide. The 1Aff state is believed to be responsible for the addition to anthracene to form the endoperoxide since it closely resembles a diradical species, while the 1Ss+ state more closely resembles a dipolar ion. 

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). 

With many aromatic hydrocarbons as solutes, excited state yields in alkane solutions are nearly equally divided between singlets and triplets, and these yields increase with solute concentration until -0.1 M (Salmon, 1976 Thomas et al., 1968). In these systems, both the solute anion and the solute excited state yields increase similarly with solute concentration. With anthracene as a solute, the rate of growth of anthracene triplet matches that of the decay of the anthracene anion. With aromatic solvents, on the other hand, solute ions play... 

Compounds of this type may only be isolated in the presence of suitable donor molecules, among those, diglyme has been used frequently, but other examples include TMEDA or 2,2,1-crypt for sodium.150 The reduction of naphthalene or anthracene with sodium in diglyme affords separated ions with the radical anion [Na(diglyme)2][naphthalene/anthracene] 139, 140.151... 

Time-resolved spectroscopy establishes that the fluorescence of the excited (singlet) anthracene ( ANT ) is readily quenched by maleic anhydride (MA), which leads to the formation of the ion pair ANT+, MA via diffusional electron transfer (see Fig. 12), i.e.,... 

Electron-transfer activation. Time-resolved spectroscopy establishes that irradiation of the charge-transfer band (hvCj) of various arene/0s04 complexes directly leads to the contact ion pair. For example, 25-ps laser excitation of the [anthracene, 0s04] charge-transfer complex results in the ion-radical pair instantaneously, as shown in Fig. 14218 (equation 76). 

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