9,10-Dimethylanthracene, pyrene

Figure 2. Gas chromatogram of A, PAH fraction of diesel particulate extract (Sl-C2) and By its HPLC subfraction C (S1-C2). GC conditions 45- X 0.35-mm id SE54 glass capillary column flame ionization detector temperature, 110°C for 2 min, programmed to 170°C at 10°/min, to 212°C at 3°/min, to 278°C at 8°/min. Peak identities 1, phenanthrene 2, anthracene 3-6, methylanthracene/-phenan-threne 7, 2-phenylnaphthalene 8-10, dimethylanthracene/-phenanthrene 11, fluoranthene 12, aceanthrylene/acephenanthrylene 13, pyrene 14-15, trimethylan-thracene/-phenanthrene 16, benzo [ghi]fluoranthene 17, benzo[a/anthracene 18, triphenylene 19, chrysene 20, benzo[b]fluoranthene 21, benzo[]]fluoranthene ...

The radiation chemistry of 2-propanol is analogous to that of methanol, that is, the main reactive species are Cs and (CH3)2 COH. In alkaline solution, (CH3)2 COH deprotonates to (CH3)2CO . In the presence of N2O or acetone, es is converted to (CH3)2 C0H/(CH3)2C0 by the reactions in Eqs. 30 and 18, or the reaction of Eq. 20, respectively. The solvated electron in 2-propanol has been utilized to study electron-transfer reactions between aromatic radical anions (donor) and aromatic molecules (acceptor) [16]. The donor-acceptor pairs studied were pyrene-anthracene, pyrene-9,10-dimethylanthracene and w-terphenyl-/ -terphenyl. In the first two cases an equilibrium was established and the parameters forward and kback were measured this was the first example of the measurement of an equilibrium constant by use of pulse radiolysis. The rate constants for the electron-transfer reactions were examined in terms of the Marcus theory [17]. 

For example, simple fluorescence intensity measurements on dispersed hydrocarbon probes such as anthracene [17], perylene [18], pyrene [6,17,22], 9,10-dimethylanthracene (DMA) [60], and coumarin dyes [62] have confirmed that PMAA displays pH-dependent solution behavior. A marked decrease in the intensity of the probe occurs between pH 5 and 6, which coincides with the conformational transition of PMAA as determined by classical methods [2-4,47-50]. Two interrelated effects account for this behavior the solubilizing capacity of the polymer promotes an increase in the concentration of the probe in the solution [6,17,18,60,62] and because the intensity of the fluorescence observed is proportional to the excited state population the resulting emission is enhanced. The hydrocarbons may also be considered to be preferentially solubilized within the hydrophobic domains or structures of the hypercoiled state [6,22]. This results in a degree of protection from the deactivating effects of the aqueous phase and a concomitant increase in the fluorescence observed [6,17,18,22,60,62]. 

The reactions were carried out in isopropyl alcohol. This compound was selected as solvent because the natural lifetime of the aromatic radical anion with respect to protonation (1, 3) is longer than in methyl alcohol or ethyl alcohol. The isopropyl alcohol was obtained from Mathe-son, Coleman, and Bell and was freshly distilled over sodium metal through a glass-packed column for each set of runs. Anthracene from Matheson, Coleman and Bell, pyrene from Aldrich Chemical Co., m-terphenyl and p-terphenyl from City Chemical Corp. were purified as described (2). 9,10-Dimethylanthracene obtained from K and K Laboratories, Plainview, N. Y., was recrystallized from isopropyl alcohol solution. 

The donor-acceptor pairs investigated were pyrene-anthrace, pyrene-9, 10-dimethylanthracene and m-terphenyl-p-terphenyl. The radical anions of these compounds may be observed at the appropriate optical absorption bands, the maxima of which are as follows m-terphenyl, 7400 A., a broad weak band p-terphenyl, 8770 A. pyrene, 4900 A. anthracene, 7200 A. and 9,10-dimethylanthracene, 7300 A. For most of the systems we have studied in this and earlier work (1, 2, 3) these absorption bands have been known (4, 6, 8) from work on solutions in which the radical anions are stable. In the systems involving pyrenide anion as donor the decay of the donor anion and the formation of the acceptor could be observed simultaneously since their absorption bands do not overlap extensively. 

Figure 2. Plot of kia[Ab] + b[Ai] > from decay curves of pyrenide anion, against concentration of 9,10-dimethylanthracene. The concentration of pyrene is constant and is equal to 1.1 X 10r2 M. The slope gives kia = 1.3 X 109M" seer1 at 25°C.

The value of De, in Equation 8, is taken from the almost horizontal portion of the rate curve, which represents the attainment of equilibrium between the two radical anions, at the region in which the fast portion of the decay curve becomes asymptotic to this horizontal. Such a rate curve, taken at two different sweep times, is shown in Figure 3. The uncertainty in the value of De is very small since the linear portion of the curve is nearly horizontal. This linear portion is not perfectly horizontal when examined on a long time-scale simply because the rates of Reactions 2 and 3 are not completely negligible. Another observation which is indicative of the establishment of equilibrium with respect to Reaction 4 may be made in the following way. If one observes the slow decay of the two radical anions at their respective wavelengths, which in the system pyrene-anthracene would be 490 m/u, for the former and 720 m/u, for the latter, both anion spectra are found to be present for many tens of microseconds. Moreover, the ratio of the optical densities at these two wavelengths remains constant over this extended period. The same is found for pyrene-dimethylanthracene. 

Equilibrium Constant. For those cases in which the electron transfer equilibrium is overwhelmingly on the side of the acceptor anion, the rate of the back reaction, as has been pointed out (2), is negligible. In some cases where this is not true, as for diphenyl-naphthalene, the equilibrium with respect to Reaction 4 may be quenched by the protonation of the acceptor anion in Reaction 2. In the case of pyrene-anthracene and pyrene-9,10-dimethylanthracene, where equilibration occurs, the back reaction has a measurable effect upon the electron transfer kinetics, and k4b has been determined. From these data, the equilibrium constant may also be reliably estimated since it is given by the ratio Kc = k4a/k4b. The values obtained at 25°C. are (1) pyrene-anthracene —86 and (2) pyrene-9,10-dimethylanthracene —35. These values for Kc may also be determined from the difference in the reduction potentials of the pair as measured potentiometrically (5, 8, 9, 18). The equilibrium constant is related to the reduction potential difference, AF, by ... 

Reduction of arenes by A1 in ionic liquids is efficient. For example, pyrene is fully saturated (84% yield) and 9,10-dimethylanthracene gives the 9,10-dihydro derivative (81%). ... 

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