Anthracene pulse radiolysis

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... 

A third important reaction of aromatic radical-cations is carbon-carbon bond formation with a further aromatic substrate. This reaction is limited to the oxidation in acetonitrile of substrates with electrondonating substituents. Radical-cations from benzene, naphthalene and anthracene form a-complexes but do not form a a-bonded reaction intermediate. Tlie dimerization reaction has been investigated both by pulse-radiolysis [22] in water and by electrochemical methods [27] in acetoni-... 

Rate constants for the protonation of radical-anions in dimethylformamide by added phenol can be determined by electrochemical techniques [8], Pulse radiolysis methods have been used to measure the rate constants in an alcohol solvent. This technique generates the radical-anion on a very short time scale and uv-spectroscopy is then be used to follow the protonation of this species to give the neutral radical with different uv-absorption characteristics [9]. In the case of anthracene, the protonation rate is 5 x 10 M" s with phenol in dimethylformamide and 5 x 10 s in neat isopropanol. Protonation by hydrogen ions approaches the diflusion-controlled limit with a rate constant of 10 M s in ethanol [9]. 

Similarly, fluorescence detected magnetic resonance effects observed during the pulse radiolysis of anthracene-dio in the presence of 2,3-dimethyl-l-butene support the presence of 8 equivalent methyl groups. Because the splitting, Odi = 0.82 mT, was approximately one-half that of the monomer splitting, Omon =1.71 mT, the sandwich dimer 91 + was invoked. ... 

Chemical evidence for the existence of electrons in irradiated cyclohexane was obtained from pulse radiolysis studies of solutions containing aromatic solutes27. Because of the lifetime of the pulse these experiments only allowed the determination of ions still surviving after 10 6 sec. With benzophenone and anthracene as scavengers transient absorption peaks at 700 nm and 730 nm respectively, were obtained. These were consistent with the known spectra of the benzophenone and anthracene radical ions and are most simply accounted for by assuming direct electron capture by these solutes. Positively charged ion radicals may also be produced since these are likely to have similar spectra. Ion yields can be calculated since the absorption coefficients are known, but these yields necessarily represent the sum of the positive and negative ion yields. Some results are shown in Fig. 3. 

Fluorescence detected magnetic resonance effects observed during the pulse radiolysis of anthracene-d10 in the presence of tetramethylethene portray an additional facet of the cyclobutane radical cation system [345, 346]. The spectra [eight ( ) equivalent methyl groups, ad = 8.2 G approximately one half of the monomer splitting, am = 17.1 G] are compatible with a dimer cation. In analogy to the benzene dimer radical cation [347, 348] they were interpreted as evidence for a sandwich , one molecule above the other [346],... 

Sens, (pulse radiolysis of benzene energy transfer to naphthalene, anthracene, benzophenone, benzil) Determination of energy transfer efficiencies 369... 

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]. 

Figure 1. Absorption spectra of aromatic anions in ethyl alcohol, formed by electron attachment in pulse radiolysis, (a) Diphenyl in ethyl alcohol. The solid curve was obtained during the pulse. The dashed curve was obtained after a delay of 12 sec. and is thought to be the adduct radical Ci2Hu. (b) Anthracene in ethyl alcohol. This band of the anthracenide ion was observed spectrophotometrically at about 0.2 yjsec. after the pulse, (c) p-Terphenylide ion in solutions of p-terphenyl in ethyl alcohol. Spectra are...

Some evidence, in pulse radiolysis, has been obtained (6, 35) for the formation of the cation of diphenyl, p-terphenyl, anthracene, and trans-stilbene in dichloroethane and other chlorinated solvents, and for the p-terphenyl cation in chloroform (6). Some of these cation spectra are shown in Figure 2. The diphenyl solution shows absorption band at 690 m/a and 380 m/m. The diphenylide anion bands in the alcohols and in ethers are at 630 mp and 405 m/, so that the cation bands seem to be distinguishable. Anthracene in dichloroethane shows a band at 430 m/, ... 

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 nanosecond pulse radiolysis technique has been described (8, 14). Carbon tetrachloride was purified as follows Matheson Research grade CC14 was dried over anhydrous potassium carbonate for several days, and subsequently distilled, discarding initial and final fractions. However, untreated research grade CCLj gave identical results to that treated as above. Zone refined naphthalene, anthracene, biphenyl, and N,N,N, N -tetramethyl-paraphenylenediamine (TMPD) were used pyrene, 1 2 benzanthracene were recrystallized from absolute alcohol, and aniline was purified as described in an earlier paper (6). Normal hexane, cyclohexane, 3-methylpentane, benzene, and toluene were Matheson research grade methanol and ethyl alcohol were analytical grade. 

C [O2] adjusted to agree with ref. 16 anthracene-sensitized, pulse radiolysis. 

Hunt, J.W. and Thomas, J.K., Pulse radiolysis studies of the formation of triplet excited states in cyclohexane solutions of naphthalene and anthracene,/. Chem. Phys., 46, 2954,1967. 

Adam, W., Schneider, K., Stapper, M., and Steenken, S., Multiple-photon chemistry of 9-(phe-noxymethyl)- and 9,10-bis(phenoxymethyl)anthracenes in the laser-jet generation, photochemistry and time-resolved laser-flash spectroscopy of anthracenyl radicals and pulse radiolysis of 9-(bromomethyl)anthracene,/. Am. Chem. Soc, 119, 3280-3287, 1997. 

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