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Raman and resonance Raman spectroscopy with ultraviolet excitation were performed on several sample types of oilsands-derived bitumen, highly heterogeneous mixtures of hydrocarbons, and commercial gasoline samples. Only excitation wavelengths below ∼240 nm successfully yielded fluorescence-free Raman spectra on all of the samples tested. The spectra were surprisingly simple in the 800–1800 cm−1region, with most of the samples yielding spectra containing only 2 bands. The results presented here tentatively suggest that ultraviolet (UV) Raman spectroscopy in the “fingerprint” spectral regions will be useful for the qualitative identification of saturate, mono-, bi-, tri-, and polycyclic aromatic hydrocarbons. Tentative marker bands for total aromatic, saturate, mono-, and bicyclic (or higher) aromatic hydrocarbons are clearly observed at ∼1600, <900, 1036, and ∼1380 cm−1, respectively. Observed relative intensities vary with the excitation wavelength from 220 to 234 nm, suggesting that some selectivity is achievable by wavelength tuning. Preliminary investigations of commercial gasoline samples indicate that UV Raman spectroscopy can be used for refinery/vendor identification of unknown gasoline samples.

We have obtained a resonance Raman spectrum of the radical cation of promazine. We have also carried out density functional theory calculations to find the structures, hyperfine coupling constants (hfcc's), spin densities, and vibrational frequencies for the ground electronic states of the neutral chlorpromazine molecule and its radical cation. Preliminary vibrational assignments were made for all of the observed bands in the resonance Raman spectrum of the radical cation of chlorpromazine and in the FT-Raman spectrum of the neutral chlorpromazine molecule. Our results indicate that the radical cation of chlorpromazine has a nonplanar structure similar to that of the radical cation of promazine. However, the chlorine atom at the 2 position in chlorpromazine appears to noticeably change the hfcc's and spin densities of the radical cation compared to the radical cation of promazine. This is possibly due to conjugation and/or through-bond interactions of the chlorine atom with the central-ring heterocycle.

We present a resonance Raman spectrum of the radical cation of promazine. Density functional theory computations were used to find the structures, hyperfine coupling constants (hfcc's), spin densities, and vibrational frequencies for the ground electronic states of the neutral promazine molecule and its radical cation. Preliminary assignments for all of the observed Raman bands for the neutral promazine molecule and its radical cation are given. The density functional theory computed optimized structures show the S0 states of the neutral molecule (with a dihedral angle of 147.1°) and its radical cation (with a dihedral angle of 172.13°) are both nonplanar. The DFT-computed spin densities suggest the radical cation of promazine has significantly more spin density on nitrogen compared to sulfur, while the sulfur has a greater spin density than nitrogen in the radical cation of phenothiazine. The calculated HOMO and LUMO electron densities display noticeable differences in both the central ring and the side chain upon excitation. This appears consistent with the promazine radical cation experimental resonance Raman intensities.

(R)-(−)-1,1‘-Binaphthyl-2,2‘-diyl hydrogen phosphate (BiNPO4H) forms radical anions (λmax = 460 nm and ε460 = 8600 L mol^-1 cm^-1) on reaction with hydrated electrons. The radical anion undergoes acid-catalyzed protonation with a rate constant of (5.7 ± 0.9) × 10⁹ L mol^-1 s^-1 to form H-adduct, which has absorption at λmax = 410 nm. A similar adduct but having a slightly different absorption λmax = 405 nm (ε405 = 2900 L mol^-1 cm^-1) is formed on the addition of H atoms to BiNPO4H. Addition of OH^• radicals to BiNPO4^- also formed an adduct which absorbs at λmax = 405 nm (ε405 = 3100 L mol^-1 cm^-1). Oxidation of BiNPO4^- with strong oxidizing radicals such as SO4^•-, Tl²⁺ and Cl2^•- led to the formation of the radical cation. It is also formed by dehydroxylation of the OH-adduct in acidic solution. The radical cation has a broad absorption spectrum with peaks at 340, 405, 460, and 630 nm (ε630 = 2000 L mol^-1 cm^-1). It decays with a rate constant of 5 × 10⁴ s^-1. Reduction potentials of the radical cation and the anion of BiNPO4^- have been determined to be 1.70 and −1.51 V vs SHE at pH 9, respectively. The rate constants for electron transfer reactions of these radicals with a number of compounds have been determined as a function of their reduction potentials. The bimolecular rate constants obtained were fitted with the rates predicted by the classical Marcus electron transfer theory. A good free energy gap correlation (log k vs −ΔG) was obtained for the rate constants of reaction of ^-•BiNPO4^- with organic compounds. The rate constants of reactions of ^+•BiNPO4^- with inorganic anions also showed a good free energy gap correlation. But rate constants showed poor correlation with the nucleophilicity of the anion. This indicates that reaction between ^+•BiNPO4^- and inorganic anions is due to electron transfer and not a nucleophilic addition. This was further confirmed from the transient spectrum of the oxidized products formed in the reaction. In contrast to the reaction of the inorganic anions, the rate constants for reaction of ^+•BiNPO4^- with unsaturated compounds followed the rates predicted by Marcus theory only in the region of −ΔG > 0, and in the −ΔG &lt; 0 region the observed rates are higher than the predicted rates and the deviation from the predicted rate increases with decrease in −ΔG. This indicates that when the electron transfer reaction becomes endothermic, addition of the radical cation to the unsaturated compounds increasingly becomes the dominant pathway of the reaction.

Rate constants for the reactions of triplet decafluorobenzophenone (³DFB) with 30 alkenes have been measured, with values in the range 10⁷−10⁹ L mol^-1 s^-1. The rate constant increases upon substituting electron-donating groups on the double bond, whereas it decreases upon substituting electron-withdrawing groups. For cyclohexene and 2-butene, the rate constant increases with increasing methyl substitution at the double bond, suggesting that steric effects play a minor role in the reaction. Further, there is a linear correlation between log kr (kr = the second-order rate constant of the reaction of³DFB and alkene) and the ionization potential of the alkene. The extent of hydrogen abstraction was determined by measuring the yield of the ketyl radical. Quantum yields for ketyl radical formation, ΦK, increase with the ionization potential and the number of activated hydrogens, nH, on the alkene. The absolute values of ΦK and a linear correlation between ΦK/nH and ionization potential suggest that hydrogen abstraction is preceded by complex formation.