The azide ion is a strong physical quencher of singlet molecular oxygen (1O2) and is frequently employed to show involvement of 1O2 in oxidation processes. Rate constants (k(q)) for the quenching of 1O2 by azide are routinely used as standards to calculate k(q) values for quenching by other substrates. We have measured k(q) for azide in solvent mixtures containing deuterium oxide (D2O), acetonitrile (MeCN), 1,4-dioxane, ethanol (EtOH), propylene carbonate (PC), or ethylene carbonate (EC), mixtures commonly used for many experimental studies. The rate constants were calculated directly from 1O2 phosphorescence lifetimes observed after laser pulse excitation of rose bengal (RB), used to generate 1O2. In aqueous mixtures with MeCN and carbonates, the rate constant increased nonlinearly with increasing volume of organic solvent in the mixtures. k(q) was 4.78 x 10(8) M(-1) s(-1) in D2O and increased to 26.7 x 10(8) and 27.7 x 10(8) M(-1) s(-1) in 96% MeCN and 97.7% EC/PC, respectively. However, in EtOH/D2O mixtures, k(q) decreased with increasing alcohol concentration. This shows that a higher solvent polarity increases the quenching efficiency, which is unexpectedly decreased by the proticity of aqueous and alcohol solvent mixtures. The rate constant values increased with increasing temperature, yielding a quenching activation energy of 11.3 kJ mol(-1) in D2O. Our results show that rate constants in most solvent mixtures cannot be derived reliably from k(q) values measured in pure solvents by using a simple additivity rule. We have measured the rate constants with high accuracy, and they may serve as a reliable reference to calculate unknown k(q) values.

The azide ion is a strong physical quencher of singlet molecular oxygen (1O2) and is frequently employed to show involvement of 1O2 in oxidation processes. Rate constants (kq) for the quenching of 1O2 by azide are routinely used as standards to calculate kq values for quenching by other substrates. We have measured kq for azide in solvent mixtures containing deuterium oxide (D2O), acetonitrile (MeCN), 1,4‐dioxane, ethanol (EtOH), propylene carbonate (PC), or ethylene carbonate (EC), mixtures commonly used for many experimental studies. The rate constants were calculated directly from 1O2 phosphorescence lifetimes observed after laser pulse excitation of rose bengal (RB), used to generate 1O2. In aqueous mixtures with MeCN and carbonates, the rate constant increased nonlinearly with increasing volume of organic solvent in the mixtures. kq was 4.78 × 108M−1 s−1 in D2O and increased to 26.7 × 108 and 27.7 × 108M−1 s−1 in 96% MeCN and 97.7% EC/PC, respectively. However, in EtOH/D2O mixtures, kq decreased with increasing alcohol concentration. This shows that a higher solvent polarity increases the quenching efficiency, which is unexpectedly decreased by the proticity of aqueous and alcohol solvent mixtures. The rate constant values increased with increasing temperature, yielding a quenching activation energy of 11.3 kJ mol−1 in D2O. Our results show that rate constants in most solvent mixtures cannot be derived reliably from kq values measured in pure solvents by using a simple additivity rule. We have measured the rate constants with high accuracy, and they may serve as a reliable reference to calculate unknown kq values.

Hexafluoroacetone was cophotolyzed with acetone and with acetone-dg, and the rate of the unimolecular dehydrofluorination of the 1,1,1-trifluoroethanes formed from combination of CFg and CHg or CDs radicals was determined from the difluoroethene/trifluoroethane ratio. This ratio was found to depend on the extent of conversion because of secondary reactions. Extrapolations to zero conversion corrected for this effect. The measured kinetic isotope effect was found to be 2.84 ± 0.07. Values of the isotope effect and rate constants predicted by applying RRKM theory to two different models of• the activated complex show that both models predict results similar to observations.

heavy type and are wisely repeated as necessary rather than being replaced by references to a previous mention of the hazard. The IR and proton NMR spectra of the products are depicted. T1.C is often used, but GLC is not. A number of the experiments use phase transfer catalysis. Some of the syntheses areof common substances such asaspirin, phenacetin, and DEET. There are a couple of isolation experiments-caffeine from tea leaves and eugenol from clovesbut no experiments on kinetics, polymers, carbohydrates, or amino acids. Questions and exercises are found at the end of each chapter.Part I11 (161 pp.) coven the qualitative analysis of the main organic functional groups. Several new classification tests utilizing phase-transfer catalysis are employed as is spectroscopic confirmation of structure. Forty-seven pages of derivative tables are in Part Ill. 1 believe the authors should have omitted the IXototization of Primary Amines (p. 542) from their procedures. Carcinogenic nitrosamines, which are not mentioned in the text, might he formed from secondary amine contaminants o r by misapplication of the test to a secondary amine.Durst and Gokel have written a first rate, modern laharatory text which gives today's safety conscious instructor a large number of experiments to chwse from and allows him to incorporate qualitative organic analysis into the laboratory without requiring purchase of an additional text.

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