A. M. Nazarov

Determination of the Absolute Rate Constants of Reactions between Diphenyl Carbonyl Oxide and Alcohols by Flash Photolysis

The rate constants of the reactions of diphenyl carbonyl oxide Ph2COO with a number of alcohols and water in acetonitrile, benzene, andn-decane solutions (295 K) were measured by flash photolysis. The rate constants vary over a range from 400 (triphenylmethanol in a MeCN solution) to 2.5 × 105 l mol–1 s–1 (adamantanol in a benzene solution). α-Methoxydiphenylmethyl hydroperoxide is the reaction product of Ph2COO and MeOH. The absence of a kinetic isotope effect and the dependence of the logarithms of the rate constants on the first ionization potentials of alcohols are indicative of the formation of a C–O bond at the rate-limiting step of the reaction.

Rate constants for the reaction of diphenyl carbonyl oxide with phenols

The kinetics of the reaction of diphenyl carbonyl oxide Ph2COO with o- and p-substituted phenols is studied by pulse photolysis and high-speed spectrophotometry. The rate constant strongly depends on the phenol structure and ranges from 1.3 × 103 for ionol to 2.1 × 108 l mol–1 s–1 for o-aminolphenol. A U-shaped curve illustrating how the logarithm of the rate constant changes with a change in the Hammett constants (σ0) of the substituents in the aromatic ring is found for the studied compounds. Possible pathways for the reaction of Ph2COO with phenols are discussed.

Electronic effects in the reaction of diphenylcarbonyl oxide with aldehydes

The reactivity of 14 aldehydes with diphenylcarbonyl oxide Ph2COO was characterized by thek33/k31 ratio. The values ofk33/k31 vary from 1.3·10−2 (C6F5CHO) to 1.0 (p-Me2N-PhCHO), 70 °C, acetonitrile as the solvent. A charge transfer complex (CTC) was suggested to be primarily formed during the reaction. The electronic effects of substituents in the reaction were analyzed using the published data. Carbonyl oxide reacts with aldehydes as a nucleophile (at the carbon atom of the −CHO fragment to form 1,2,4-trioxolane) and also as an electrophile (at the aromatic ring with the intermediate formation of CTC). The latter is transformed into either 1,2,4-trioxolane or the products of oxidation of the phenyl ring.

Absolute rate constants of decay of aryl-substituted carbonyl oxides

The decay kinetics of a series of carbonyl oxides (CbO)—4-methylbenzophenone oxide, 2,5-dimethylbenzophenone oxide, 4-chlorobenzophenone oxide, 2-bromobenzophenone oxide, and acetophenone oxide—were studied by the pulse photolysis technique in acetonitrile, benzene,n-decane, andn-pentane. The absorption spectra were studied, and the absorption coefficients and absolute rate constants of CbO decay were determined. The absorption maxima observed in the spectra of carbonyl oxides range within 405±25 nm. The decay rate constant was found to depend on both the CbO structure and the medium.

Thermal decomposition of diazocompounds in aerated solutions. Possible realization of a quantum-chain process

Thermal decomposition (85°Ñ,o-C6H4Cl2, O2) of RN2 diazocompounds (R−Ph2C (I),p-Cl−Ph(ph)C (II), (p-Me2N−Ph)2C (III), Me(Ph)C (IV), fluorenylidene Fl (V), adamantylidene Ad (VI) is accompanied with chemiluminescence (CL) in the visible region of spectrum. The effect of experimental conditions on CL intensity was studied, as well as the decomposition kinetics of RN2. In (IV) the rate constant of the process was found to depend on the initial concentration of RN2, which is caused by quantum-chain consumption of the diazocompound.

Quantitative description of the effect of solvent on kinetics of benzophenone oxide decay

The effect of solvent on rate constants of benzophenone oxide decay was investigated by flash photolysis. A quantitative description of this dependence in the terms of the Koppel-Palm equation suggests that all types of the solvation (non-specific electrostatic and polarizational, specific electrophilic and nucleophilic) strongly affect the reactivity of benzophenone oxide. Besides, strengthening of any effect leads to a decrease of the observed rate constant.

Electronic structure of aryl- and carbonyl-containing diazomethane derivatives, as disclosed by photoelectron spectroscopy

Vertical ionization energies (IE) of aryl and carbonyl derivatives of diazomethane have been determined by photoelectron spectroscopy. The types of the highest occupied molecular orbitals (HOMO) in these molecules are identified.

Kinetics, mechanism, and products of the reaction of diphenylcarbonyl oxide with carboxylic acids

The kinetics of the reactions of acetic, benzoic, formic, oxalic, malic, tartaric, trifluoroacetic, and hydrochloric acids with diphenylcarbonyl oxide Ph2COO was studied. The carbonyl oxide Ph2COO was generated by flash photolysis of diphenyldiazomethane Ph2CN2 in solutions of acetonitrile and benzene at 295 K. The apparent rate constants of the reaction range from 4.6·108 for (COOH)2 in MeCN to 7.5·109 L mol–1 s–1 for acetic acid in a benzene solution. The reaction mechanism was proposed, according to which at the first stage the carbonyl oxide is reversibly solvated by the solvent. Then the solvated carbonyl oxide reacts with the acid molecule by the mechanism of insertion at the O—H bond.

Flash Photolysis of Diphenyldiazomethane in the Presence of Organic Sulfides

The flash photolysis of diphenyldiazomethane in acetonitrile, benzene, and n-decane solutions saturated with air resulted in the formation of diphenyl carbonyl oxide Ph2COO which decayed in combination reactions. In the presence of organic sulfides, the transfer of the terminal oxygen atom of Ph2COO to the sulfur atom was observed. The kinetics of this reaction was studied. The absolute rate constants (k6, dm3 mol–1 s–1) of the reactions of Ph2COO with sulfides at 295 K (acetonitrile as a solvent) varied from 4.1 × 102 (Me2S) to 8.1 × 104 (Ph2S). The solvent effect on the reaction kinetics and product composition was studied. The mechanism of the process was discussed.

Solvent effects on the absorption spectrum and recombination kinetics of diphenylcarbonyl oxide

The absorption spectra and rate constants of diphenylcarbonyl oxide recombination in a series of solvents and their binary mixtures were determined by flash photolysis. An increase in the solvent polarity causes hypsochromic shift of the maximum in the absorption spectrum of Ph2COO. The analysis of the solvent effect on the recombination rate constant in terms of the four-parameter Koppel—Palm equation shows that the reactivity of carbonyl oxide depends on both specific and non-specific solvations. Quantum chemical B3LYP/6-31G(d) calculations of H2COO and PhHCOO carbonyl oxides as well as the complexes of H2COO with acetonitrile and ethylene in different media were performed using a polarized continuum model.