The atmospheric oxidation of ethyl formate and ethyl acetate over a range of temperatures and oxygen partial pressures

The Cl‐atom‐initiated oxidation of two esters, ethyl formate [HC(O)OCH₂CH₃] and ethyl acetate [CH₃C(O)OCH₂CH₃], has been studied at pressures close to 1 atm as a function of temperature (249–325 K) and O₂ partial pressure (50–700 Torr), using an environmental chamber technique. In both cases, Cl‐atom attack at the CH₂ group is most important, leading in part to the formation of radicals of the type RC(O)OCH(O^?)CH₃ [R = H, CH₃]. The atmospheric fate of these radicals involves competition between reaction with O₂ to produce an anhydride compound, RC(O)OC(O)CH₃, and the so‐called α‐ester rearrangement that produces an organic acid, RC(O)OH, and an acetyl radical, CH₃C(O). For both species studied, the α‐ester rearrangement is found to dominate in air at 1 atm and 298 K. Barriers to the rearrangement of 7.7 ± 1.5 and 8.4 ± 1.5 kcal/mole are estimated for CH₃C(O)OCH(O^?)CH₃ and HC(O)OCH(O^?)CH₃, respectively, leading to increased occurrence of the O₂ reaction at reduced temperature. The data are combined with those obtained from similar studies of other simple esters to provide a correlation between the rate of occurrence of the α‐ester rearrangement and the structure of the reacting radical. © 2010 Wiley Periodicals, Inc. Int J Chem Kinet 42: 397–413, 2010     

Kinetic regularities in reaction of methanethiol with methanol

The kinetics of the reaction of methanethiol with methanol has been studied under gradientless conditions. A mechanism is postulated according to which, under the effect of methanol the surface is rapidly methoxylated and then CH₃O groups react with methanethiol or methanol to produce dimethyl sulfide and dimethyl ether. The kinetic equations obtained describe fairly well the reaction on the inhomogeneous catalyst surface.

---

. , CH₃O , . , .

     

Liquid-phase oxidation of bromovinyl compounds with molecular oxygen

Liquid-phase oxidation of bromovinyl compounds with the aim to obtain the corresponding α-bromo acids was studied. Original Russian Text R.B. Bayatyan, B.E. Bayatyan, L.A. Saakyan, 2006, published in Zhurnal Prikladnoi Khimii, 2006, Vol. 79, No. 11, pp. 1870–1873.     

Efficient heterogeneous oxidation of alkylarenes with molecular oxygen

[reaction: see text] Ru(OH)x/Al2O3 efficiently catalyzes the heterogeneous aerobic oxygenation or oxidative dehydrogenation of alkylarenes to give the corresponding oxygenated or dehydrogenated products. Catalyst/product separation is very easy, and the recovered catalyst is reusable with retention of the high catalytic performance.     

乙基橙-溴酸钾体系动力学光度法测定痕量甲醛

研究了在稀H2SO4介质中,痕量甲醛催化KBrO3氧化乙基橙褪色反应的适宜条件和影响因素,建立了测定痕量甲醛的动力学光度法。方法采用固定时间法于507 nm波长处测量体系的吸光度,在适宜条件下,ΔA与甲醛质量浓度具有良好的线性关系,方法的线性范围为0~0.24 mg/L,检出限为0.004 mg/L。该方法用于饮料、废水和废气中痕量甲醛的测定,测定结果的相对标准偏差RSD≤3%(n=6),回收率为102%。     

Kinetic regularities of micellar catalysis in the dephosphorylation with peroxide anion

The acid-base equilibrium of hydrogen peroxide in water solutions of cetyltrimethylammonium bromideand the reactivity of hydroxide and peroxide anions with respect to 4-nitrophenyl diethyl phosphate were investigated. In the micelles the acid ionization constant of the hydrogen peroxide increased three-fold. The application of the pseudophase distribution model under the conditions of competitive sorption of HO⁻ and HOO⁻ anions with the micelles of cetyltrimethylammonium bromide to the estimation of the main kinetic parameters of the micellar process was tested.     

Complexes of N-hydroxyphthalimide and cobalt(II) acetate in reactions of alkylarene oxidation by molecular oxygen

The synergetic effect of the catalytic system cobalt(II) acetate-N-hydroxyphthalimide (NHPI) was studied in acetic acid during the oxidation of alkylbenzenes. The formation of complex between the components of catalytic system NHPI and Co(II) was demonstrated with the use of 1H NMR spectroscopy. It was established that N-hydroxyphthalimide is included in the complex as a ligand substituting for acetic acid in the internal coordination sphere of the metal; the reaction of NHPI with cobalt ions in the internal sphere leads to the formation of phthalimide-N-oxyl radicals that than participate in the catalytic cycle of the oxidation of organic substrates. The stability constants of complexes of NHPI with cobalt acetate were determined, as were those for the outer-sphere complexes of alkylbenzenes with metallocomplex.     

Kinetic regularities of the reaction of dimethyldioxirane with cyclic acetals

Kinetic regularities of the reactions of dimethyldioxirane (1) with 1,3-dioxolane, 2-propyl-1,3-dioxolane, 2-i-propyl-1,3-dioxolane, 2-phenyl-1,3-dioxolane, and 2,2-pentame-thylene-1,3-dioxolane (RH) in acetone have been studied spectrophotometrically in the temperature range from 15 to 48°C. The reaction rate d[1] /dt=k[1]·[RH] does not depend on the oxygen concentration in the reaction mixture. The activation parameters in the reaction with 1,3-dioxolane have been determined: lgk=(5.13±0.6)−(10.07±0.82)/Q, where Q=2,303 RT kcal/mol.     

Catalytic oxidation of p-xylene with molecular oxygen in the presence of N-hydroxyphthalimide

Relationships of p-xylene oxidation in the presence of N-hydroxyphthalimide and Co(II) and Mn(II) salts were studied. The activity of the catalytic system strongly depends on the volume of the ligand incorporated in the salt. The synergism in combined use of Co(II) and Mn(II) salts is observed only in the step of p-toluic acid oxidation, whereas replacement of a half of the Co(II) salt by the Mn(II) salt in p-xylene oxidation leads to additive increase in the reaction rate.     

Chemiluminescence in the oxidation of cyclooctene by molecular oxygen

Chemiluminescence kinetics have been examined for the oxidation of cyclooctene by molecular oxygen. State University “L'vivs'ka Politekhnika,” 12 ul. S. Bandery, L'vov-13 290646, Ukraine. Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 35, No. 6, pp. 354–356, November–December, 1999     

Mechanism of initiation of the radical chain oxidation by molecular oxygen of hydroxymethylferrocene and its ethyl ether in organic solvents

Autooxidation of ethoxymethylferrocene at 30–50°C promoted by the participation of strong and weak carboxylic acids HX is studied. The radical chain mechanism of the process is established, its kinetics characteristics are determined as well as the composition of the products among which other derivatives of ferrocene have been found. Based on the results of the present study and the earlier obtained data on oxidation of hydroxymethylferrocene a mechanism of initiation of the chains general for both metallocomplexes is suggested. It includes the formation of the intermediate CH₂OR (R = H, C₂H₅) and its subsequent oxidative transformations leading to the formation of the peroxide radical C₅H₄Fe^+·C₅H₄-CH₂O₂ ^· and ROH. The role of the approaching and orientation effect in transformations of this intermediate is discussed as well as the mechanism of the investigated reaction in general.     

Kinetic regularities of conversion of ozone complexes with arenes

The kinetic regularities of conversion of ozone complexes with several substituted benzenes (ArX = C₆H₅Me, C₆H₅Et, C₆H₅CHMe₂, C₆H₅CMe₃, C₆H₅F, C₆H₅Cl,m-BrC ₆ H ₅ Me, and C₆H₅CH₂Cl) were studied by spectrophotometry. The rate of consumption of [ArX · O₃ in a CH₂Cl₂-ArX solution obeys the kinetic equationW =k ₀[ArX · O₃]+k ₁ [ArX · O3][ArX]. The values of the rate constants ko andk ₁for the complexes studied were determined at -60+0 °C.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 371–374, 'February, 1996.     

Catalytic oxidation of fluorobenzene by molecular oxygen

Kinetic and thermal-desorption methods have been applied to the oxidation of fluorobenzene by molecular oxygen. The catalytic oxidation mechanism for fluorobenzene is similar to that for benzene. A suggestion is made on why there is no fluoromaleic anhydride in the oxidation products from fluorobenzene.Translated from, Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 25, No. 1, pp. 116–119, January–February, 1989.