Oxygenation and chlorination of aromatic hydrocarbons with hydrochloric acid photosensitized by 9-mesityl-10-methylacridinium under visible light irradiation

Efficient photocatalytic oxygenation of toluene occurs under visible light irradiation of 9-mesityl-10-methylacridinium (Acr⁺–Mes) in oxygen-saturated acetonitrile containing toluene and aqueous hydrochloric acid with a xenon lamp for 15 h. The oxygenated products, benzoic acid (70 %) and benzaldehyde (30 %), were formed after the photoirradiation. The photocatalytic reaction is initiated by intramolecular photoinduced electron transfer from the mesitylene moiety to the singlet excited state of the Acr⁺ moiety of Acr⁺–Mes, which affords the electron-transfer state, Acr^?–Mes^?+. The Mes^?+ moiety can oxidize chloride ion (Cl^?) by electron transfer to produce chlorine radical (Cl^?), whereas the Acr^? moiety can reduce O₂ to O ₂ ^?? . The Cl^? radical produced abstracts a hydrogen from toluene to afford benzyl radical in competition with the bimolecular radical coupling of Cl^?. The benzyl radical reacts with O₂ rapidly to afford the peroxyl radical, leading to the oxygenated product, benzaldehyde. Benzaldehyde is readily further photooxygenated to yield benzoic acid with Acr^?–Mes^?+. In the case of an aromatic compound with electron-donating substituents, 1,3,5-trimethoxybenzene, photocatalytic chlorination occurred efficiently under the same photoirradiation conditions to yield a monochloro-substituted compound, 2,4,6-trimethoxychlorobenzene.     

Effect of sodium cation on the electrochemical reduction of CO<Subscript>2</Subscript> at a copper electrode in methanol

The electrochemical reduction of CO₂ with a Cu electrode in methanol was investigated with sodium hydroxide supporting salt. A divided H-type cell was employed; the supporting electrolytes were 80 mmol dm⁻³ sodium hydroxide in methanol (catholyte) and 300 mmol dm⁻³ potassium hydroxide in methanol (anolyte). The main products from CO₂ were methane, ethylene, carbon monoxide, and formic acid. The maximum current efficiency for hydrocarbons (methane and ethylene) was 80.6%, at −4.0 V vs Ag/AgCl, saturated KCl. The ratio of current efficiency for methane/ethylene, r _f(CH₄)/r _f(C₂H₄), was similar to those obtained in LiOH/methanol-based electrolyte and larger relative to those in methanol using KOH, RbOH, and CsOH supporting salts. In NaOH/methanol-based electrolyte, the efficiency of hydrogen formation, a competing reaction of CO₂ reduction, was suppressed to below 4%. The electrochemical CO₂ reduction to methane may be able to proceed efficiently in a hydrophilic environment near the electrode surface provided by sodium cation.     

Single Chromium Atoms Supported on Titanium Dioxide Nanoparticles for Synergic Catalytic Methane Conversion under Mild Conditions

Direct conversion of methane to value‐added chemicals with high selectivity under mild conditions remains a great challenge in catalysis. Now, single chromium atoms supported on titanium dioxide nanoparticles are reported as an efficient heterogeneous catalyst for direct methane oxidation to C1 oxygenated products with H₂O₂ as oxidant under mild conditions. The highest yield for C1 oxygenated products can be reached as 57.9 mol mol_Cr^?1 with selectivity of around 93 % at 50 °C for 20 h, which is significantly higher than those of most reported catalysts. The superior catalytic performance can be attributed to the synergistic effect between single Cr atoms and TiO₂ support. Combining catalytic kinetics, electron paramagnetic resonance, and control experiment results, the methane conversion mechanism was proposed as a methyl radical pathway to form CH₃OH and CH₃OOH first, and then the generated CH₃OH is further oxidized to HOCH₂OOH and HCOOH.     

Tunable Diode Laser Diagnostic Studies of H2-Ar-O2 Microwave Plasmas Containing Methane or Methanol

Tunable infrared diode laser absorption spectroscopy has been used to detect the methyl radical and ten stable molecules in H₂-Ar-O₂ microwave plasmas containing up to 7.2% of methane or methanol, under both flowing and static conditions. The degree of dissociation of the hydrocarbons varied between 30 and 90% and the methyl radical concentration was found to be in the range 10 ¹⁰ –10 ¹² molecules cm ^–3 . The methyl radical concentration and the concentrations of the stable C-2 hydrocarbons C ₂ H ₂ , C ₂ H ₄ , and C ₂ H ₆ , produced in the plasma decayed exponentially when increasing amounts of O ₂ were added at fixed methane or methanol partial pressures. In addition to detecting the hydrocarbon species, the major products CO, CO ₂ , and H ₂ O were also monitored. For the first time, formaldehyde, formic acid, and methane were detected in methanol microwave plasmas, formaldehyde was detected in methane microwave plasmas. Chemical modeling with 57 reactions was used to successfully predict the concentrations in methane plasmas in the absence of oxygen and the trends for the major chemical product species as oxygen was added.     

Electrochemical reduction of carbon dioxide on copper in methanol with various potassium supporting electrolytes at low temperature

The electrochemical reduction of CO₂ at a Cu electrode was investigated in a methanol-based electrolyte using such potassium supporting salts as CH₃COOK, KBr, KI and KSCN at extremely low temperature (−30 °C). The main products obtained from CO₂ by the electrochemical reduction were methane, ethylene, ethane, carbon monoxide and formic acid. The maximum Faradaic efficiency of ethylene was 19.9% in KI/methanol-based catholyte at −3.0 V vs. Ag/AgCl saturated KCl. The best methane formation (27.0%) was obtained in CH₃COOK/methanol electrolyte at −3.0 V. In the system containing a potassium halide, the efficiency of hydrogen formation, being a competitive reaction against CO₂ reduction, was suppressed to less than 8.1%. The product selectivity of the electrochemical reduction of CO₂ in methanol was greatly affected by the anionic species. This research can contribute to the large-scale manufacturing of useful organic products from readily available and cheap raw materials: CO₂-saturated methanol from industrial absorbers (the Rectisol process). Received: 11 November 1998 / Accepted: 1 February 1999     

Darstellung und Eigenschaften der Imidodiphosphorsäureamide

Preparation and Properties of Imidodiphosphoric Acid Amides Trichlorophosphazene phosphoryldichloride, Cl₃P?N? P(O)Cl₂, reacts with the stoichiometric amount of anhydrous formic acid resulting the tetrachloride of the imidodiphosphoric acid, Cl₂(O)P? NH? P(O)Cl₂. This tetrachloride yields with diazomethane the N-methyl compound, Cl₂(O)P? N(CH₃)? P(O)Cl₂. The tetramide of the imidodiphosphoric acid and its octalkyl derivatives are obtained by reaction of the tetrachloride with ammonia, dimethylamine, and diethylamine, respectively.     

Direct Conversion of Methane with Carbon Dioxide Mediated by RhVO3− Cluster Anions

Direct conversion of methane with carbon dioxide to value‐added chemicals is attractive but extremely challenging because of the thermodynamic stability and kinetic inertness of both molecules. Herein, the first dinuclear cluster species, RhVO₃^?, has been designed to mediate the co‐conversion of CH₄ and CO₂ to oxygenated products, CH₃OH and CH₂O, in the temperature range of 393–600 K. The resulting cluster ions RhVO₃CO^? after CH₃OH formation can further desorb the [CO] unit to regenerate the RhVO₃^? cluster, leading to the successful establishment of a catalytic cycle for methanol production from CH₄ and CO₂ (CH₄+CO₂→CH₃OH+CO). The exceptional activity of Rh‐V dinuclear oxide cluster (RhVO₃^?) identified herein provides a new mechanism for co‐conversion of two very stable molecules CH₄ and CO₂.     

Spontaneous Reduction of Mononuclear High‐Spin Iron(III) Complexes to Mononuclear Low‐Spin Iron(II) Complexes in Aqueous Media and Nuclease Activity via Self‐Activation

Mononuclear high‐spin [Fe^III(Pyimpy)Cl₃]?2 CH₂Cl₂ ( 1 ?2 CH₂Cl₂) and [Fe^III(Me‐Pyimpy)Cl₃] ( 2 ), as well as low‐spin Fe^II(Pyimpy)₂](ClO₄)₂ ( 3 ) and [Fe^II(Me‐Pyimpy)₂](ClO₄)₂ ( 4 ) complexes of tridentate ligands Pyimpy and Me‐Pyimpy have been synthesized and characterized by analytical techniques, spectral, and X‐ray structural analyses. We observed an important type of conversion and associated spontaneous reduction of mono‐chelated high‐spin Fe^III ( 1 ?2 CH₂Cl₂ and 2 ) complexes to low‐spin bis‐chelated Fe^II complexes 3 and 4 , respectively. This process has been explored in detail by UV/Vis, fluorescence, and ¹H NMR spectroscopic measurements. The high positive potentials observed in electrochemical studies suggested a better stabilization of Fe^II centers in 3 and 4 . Theoretical studies by density functional theory (DFT) calculations supported an increased stabilization for 3 in polar solvents. Self‐activated nuclease activity of complexes 1 ?2CH₂Cl₂ and 2 during their spontaneous reduction was examined for the first time and the mechanism of nuclease activity was investigated.     

Coordination chemistry of bis(2-pyridylimine) ligands with Ag(I): formation of two structurally different coordination polymers and one metallocycle controlled by linker and the solvent system

Reaction of equimolar amounts of AgClO₄ and bis[4-(2-pyridylmethyleneamino)phenyl] methane (L¹) or bis[4-(2-pyridylmethyleneamino)phenyl] ether (L²) in a 1:1 solvent mixture of CH₃CN and CH₂Cl₂ leads to the formation of two infinite coordination polymers of the composition {[Ag(L¹)]ClO₄·CH₃CN}_n (1) and {[Ag(L²)]ClO₄·CH₂Cl₂}_n (2). Whereas 1 represents a homochiral single-stranded helicate the related complex 2 shows a typical zigzag chain arrangement. Both structures are characterized by a distorted tetrahedral coordination environment of the Ag(I) centres each based on a N₄ coordination pattern of two ligand molecules. The resulting strands are connected by a hydrogen bonding network including ClO₄ ^? anions and solvent molecules forming 2-D layers. Additional ?ШC?? and CH?C?? interactions between the aromatic parts of the ligand molecules give a 3-D arrangement of the packing. In contrast, a discrete dinuclear metallocycle, [Ag₂(L²)₂](ClO₄)₂·CH₃OH (3), has been formed by reaction of AgClO₄ with L² when CH₂Cl₂ in the solvent mixture was replaced by CH₃OH. Again each Ag(I) has a distorted tetrahedral geometry and is coordinated to two pyridylimine units of two ligand molecules. Additional weak hydrogen bonds involving perchlorate and solvent molecules as well as edge-to-face and face-to-face ?ШC?? interactions allow a 3-D packing arrangement.     

Theoretical study on the gas‐phase reaction mechanism between rhodium monoxide and methane for methanol production

The gas‐phase reaction mechanism between methane and rhodium monoxide for the formation of methanol, syngas, formaldehyde, water, and methyl radical have been studied in detail on the doublet and quartet state potential energy surfaces at the CCSD(T)/6‐311+G(2d, 2p), SDD//B3LYP/6‐311+G(2d, 2p), SDD level. Over the 300–1100 K temperature range, the branching ratio for the Rh(⁴F) + CH₃OH channel is 97.5–100%, whereas the branching ratio for the D‐CH₂ORh + H₂ channel is 0.0–2.5%, and the branching ratio for the D‐CH₂ORh + H₂ channel is so small to be ruled out. The minimum energy reaction pathway for the main product methanol formation involving two spin inversions prefers to both start and terminate on the ground quartet state, where the ground doublet intermediate CH₃RhOH is energetically preferred, and its formation rate constant over the 300–1100 K temperature range is fitted by k_CH3RhOH = 7.03 × 10⁶ exp(?69.484/RT) dm³ mol^?1 s^?1. On the other hand, the main products shall be Rh + CH₃OH in the reactions of RhO + CH₄, CH₂ORh + H₂, Rh + CO +2H₂, and RhCH₂ + H₂O, whereas the main products shall be CH₂ORh + H₂ in the reaction of Rh + CH₃OH. Meanwhile, the doublet intermediates H₂RhOCH₂ and CH₃RhOH are predicted to be energetically favored in the reactions of Rh + CH₃OH and CH₂ORh + H₂ and in the reaction of RhCH₂ + H₂O, respectively. © 2009 Wiley Periodicals, Inc. J Comput Chem 2010     

The atmospheric oxidation of hydroxyacetone: Chemistry of activated and stabilized CH3C(O)CH(OH)OO• radicals between 252 and 298 K

The products of the Cl-atom-initiated oxidation of hydroxyacetone (HYAC, CH₃C(O)CH₂OH) have been examined under conditions relevant to the earth's lower atmosphere. Over the range of temperatures studied (252-298 K), in the absence of NO_x, methylglyoxal (CH₃C(=O)CH=O, MGLY) was formed with a primary yield >84% (96 ± 9% at 298 K), while in the presence of elevated NO_x, MGLY and formic acid were both formed as major primary products. In contrast to a previous study, acetic acid was not identified as a major primary product under the conditions studied. The results are quantitatively interpreted from a consideration of the formation of a stabilized CH₃C(O)CH(OH)OO• radical, either in a ≈50% yield from the addition of O₂ to CH₃C(O)CH•(OH) or in 100% yield from the addition of HO₂ to MGLY. At high temperature and low NO_x, decomposition of the stabilized CH₃C(O)CH(OH)OO• radical to MGLY is favored, while lower temperatures and conditions of high NO_x favor bimolecular reactions of the stabilized radical, with subsequent production of formic acid. Analysis of the data allows for a semiquantitative determination of K₃ = (2.9 ± 0.4) × 10⁻¹⁶ cm³ molecule⁻¹, for the HO₂ + MGLY ↔ CH₃C(O)CH(OH)OO• equilibrium process at 298 K and a roughly order of magnitude increase in K₃ at 252 K.     

Palladium carbene complexes as persistent radicals

A series of palladium(ii) radical carbene complexes, [PC˙(sp²)P]PdI, [PC˙(sp²)P]PdBr, and [PC˙(sp²)P]PdCl (PC(sp³)H₂P = bis[2-(di-iso-propylphosphino)-phenyl]methane), is described. Compound [PC˙(sp²)P]PdI dimerizes to {[PC(sp²)P]PdI}₂ in the solid state, akin to the formation of Gomberg''s dimer. While the bromo and the iodo derivatives could be obtained from the oxidation of [PC(sp²)P]Pd(PMe₃) by the respective dihalogens, a halogen transfer reaction from CH₂Cl₂ was used for the formation of [PC˙(sp²)P]PdCl. The halogen transfer from CH₂X₂ (X = Cl, Br, I) could be used to obtain all three radical carbene palladium complexes and also allowed the isolation of [PC(CH₂)P]Pd(PMe₃), which is the result of methylene group transfer from CH₂X₂. Compound [PC(CH₂)P]Pd(PMe₃) was independently synthesized from [PC(CH₃)HP]PdCl₂, which contains a supporting ligand analogous to that of the radical carbene complexes but has one of the hydrogen atoms replaced by a methyl group. All three carbene radical species abstract a hydrogen from 9,10-dihydroanthracene or ⁿBu₃SnH.     

Synthesis and Structural Characterization of Six Pentanuclear and Tetranuclear Mo/W‐Cu‐S Clusters with Bis(diphenylphosphanyl) Methane

Six heterothiometalic clusters, namely, [WS₄Cu₄(dppm)₄](ClO₄)₂ · 2DMF · MeCN ( 1 ), [MoS₄Cu₄(dppm)₄](NO₃)₂ · MeCN ( 2 ) [MoS₄Cu₃(dppm)₃](ClO₄) · 4H₂O ( 3 ), [WS₄Cu₃(dppm)₃](NO₃) · 4H₂O ( 4 ), [WS₄Cu₃(dppm)₃]SCN · CH₂Cl₂ ( 5 ), and [WS₄Cu₃(dppm)₃]I · CH₂Cl₂ ( 6 ) [dppm = bis (diphenylphosphanyl)methane] were synthesized. Compounds 1 – 4 were obtained by the reactions of (NH₄)₂MS₄ (M = Mo, W) with [Cu₂(μ₂‐dppm)₂(MeCN)₂(ClO₄)₂] {or [Cu(dppm)(NO₃)]₂} in the presence of 1,10‐phen in mixed solvent (CH₃CN/CH₂Cl₂/DMF for 1 and 2 , CH₂Cl₂/CH₃OH/DMF for 3 and 4 . Compounds 5 and 6 were obtained by one‐pot reactions of (NH₄)₂WS₄ with dppm and CuSCN (or CuI) in CH₂Cl₂/CH₃OH. These clusters were characterized by single‐crystal X‐ray diffraction as well as IR, ¹H NMR, and ³¹P NMR spectroscopy. Structure analysis showed that compounds 1 and 2 are “saddle‐shaped” pentanuclear cationic clusters, whereas compounds 3 – 6 are “flywheel‐shaped” tetranuclear cationic clusters. In 1 and 2 , the MS₄^2– unit (M = W, Mo) is coordinated by four copper atoms, which are further bridged by four dppm molecules. In compounds 3 – 6 , the MS₄^2– unit is coordinated by three copper atoms and each copper atom is bridged by three dppm ligands.     

Anion‐Dependence of Ytterbium Complexes and Their NIR Luminescence

The reaction of 2‐aldehyde‐8‐hydroxyquinoline, histamine, and YbX₃ · 6H₂O (X = NO₃^–, ClO₄^–) affords two ytterbium complexes [Yb(nma)₂] · ClO₄ · 2CH₂Cl₂ ( 1 ) and [Yb(nma)(NO₃)₂(DMSO)] · CH₃OH ( 2 ) (Hnma = N‐(2‐(8‐hydroxylquinolinyl)methane(2‐(4‐imidazolyl)ethanamine))). The crystal structures were determined by X‐ray diffraction and it has been revealed that the anions have played important role in the assembly. In the case of 1 , the Yb³⁺ ions are completely encapsulated by two nma ligands with uncoordinated perchlorate anion balancing the positive charge. In the case of 2 , the Yb³⁺ ions are ligated by the ligand, oxygen atoms of the nitrate ion, and DMSO. Both complexes exhibit essential NIR luminescence of Yb³⁺ ions.     

Effect of added salts on the rates of dissociation and racemization of tris(1,10-phenanthroline)iron(II) ion in aqueous methanol solutions

The kinetics of dissociation and racemization of [Fe(phen)₃]²⁺ have been studied in aqueous methanol solutions containing perchlorate, chloride, and thiocyanate ions. The racemization rate was decreased by ClO^?₄ and increased by SCN^?, while the dissociation rate was decreased by ClO^?₄ and increased slightly by Cl^? and remarkably by SCN^?. The effect of anions on the reaction rates became remarkable with the increase in methanol content of the solutions. The results were reasonably explained in terms of ion association. The dissociation rate of the complex ion in the ion-pair increased in the order, ClO^?₄ < Cl^? < SCN^?, of associated anions, suggesting the ion-pair interchange mechanism for the dissociation. The ion-association constants were determined to be 11 ± 4, 18 ± 4, and 25 ± 15 (I = 0.1, 25°C) for ClO^?₄, Cl^?, and SCN^?, respectively, in 0.64 mole-fraction (0.8 volume-fraction) aqueous methanol.     

Organic Phosphorus Compounds 61. Esterification and chlorination of nitrilo-tri(methylene-phosphonic acid), N(CH2PO3H2)3, and hydroxyethylidenediphosphonic acid,H2O3PC(OH)(CH3)PO3H2, and the corresponding esters

Nitrilo-tri(methylenephosphonic acid) and hydroxyethylidenediphosphonic acid are esterified in high yield when treated with excess orthoformic acid ester under reflux. Because of the high temperature necessary to effect esterification a partial isomerization of hydroxyethylidenediphosphonate to the phosphate-phosphonate isomer V takes place. Chlorination of N(CH₂PO₃H₂)₃ or a mixture of the ester and the acid with PCl₅ yields tris(chloromethyl)amine, N(CH₂Cl)₃. Interaction of N(CH₂Cl)₃ and (EtO)₃P yields nitrilo-tri(methylenephosphonate), which on hydrolysis with HCl conc. produces N(CH₂PO₃H₂)₃. Chlorination of a mixture of hydroxyethylidene-diphosphonic acid and the corresponding ethyl ester IV which contained the phosphate-phosphonate isomer V gave the products VII to XI. Chlorination of the acid III with PCl₅ gave 4 products, i.e., VIII, IX, XI and Cl₂(O)POP(O)Cl₂. The ¹H- and ³¹P-NMR. spectra of the products are discussed.     

Syntheses and structures of one CuI‐containing coordination polymer and two macrocyclic supramolecular complexes based on flexible 1,3,4‐oxadiazole‐containing ligands

Three coordination complexes with Cu^I centres have been prepared using the symmetrical flexible organic ligands 1,3‐bis{[5‐(quinolin‐2‐yl)‐1,3,4‐oxadiazol‐2‐yl]sulfanyl}propane (L1) and 1,4‐bis{[5‐(quinolin‐2‐yl)‐1,3,4‐oxadiazol‐2‐yl]sulfanyl}butane (L2). Crystallization of L1 with Cu(SO₃CF₃)₂ and of L2 with Cu(BF₄)₂ and Cu(ClO₄)₂ in a CH₂Cl₂/CH₃OH mixed‐solvent system at room temperature afforded the coordination complexes catena‐poly[[copper(I)‐μ‐1,3‐bis{[5‐(quinolin‐2‐yl)‐1,3,4‐oxadiazol‐2‐yl]sulfanyl}propane] methanesulfonate dichloromethane 0.6‐solvate], {[Cu(C₂₅H₁₈N₆O₂S₂)](CF₃SO₃)·0.6CH₂Cl₂}_n, (I), bis(μ‐1,4‐bis{[5‐(quinolin‐2‐yl)‐1,3,4‐oxadiazol‐2‐yl]sulfanyl}butane)dicopper(I) bis(tetrafluoridoborate)–dichloromethane–methanol (1/1.5/1), [Cu₂(C₂₆H₂₀N₆O₂S₂)₂](BF₄)₂·1.5CH₂Cl₂·CH₃OH, (II), and bis(μ‐1,4‐bis{[5‐(quinolin‐2‐yl)‐1,3,4‐oxadiazol‐2‐yl]sulfanyl}butane)dicopper(I) bis(perchlorate)–dichloromethane–methanol (1/2/1), [Cu₂(C₂₆H₂₀N₆O₂S₂)₂](ClO₄)₂·2CH₂Cl₂·CH₃OH, (III). Under the control of the dumbbell‐shaped CF₃SO₃⁻ anion, complex (I) forms a one‐dimensional chain and neighbouring chains form a spiral double chain. Under the control of the regular tetrahedron‐shaped BF₄⁻ and ClO₄⁻ anions, complexes (II) and (III) have been obtained as bimetallic rings, which further interact viaπ–π interactions to form two‐dimensional networks. The anions play a decisive role in determining the arrangement of these discrete molecular complexes in the solid state.     

Anionic Effects on Raman OD Stretching Spectra for Alcoholic LiX Solutions (X = Cl−, Br−, I−, ClO4 −, NO3 −, and CH3COO−)

Raman OD stretching spectra of alcoholic LiX (X = Cl^–, Br^–, I^–, ClO₄ ^–, NO₃ ^–, and CH₃COO^–) solutions (alcohols = methanol and ethanol) were measured in the liquid state at room temperature and in the glassy state at liquid nitrogen temperature. The effects of the anions on the Raman OD stretching spectra in these alcoholic solutions are investigated and the structural changes of the solutions are discussed. It is shown that the structure-breaking effects of anions on the intrinsic alcoholic structure increase in the order: Cl^– < Br^– < I^– < ClO₄ ^–. From spectral changes, it seems that CH₃COOLi exerts little effect on the liquid structure of the alcohol.     

Theoretical study on the gas‐phase reaction mechanism between nickel monoxide and methane for syngas production

The comprehensive mechanism survey on the gas‐phase reaction between nickel monoxide and methane for the formation of syngas, formaldehyde, methanol, water, and methyl radical has been investigated on the triplet and singlet state potential energy surfaces at the B3LYP/6‐311++G(3df, 3pd)//B3LYP/6‐311+G(2d, 2p) levels. The computation reveals that the singlet intermediate HNiOCH₃ is crucial for the syngas formation, whereas two kinds of important reaction intermediates, CH₃NiOH and HNiOCH₃, locate on the deep well, while CH₃NiOH is more energetically favorable than HNiOCH₃ on both the triplet and singlet states. The main products shall be syngas once HNiOCH₃ is created on the singlet state, whereas the main products shall be methyl radical if CH₃NiOH is formed on both singlet and triplet states. For the formation of syngas, the minimal energy reaction pathway (MERP) is more energetically preferable to start on the lowest excited singlet state other than on the ground triplet state. Among the MERP for the formation of syngas, the rate‐determining step (RDS) is the reaction step for the singlet intermediate HNiOCH₃ formation involving an oxidative addition of NiO molecule into the C? H bond of methane, with an energy barrier of 120.3 kJ mol^?1. The syngas formation would be more effective under higher temperature and photolysis reaction condition. © 2009 Wiley Periodicals, Inc. J Comput Chem, 2009     

The hydroxyl radical reaction rate constant and atmospheric transformation products of 2‐propoxyethanol

The relative rate technique has been used to measure the hydroxyl radical (OH) reaction rate constant of 2‐propoxyethanol (2PEOH, CH₃CH₂CH₂OCH₂CH₂(OH)). 2PEOH reacts with OH with a bimolecular rate constant of (21.4 ± 6.0) × 10⁻¹² cm³molecule⁻¹s⁻¹ at 297 ± 3 K and 1 atm total pressure, which is a little larger than previously reported [1]. Assuming an average OH concentration of 1 × 10⁶ molecules cm⁻³, an atmospheric lifetime of 13 h is calculated for 2PEOH. In order to more clearly define this hydroxy ether's atmospheric reaction mechanism, an investigation into the OH + 2PEOH reaction products was also conducted. The OH + 2PEOH reaction products and yields observed were: propyl formate (PF, 47 ± 2%, CH₃CH₂CH₂OC(O)H), 2 propoxyethanal (CH₃CH₂CH₂OCH₂C(O)H 15 ± 1%), and 2‐ethyl‐1,3‐dioxolane (5.4 ± 0.4%). The 2PEOH reaction mechanism is discussed in light of current understanding of oxygenated hydrocarbon atmospheric chemistry. The findings reported here can be related to other structurally similar alcohols and may impact regulatory tools such as ground‐level ozone‐forming potential calculations (incremental reactivity) [2]. © 1999 John Wiley & Sons, Inc. Int J Chem Kinet 31: 315–322, 1999