ClO 2 Research Articles

Chemically Bonded α-Fe2 O3 /Bi4 MO8 Cl Dot-on-Plate Z-Scheme Junction with Strong Internal Electric Field for Selective Photo-oxidation of Aromatic Alcohols.

Inferior contact interface and low charge transfer efficiency seriously restrict the performance of heterojunctions. Herein, chemically bonded α-Fe2 O3 /Bi4 MO8 Cl (M=Nb, Ta) dot-on-plate Z-scheme junctions with strong internal electric field are crafted by an in situ growth route. Experimental and theoretical results demonstrate that the internal electric field provides a powerful driving force for vectorial migration of photocharges between Bi4 MO8 Cl and α-Fe2 O3 , and the interfacial Fe-O bond not only serves as an atomic-level charge flow highway but also lowers the charge transfer energy barrier, thereby accelerating Z-scheme charge transfer and realizing effective spatial charge separation. Impressively, α-Fe2 O3 /Bi4 MO8 Cl manifests a significantly improved photocatalytic activity for selective oxidation of aromatic alcohols into aldehydes (Con. ≥92 %, Sel. ≥96 %), with a performance improvement of one to two orders of magnitude. This work presents atomic-level insight into interfacial charge flow steering.

Atmospheric chemistry of (Z)- and (E)-1,2-dichloroethene: kinetics and mechanisms of the reactions with Cl atoms, OH radicals, and O3.

Smog chambers interfaced with in situ FT-IR detection were used to investigate the kinetics and mechanisms of the Cl atom, OH radical, and O3 initiated oxidation of (Z)- and (E)-1,2-dichloroethene (CHClCHCl) under atmospheric conditions. Relative and absolute rate methods were used to measure k(Cl + (Z)-CHClCHCl) = (8.80 ± 1.75) × 10-11, k(Cl + (E)-CHClCHCl) = (8.51 ± 1.69) × 10-11, k(OH + (Z)-CHClCHCl) = (2.02 ± 0.43) × 10-12, k(OH + (E)-CHClCHCl) = (1.94 ± 0.43) × 10-12, k(O3 + (Z)-CHClCHCl) = (4.50 ± 0.45) × 10-21, and k(O3 + (E)-CHClCHCl) = (1.02 ± 0.10) × 10-19 cm3 molecule-1 s-1 in 700 Torr of N2/air diluent at 298 ± 2 K. Pressure dependencies for the Cl atom reaction kinetics were observed for both isomers, consistent with isomerization occurring via Cl atom elimination from the chemically activated CHCl-CHCl-Cl adduct. The observed products from Cl initiated oxidation were HC(O)Cl (117-133%), CHCl2CHO (29-30%), and the corresponding CHClCHCl isomer (11-20%). OH radical initiated oxidation gives HC(O)Cl as a major product. For reaction of OH with (E)-CHClCHCl, (Z)-CHClCHCl was also observed as a product. A significant chlorine atom elimination channel was observed experimentally (HCl yield) and supported by computational results. Photochemical ozone creation potentials of 12 and 11 were estimated for (Z)- and (E)-CHClCHCl, respectively. Finally, an empirical kinetic relationship is explored for the addition of OH radicals or Cl atoms to small alkenes. The results are discussed in the context of the atmospheric chemistry of (Z)- and (E)-CHClCHCl.

Estimation of Rate Constants for Reactions of Organic Compounds under Atmospheric Conditions

Structure–activity (SAR) methods are presented for estimating rate constants at 298 K and approximate temperature dependences for the reactions of organic compounds with OH, NO3, and Cl radicals and O3, and O(3P) in the lower atmosphere. These are needed for detailed mechanisms for the atmospheric reactions of organic compounds. Base rate constants are assigned for the various types of H-abstraction and addition reactions, with correction factors for substituents around the reaction site and in some cases for rings and molecule structure or size. Rate constant estimates are made for hydrocarbons and a wide variety of oxygenates, organic nitrates, amines, and monosubstituted halogen compounds. Rate constants for most hydrocarbons and monofunctional compounds can be estimated to within ±30%, though predictions are not as good for multifunctional compounds, and predictions for ~15% of the rate constants are off by more than a factor of 2. Estimates are more uncertain in the case of NO3 and O3 reactions. The results serve to demonstrate the capabilities and limitations of empirical methods for predicting rate constants for the full variety of organic compounds that may be of interest. Areas where future work is needed are discussed.

Quality Changes of Strawberry by Slow-released ClO 2 Gas Gel-pack during Storage

Quality Changes of Strawberry by Slow-released ClO 2 Gas Gel-pack during Storage

Atmospheric Chemistry of Tetrahydrofuran, 2-Methyltetrahydrofuran, and 2,5-Dimethyltetrahydrofuran: Kinetics of Reactions with Chlorine Atoms, OD Radicals, and Ozone.

FTIR smog chamber techniques were used to study the kinetics of the gas-phase reactions of Cl atoms, OD radicals, and O3 with the five-membered ring-structured compounds tetrahydrofuran (C4H8O, THF), 2-methyltetrahydrofuran (CH3C4H7O, 2-MTHF), 2,5-dimethyltetrahydrofuran ((CH3)2C4H5O, 2,5-DMTHF), and furan (C4H4O). The rate coefficients determined using relative rate methods were kTHF+Cl = (1.96 ± 0.24) × 10(-10), kTHF+OD = (1.81 ± 0.27) × 10(-11), kTHF+O3 = (6.41 ± 2.90) × 10(-21), k2-MTHF+Cl = (2.65 ± 0.43) × 10(-10), k2-MTHF+OD = (2.41 ± 0.51) × 10(-11), k2-MTHF+O3 = (1.87 ± 0.82) × 10(-20), k2,5-DMTHF+OD = (4.56 ± 0.68) × 10(-11), k2,5-DMTHF+Cl = (2.84 ± 0.34) × 10(-10), k2,5-DMTHF+O3 = (4.58 ± 2.18), kfuran+Cl = (2.39 ± 0.27) × 10(-10), and kfuran+O3 = (2.60 ± 0.31) × 10(-18) molecules cm(-3) s(-1). Rate coefficients of the reactions with ozone were also determined using the absolute rate method under pseudo-first-order conditions. OD radicals, in place of OH radicals, were produced from CD3ONO to avoid spectral overlap of isopropyl and methyl nitrite with the reactants. The kinetics of OD radical reactions are expected to resemble the kinetics of OH radical reactions, and the rate coefficients of the reactions with OD radicals were used to calculate the atmospheric lifetimes with respect to reactions with OH radicals. The lifetimes of THF, 2-MTHF, and 2,5-DMTHF are approximately 15, 12, and 6 h, respectively.

Acute liver failure impairs function and expression of breast cancer‐resistant protein (BCRP) at rat blood–brain barrier partly via ammonia‐ROS‐ERK1/2 activation

We once reported that P-glycoprotein (P-GP) and multidrug resistance-associated protein 2 (MRP2) were oppositely regulated at the blood-brain barrier (BBB) of thioacetamide-induced acute liver failure (ALF) rats. This study aimed to investigate whether ALF affected function and expression of breast cancer-resistant protein (BCRP) at the BBB of rats and the role of ammonia in the regulation. ALF rats were developed by intraperitoneal (i.p.) injection of thioacetamide (300mg/kg) for 2days. Hyperammonemic rats were developed by NH4 Ac (i.p. 4.5mmol/kg). BCRP function and expression were measured by brain distribution of specific substrates (prazosin and methotrexate) and western blot, respectively. MDCK-BCRP cells and primarily cultured rat brain microvessel endothelial cells (rBMECs) were employed to investigate possible mechanisms through which ammonia regulated BCRP function and expression. The results showed that both ALF and hyperammonemia significantly weakened function and expression of BCRP in the brain of rats. The function and expression of BCRP in MDCK-BCRP cells and rBMECs were strikingly decreased after exposure to NH4 Cl and H2 O2 , accompanied by remarkable increases in the levels of phosphorylated ERK1/2 and reactive oxygen species (ROS). The altered BCRP expression and function by ammonia and H2 O2 were restored by ROS scavenger N-acetylcysteine and ERK1/2 inhibitor U0126. Markedly increased levels of ERK1/2 phosphorylation and ROS were found in the brains of ALF rats and hyperammonemic rats. All above results indicated ALF down-regulated expression and function of BCRP at BBB of rats partly via hyperammonemia. Activation of ROS-mediatedERK1/2 phosphorylation may be one of the reasons that ammonia impaired BCRP expression and function at the BBB. The present study showed that the expression and function of breast cancer resistant protein (BCRP) at blood-brain barrier (BBB) of thioacetamide-induced ALF rats were down-regulated which partly attribute to hyperammonemia. Activation of ROS-mediated ERK1/2 phosphorylation may be one of the reasons that ammonia suppressed BCRP expression and function. Impaired BCRP at BBB might enhanced pharmacological/toxic effects of corresponding substrates on CNS.

Atmospheric chemistry of cis-CF3CH[dbnd]CHCl (HCFO-1233zd(Z)): Kinetics of the gas-phase reactions with Cl atoms, OH radicals, and O3

FTIR smog chamber techniques were used to measure the rate coefficients k(Cl+cis-CF3CHCHCl)=(6.26±0.84)×10–11, k(OH+cis-CF3CHCHCl)=(8.45±1.52)×10–13, and k(O3+cis-CF3CHCHCl)=(1.53±0.12)×10–21cm3molecule–1s–1. The atmospheric lifetime of cis-CF3CHCHCl is determined by reaction with OH radicals and is estimated to be 14 days. The infrared spectrum of cis-CF3CHCHCl was recorded and the integrated absorption over the range 600–2000cm−1 was measured to be (1.48±0.07)×10–16cmmolecule−1. Accounting for non-uniform horizontal and vertical mixing leads to a GWP100 value of essentially zero. Correction to account for unwanted Cl atom chemistry in our previous relative rate study of the kinetics of the reaction of OH with trans-CF3CHCHCl gives k(OH+trans-CF3CHCHCl)=(3.61±0.37)×10–13cm3molecule–1s–1.

Kinetics of the gas-phase reactions of some unsaturated alcohols with Cl atoms and O3

Abstract Reactions of Cl atoms with 3-buten-1-ol, 3-methyl-3-buten-1-ol, 2-methyl-3-buten-1-ol and 4-penten-2-ol were investigated using relative technique with gas chromatograph coupled with flame ionization detection (GC-FID). At 298 ± 1 K and 1.01 × 10 5 Pa, the rate coefficients measured (in units of 10 −10 cm 3 molecule −1 s −1 ) were 3.63 ± 0.49, 4.13 ± 0.56, 3.51 ± 0.48, and 3.62 ± 0.49, respectively. The quoted errors included 2σ from the least-squares analysis and also 10% errors caused by the uncertainty of the reference rate coefficients. In addition, rate coefficients for reactions of the unsaturated alcohols with O 3 were determined using absolute method. The values obtained have been presented, compared with those of their alkene structural homologues and discussed. Reactivity trends and atmospheric implications have also been discussed.

Atmospheric Chemistry of Sulfuryl Fluoride: Reaction with OH Radicals, Cl Atoms and O3, Atmospheric Lifetime, IR Spectrum, and Global Warming Potential

Sulfuryl fluoride (SO2F2) is a radiatively active industrial chemical released into the atmosphere in significant (ktonne/ year) quantities. The potential for SO2F2 to contribute to radiative forcing of climate change needs to be assessed. Long path length FTIR/smog chamber techniques were used to investigate the kinetics of the gas-phase reactions of Cl atoms, OH radicals, and O3 with SO2F2, in 700 Torr total pressure of air or N2 at 296 +/- 1 K. Upper limits of k(Cl + SO2F2) < 9 x 10(-19), k(OH + SO2F2) < 1.7 x 10(-14) and k(O3 + SO2F2) < 5.5 x 10(-24) cm3 molecule(-1) s(-1) were determined. Reaction with Cl atoms, OH radicals, or O3 does not provide an efficient removal mechanism for SO2F2. The infrared spectrum of SO2F2 is reported and a radiative efficiency of 0.196 W m(-2) ppbv(-1) was calculated. Historic production data estimates are presented which provide an upper limit for expected atmospheric concentrations. The radiative forcing of climate change associated with emissions of SO2F2 depends critically on the atmospheric lifetime of SO2F2. Further research is urgently needed to define the magnitude of potential nonatmospheric sinks.

Atmospheric chemistry of trans-CF3CHCHF: Kinetics of the gas-phase reactions with Cl atoms, OH radicals, and O3

Abstract Long path length FTIR-smog chamber techniques were used to measure k(Cl + t-CF3CH CHF) = (4.64 ± 0.59) × 10−11, k(OH + t-CF3CH CHF) = (9.25 ± 1.72) × 10−13, and k(O3 + t-CF3CH CHF) = (2.81 ± 0.21) × 10−21 cm3 molecule−1 s−1 in 700 Torr of air diluent at 296 K. The atmospheric lifetime of t-CF3CH CHF is determined by its reaction with OH and is approximately two weeks. t-CF3CH CHF has an integrated IR absorption cross section(650–2000 cm−1) of (1.94 ± 0.10) × 10−16 cm molecule−1 and a global warming potential of approximately 6 (100-year time horizon). As part of this work the reaction of ozone with C2H4 was determined to proceed with a rate constant of (1.46 ± 0.13) × 10−18 cm3 molecule−1 s−1 in 700 Torr of air at 296 K.

A Series of [3 + 2] Cycloaddition Products from the Reaction of Rhenium Oxo Complexes with Diphenyl Ketene

The reaction of rhenium (VII) trioxo complexes containing the ligand sets scorpionate, [HB(pz)3]ReO3 (6), [Ph-B(pz)3]ReO3 (7), and [[HC(pz)3]ReO3][ReO4] (8) and pyridine/pyridine-type ligands [(4,7-diphenyl-1,10-phen)(Br)ReO3] (12), [(4,4'-di-tert-butyl-2,2'-dipyridyl)(Cl)ReO3] (13), and [(py)2Re(Cl)O3] (4), with diphenyl ketene, has led to the isolation of six novel [3 + 2] cycloaddition products. These air-stable solids 9-11 and 15-17 are the result of [3 + 2] addition of the O=Re=O motif across the ketene C=C double bond. Five of the six [3 + 2] cycloaddition products have been structurally characterized by single-crystal X-ray diffraction and in all cases by 13C NMR and IR spectroscopies.

A Novel Layered Niobium Oxychloride Compound Based on Nb2 Pairs and Nb6 Octahedral Clusters: Synthesis and Crystal and Electronic Structures of Nb10Cl16O7.

AbstractFor Abstract see ChemInform Abstract in Full Text.

A novel layered niobium oxychloride compound based on Nb2 pairs and Nb6 octahedral clusters: synthesis and crystal and electronic structures of Nb10Cl16O7.

The synthesis, single crystal structure determination, and electronic structure of Nb10Cl16O7, the first Nb6 oxychloride stabilized without countercation, are reported in this work. The crystal structure is very original since it consists of layers built up from both Nb6 octahedral clusters and Nb2 pairs. The Nb6Oi6Cli6Cla6 and Nb2(mu2-Cl)2Cl4O4 units form [Nb6Cli6Oi4O(i-i)(2/2)Cl(a-a)(4/2)Cla2]infinity infinite chains and [(Nb2(mu2-Cl)2O(2/2)Cl(4/2)O2)2]infinity double chains, respectively, that are interconnected by shared oxygen and chlorine ligands leading to layers. The cohesion of the three-dimensional structure (3D) is ensured by van der Waals contacts between layers that are randomly stacked along the [011] direction. Structural correlations between Nb10Cl16O7 and related Nb6 cluster oxyhalides, as well as NbOCl2 and NbCl4 containing Nb2 pairs, are discussed. DFT results show that among the 20 valence electrons involved in the metal-metal bonding states, 14 electrons belong to the octahedral Nb6Cli6Oi6Cla6 unit whereas the 6 others (i.e., 1.5 per Nb atom) participate in the bonding in the distorted [(Nb2(mu2-Cl)2O(2/2)Cl(4/2)O2)2]infinity double chains.

An ab initio direct-trajectory study of the photodissociation of ClOOCl

The photodissociation of chlorine peroxide, ClOOCl, is studied with classical trajectories where the energy and gradient are computed on the fly by means of the state-averaged (sa) complete active space self-consistent field (CASSCF) with the DZP(+) basis set. We show that six electronically excited states are involved in the process of decomposition, which proceeds via several competing pathways and at least three electronically unique fragment channels. The problem is treated in four-dimensional (4D) (C2 constraint) and five-dimensional (5D) (planar constraint) frameworks in order to model the mechanisms of synchronous and asynchronous or stepwise dissociation, respectively. A single trajectory with the initial conditions of a nonvibrating, nonrotating molecule is propagated on each excited state surface for an average time of 10 fs for the purposes of determining the early stages of bond breaking. We show that even in such a short propagation time the pathway competition can be more or less unambiguously understood. The results indicate that in the regime of a 308 nm photolysis, the major dissociation fragments are Cl atoms and O2 molecules, both in the ground state. The higher energy regime of a 248 nm photoexcitation yields additional fragments, e.g., ClO(X 2Π), O(3P) and ClOO(X 2A″,1 2A′). We have achieved an overall qualitative agreement with experiment that more than 70% of the available energy is transferred into the translational energy of the products for the case of the synchronous concerted dissociation. In all the cases, the rotational excitation of produced molecular oxygen is very high, while its vibration is in v=0. Implications of the results on the stratospheric ozone depletion cycle are also presented.

The ClO4 radical: Experiment versus theory

The chlorine tetroxide radical and its anion have been investigated with unrestricted Hartree–Fock, density functional and hybrid Hartree–Fock/density functional methods, perturbation theory, and coupled cluster methods. It is predicted that the minimum on the ClO4 radical potential energy surface corresponds to the 2B2 ground electronic state, a C2v-symmetry structure. The C3v structure identified experimentally lies a few kcal mol−1 higher energetically. A Cs symmetry structure lies very close energetically to the C2v minimum at some levels of theory. Adiabatic electron affinities, equilibrium geometries, harmonic vibrational frequencies, infrared intensities, isotopic shifts, and dipole moments are presented for all methods. Comparisons with recent experimental vibrational data for the radical are made. It is predicted that the C2v equilibrium geometry of the ground state is Re(Cl–O1)=1.502 Å, Re(Cl–O2)=1.424 Å, θe1=93.6° and θe2=114.2°. The adiabatic electron affinity of the ClO4 radical is predicted to lie near 5.2 eV.

特集 「地球環境および地域環境と化学」 水素を含むハロカーボン類の塩素原子と酸素による分解

Some products of the degradation of hydrochlorofluorocarbons (HCFCs) by reaction with Cl atoms and O2 were studied by FT-IR. The degradation of CH3CCl2F(HCFC 141 b) was initiated by H abstraction, and then CH2CCl2F was oxidized, leading to formation of either HCHO and COClF or CCl2FCHO, and finally COClF, CO and CO2 were formed. In the addition reaction of Cl to CH2CCIF and subsequent reactions, both CH2ClCOF and COClF were observed. It was presumed that CHCl2CF3(HCFC 123) reacted with Cl and the produced radical was oxidized to CF3COCl. On the other hand, in the reaction of CHCl2CCl3 with Cl and O2, CCl3COCl, COCl2, CO and CO2 were produced and it indicates that C-C bond cleavage took place. CF3CF2CHCl2 (HCFC 225 ca) and CClF2CF2CHCIF(HCFC 225 cb) were degraded to CF3CF2COCl and CClF2CF2COF, respectively.

Molecular conformation of GABA.

CURTIS et al.1,2 have described evidence suggesting that the alkaloid bicuculline is a specific antagonist to the action of γ-aminobutyric acid (GABA), a possible inhibitory transmitter in the mammalian brain3,4. By considering structural models, they suggested3 as a stereochemical basis for this antagonism a geometrical configuration in which the N and Ol=C1—O2 of GABA is isosteric with the N and C2—Cl—Ol in bicuculline (Fig. 1a and b). An alternative configuration of GABA, which would give a greater degree of stereochemical similarity to bicuculline, is depicted in Fig. 1c. In both molecules the N is now seen to be isosterically related to Ol=Cl—O2 and located at an angle of about 40° to the plane of the O=Cl—O group viewed towards C2 (Fig. 2). In contrast to Curtis's suggestion, there is now not only geometrical congruence but also identical matching of atomic species.