Reaction Fragment Research Articles

Effects of Benzo[a]pyrene on Human Sperm Functions: An In Vitro Study.

Benzo(a)pyrene (BaP) is considered one of the most dangerous air pollutants for adverse health effects, including reproductive toxicity. It is found both in male and female reproductive fluids likely affecting spermatozoa after the selection process through cervical mucus, a process mimicked in vitro with the swim-up procedure. In vitro effects of BaP (1, 5, 10 µM) were evaluated both in unselected and swim-up selected spermatozoa after 3 and 24 h of incubation. BaP reduced total, progressive and hyperactivated motility and migration in a viscous medium both in swim-up selected and unselected spermatozoa. Viability was not significantly affected in swim-up selected but was reduced in unselected spermatozoa. In swim-up selected spermatozoa, increases in the percentage of spontaneous acrosome reaction and DNA fragmentation were observed after 24 h of incubation, whereas no differences between the control and BaP-treated samples were observed in caspase-3 and -7 activity, indicating no effects on apoptotic pathways. ROS species, evaluated by staining with CellROX® Orange and Dihydroethidium, did not differ in viable spermatozoa after BaP treatment. Conversely, the percentage of unviable ROS-positive spermatozoa increased. Our study suggests that BaP present in male and female genital fluids may heavily affect reproductive functions of human spermatozoa.

Tumour status prediction by means of carbon-ion beam irradiation: comparison of washout rates between in-beam PET and DCE-MRI in rats

Objective. Tumour response to radiation therapy appears as changes in tumour vascular condition. There are several methods for analysing tumour blood circulatory changes one of which is dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI), but there is no method that can observe the tumour vascular condition and physiological changes at the site of radiation therapy. Positron emission tomography (PET) has been applied for treatment verification in charged particle therapy, which is based on the detection of positron emitters produced through nuclear fragmentation reactions in a patient’s body. However, the produced positron emitters are washed out biologically depending on the tumour vascular condition. This means that measuring the biological washout rate may allow evaluation of the tumour radiation response, in a similar manner to DCE-MRI. Therefore, this study compared the washout rates in rats between in-beam PET during 12C ion beam irradiation and DCE-MRI. Approach. Different vascular conditions of the tumour model were prepared for six nude rats. The tumour of each nude rat was irradiated by a 12C ion beam with simultaneous in-beam PET measurement. In 10–12 h, the DCE-MRI experiment was performed for the same six nude rats. The biological washout rate of the produced positron emitters (k 2,1st) and the MRI contrast agent (k 2a) were derived using the single tissue compartment model. Main results. A linear correlation was observed between k 2,1st and k 2a, and they were inversely related to fractional necrotic volume. Significance. This is the first animal study which confirmed the biological washout rate of in-beam PET correlates closely with tumour vascular condition measured with the MRI contrast agent administrated intravenously.

Selective formation of fuel BXT compounds from catalytic hydrodeoxygenation of waste biomass over Ni-decorated beta-zeolite

Upgrading of bio-oil extracted from the various components of biomass into transportation fuels is typically attained via surface-assisted hydrodeoxygenation (HDO) reactions. Date palm (Phoenix dactylifera) pits constitute an important category of waste biomass in many parts of the world. Herein, we report a comprehensive integrated experimental-simulation approach to investigate HDO process of vapor fraction generated from pyrolysis of date pits over the metal-supported catalyst Ni/H-Beta zeolite. The catalyst was synthesized and characterized using various techniques including XRD, FTIR, SEM-EDX, and TPR. Catalytic tests were carried out in a 2-stage catalytic reactor where pyrolysates from the first reactor flows over the catalyst placed in the second reactor. Selective formation of toluene (and other alkylated benzenes) indicates a profound selectivity towards the formation of benzene-toluene-xylene (BXT) fractions especially in the temperature range 200–400 °C. As the temperature increases, fragmentation and bimolecular reactions involving toluene leads to synthesis of unwanted PAHs, most notably azulene. Considering 3,4-altrosan as a model compound for the lignin content in date pits, governing mechanisms of HDOs, was mapped out using density functional theory (DFT) calculations. Results reported herein are expected to assist in the optimizing operational conditions that leads to the production of the valuable BXT fraction from pyrolysis of date pits.

PLP-Dependent Enzyme Methionine γ-Lyase: Insights into the Michaelis Complex from Molecular Dynamics and Free Energy Simulations.

Methionine γ-lyase (MGL) breaks down methionine, with the help of its cofactor pyridoxal-5'-phosphate (PLP), or vitamin B6. Methionine depletion is damaging for cancer cells but not normal cells, so MGL is of interest as a therapeutic protein. To increase our understanding and help engineer improved activity, we focused on the reactive, Michaelis complex between MGL, covalently bound PLP, and substrate Met. is not amenable to crystallography, as it proceeds to products. Experimental activity measurements helped exclude a mechanism that would bypass . We then used molecular dynamics and alchemical free energy simulations to elucidate its structure and dynamics. We showed that the PLP phosphate has a pKa strongly downshifted by the protein, whether Met is present or not. Met binding affects the structure surrounding the reactive atoms. With Met, the Schiff base linkage between PLP and a nearby lysine shifts from a zwitterionic, keto form to a neutral, enol form that makes it easier for Met to approach its labile, target atom. The Met ligand also stabilizes the correct orientation of the Schiff base, more strongly than in simulations without Met, and in agreement with structures in the Protein Data Bank, where the Schiff base orientation correlates with the presence or absence of a co-bound anion or substrate analogue in the active site. Overall, the Met ligand helps organize the active site for the enzyme reaction by reducing fluctuations and shifting protonation states and conformational populations.

Shell effects in fission and quasi-fission reactions

Quantum shell effects are responsible for asymmetric fission. They are also expected to affect the formation of fission fragments in quasi-fission reactions occurring in heavy-ion collisions. Systematic time-dependent Hartree-Fock simulations of 40–56Ca+176Yb collisions show that quasi-fission fragment properties share strong similarities with fragments formed in fission of the compound nuclei. This is an indication that similar shell effects are responsible for the final asymmtery in both mechanisms.

Association Between Apolipoprotein C-3 SstⅠ Polymorphism and Serum Lipids in Patients With Gestational Diabetes Mellitus

To investigate the apolipoprotein C-3 (APOC3) gene Sst Ⅰ polymorphism and its relationship with changes in serum lipids in patients with gestational diabetes mellitus (GDM). A total of 630 pregnant women with GDM and 1027 normal pregnant controls were covered in the study. The genotype and allele frequencies of APOC3 Sst Ⅰ polymorphism were analyzed by polymerase chain reaction and restriction fragment length polymorphism (PCR-RFLP). Total cholesterol (TC), triglyceride (TG), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), and glucose (Glu) were measured by enzymatic methods. Plasma insulin (INS) was measured by chemiluminescence. Apolipoproteins A 1 (apoA1) and B (apoB) levels were measured by turbidimetric immunoassay. The allele frequencies of S1 and S2 of the APOC3 polymorphism at the SstⅠ locus were 0.704 and 0.296 in the GDM group and 0.721 and 0.279 in the control group, respectively. There was no significant difference in genotype frequency and allele frequency of APOC3 Sst Ⅰ polymorphism between the GDM and the control groups ( P>0.05). In the GDM group, those with S2S2 and S1S2 genotypes had higher plasma HDL-C levels and lower atherogenic index (AI) values than those with S1S1 genotype did, with the differences being statistically significant (all P<0.05). GDM patients were then divided into obesity and non-obesity subgroups. Further subgroup analysis showed that the association of APOC3 genotype with changes in HDL-C levels was observed only in obese GDM patients, while the association of APOC3 genotype with changes in AI values was observed in both obese and nonobese patients. In addition, in obese GDM patients, those with S2S2 genotype had significantly higher plasma TG levels than those with S1S1 and S1S2 genotypes did ( P<0.05 and P<0.01, respectively). In non-obese GDM patients, those with S2S2 genotype had significantly lower apoB/apoA1 ratio than S2S2 carriers did ( P<0.05). No genotype-related effect on lipid and apolipoprotein variations was evident in the normal controls. APOC3 Sst Ⅰ polymorphism in GDM patients is associated with HDL-C and TG levels as well as AI value and apoB/apoA1 ratio. The changes in lipid levels and apolipoprotein ratio showed BMI-dependent features. However, association between polymorphism at the locus and the development of GDM was not observed.

Association of Cytochrome P450 2E1 and N-Acetyltransferase 2 Genotypes with Serum Isoniazid Level and Anti-Tuberculosis Drug-Induced Hepatotoxicity: A Cross-Sectional Study.

Anti-tuberculosis drug-induced hepatotoxicity can result from genetic polymorphism of the isoniazid (INH) metabolizing enzyme. This study aimed to determine the effect of genetic polymorphism of N-acetyltransferase 2 (NAT2) and cytochrome P450 2E1 (CYP2E1) genes on serum isoniazid level and drug-induced hepatotoxicity. A cross-sectional study was conducted on 120 patients (with and without hepatotoxicity) with pulmonary tuberculosis from June 2019 to April 2022 in Tehran (Iran). High-performance liquid chromatography was used to measure the serum concentration of INH and acetylisoniazid (AcINH). NAT2 and CYP2E1 genotypes were determined using polymerase chain reaction and restriction fragment length polymorphism methods. Data were analyzed using SPSS software (version 22.0) with independent two-sample t test, Chi square test, or Fisher's exact test. P<0.05 was considered statistically significant. A total of 40 patients showed hepatotoxicity. The risk of anti-tuberculosis drug-induced hepatotoxicity was significantly higher in patients who are slow acetylator (SA) phenotype than in rapid or intermediate acetylator (P<0.001). NAT2*4/*4 genotypes were not found in patients with hepatotoxicity. The frequency of NAT2*5 and NAT2*6 haplotypes and serum INH concentration was significantly higher in patients with hepatotoxicity than in those without (P=0.003, P<0.001, and P<0.001, respectively). NAT2*4 haplotype was correlated with protection against hepatotoxicity. A combination of SA and CYP2E1 C1/C1 genotype was significantly associated with hepatotoxicity (P<0.001). Hepatotoxicity in Iranian patients with tuberculosis was confirmed due to the presence of NAT2 SA polymorphism. Determining NAT2 and CYP2E1 genotypes and/or INH concentration can be a valuable tool to identify patients susceptible to hepatotoxicity.

Prevalence of PAI-1 675 4G/5G and ACE I/D polymorphic variants in women with recurrent pregnancy losses

Aim. The present study aimed to assess the distribution of inherited risk factors of thrombophilia among women with RPL. To determine the frequency and distribution of alleles and genotypes of polymorphic loci PAI-1 6754G/5G and ACE I/D among women with RPL. Methods. The study was carried out in a group of 97 women (57 controls and 40 women with RPL). Polymerase chain reaction and restriction fragment length polymorphism (RFLP) were used to identify the polymorphisms. Results. The frequency of 4G allele of PAI-1 675 5G/4G locus was more frequent in the group of women with RPL – 67 %, compared to 54 % in the control group. It was established that the presence of the 4G allele increases the risk of RPL by almost 2 times (Р = 0.01). In the group of women with RPL the frequency of carriers of DD genotype and D allele of ACE gene was higher than in the control group (31 % vs. 19 %), but no significant differences were found. The frequency of women with a combination of 4G4G and DD genotypes of the two studied loci was 16.6 % in the group with RPL versus 2.3 % in the control group. It was shown that the presence of homozygotes for two alleles 4G of the PAI-1 gene and D of the ACE gene leads to an 8-fold increased risk of RPL (OR = 8.6, CI: 0.9841-75.154, P = 0.04). Conclusions. Significance of PAI-1 675 4G/5G and ACE I/D polymorphic variants, especially in combination, in the predisposition to RPL was established.

Endothelial Nitric Oxide Synthase T-786C and G-894T Gene Polymorphisms: A Risk Assessment of Coronary Heart Disease.

The polymorphism of the endothelial nitric oxide synthase (eNOS) gene is thought to enhance the risk of coronary heart disease (CHD). The most protruding reason for endothelial dysfunction is the diminished production of NO. In the eNOS encoding gene, a number of mutations were associated with decreased NO effect promoting the presence of CHD. This study aims to look at the role of polymorphisms in the eNOS genes G-894T and T-786C in young South Indians. From January 2022 to May 2022, 91 angiographically proven CHD subjects attending the Department of Cardiology and Medicine and 91 controls from a master health checkup in the age group of 45 years participated in this observational cross-sectional study at SRM Medical College Hospital and Research Centre in Chennai, Tamil Nadu, India. Overnight fasting plasma samples were taken for analysis of the lipid profile as well as NO by Griess reaction utilizing an enzyme-linked immunosorbent assay (ELISA) technique. Polymerase chain reaction (PCR) and restricted fragment length polymorphism (RFLP) were used to amplify the T-786C and G-894T eNOS genes. When compared to controls, the mean level of serum NO in CHD patients was considerably lower. For eNOS T-786C polymorphism, the distribution of TC genotype (p = 0.017), odds (OD) ratio = 2.1, CC genotype (p = 0.011), OD ratio = 3.75, and minor C allele frequency (p = 0.001). And for eNOS G-894T polymorphism, the distribution of GT genotype (p = 0.01), TT genotype (p =0.02) with OD ratio and minor T allele frequency (p = 0.002) with OD ratio = 1.07 and 0.83. Our study concludes that the polymorphism of eNOS T-786C and G-894T genes may be the main causative association for the presence of CHD. How to cite this article: Jaishankar T, Shivasekar M, Vinodhini VM. Endothelial Nitric Oxide Synthase T-786C and G-894T Gene Polymorphisms: A Risk Assessment of Coronary Heart Disease. J Assoc Physicians India 2023;71(9):45-50.

Toward a correct treatment of core properties with local hybrid functionals.

In local hybrid functionals (LHs), a local mixing function (LMF) determines the position-dependent exact-exchange admixture. We report new LHs that focus on an improvement of the LMF in the core region while retaining or partly improving upon the high accuracy in the valence region exhibited by the LH20t functional. The suggested new pt-LMFs are based on a Padé form and modify the previously used ratio between von Weizsäcker and Kohn-Sham local kinetic energies by different powers of the density to enable flexibly improved approximations to the correct high-density and iso-orbital limits relevant for the innermost core region. Using TDDFT calculations for a set of K-shell core excitations of second- and third-period systems including accurate state-of-the-art relativistic orbital corrections, the core part of the LMF is optimized, while the valence part is optimized as previously reported for test sets of atomization energies and reaction barriers (Haasler et al., J Chem Theory Comput 2020, 16, 5645). The LHs are completed by a calibration function that minimizes spurious nondynamical correlation effects caused by the gauge ambiguities of exchange-energy densities, as well as by B95c meta-GGA correlation. The resulting LH23ptfunctional relates to the previous LH20t functional but specifically improves upon the core region.

Relationship between bladder cancer and polymorphisms of OX40 (rs17568) and OX40L (rs1234313) genes in a Turkish population

The aim of this study was to investigate a possible association between the variations and effects of gene changes in the OX40/OX40L pathway and the risk of developing bladder cancer in a Turkish population. The study included 104 patients with bladder cancer and 97 healthy individuals. The distribution of OX40 (rs17568) and OX40L (rs1234313) polymorphisms was evaluated by polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP). The genotype distributions of OX40 rs17568 regions showed non-significant differences between the patient and control groups (p = 0.256). No difference was also found in T2 invasive tumours, high, and low-grade tumours. The genotype distributions of the OX40L rs1234313 region were significantly different between the patient and control groups (p = 0.023). The frequency of the GG genotype and homozygous GG/AA genotypes was higher among the patients than in the control group, and the difference was significant (for GG genotype: OR 0.462; 95% CI 0.255–0.835; p = 0.010; for GG/AA genotype: OR 0.456 (0.257–0.808; p: 0.007). The OX40L A allele (AA/AG) had higher frequency in T2 invasive bladder cancer patients than in those with T1 and Ta (p = 0.028). There was no statistically significant difference in the OX40L genotype distributions among the graded tumour groups (p = 0.689). The results indicate that the rs1234313 A/G gene polymorphism may contribute to the development of bladder cancer in this Turkish population. Further observations in a larger cohort need to confirm this suggestion.

(Invited) Decoupled Water Splitting for Green Hydrogen Production: Reshaping Water Electrolysis

Green hydrogen produced by splitting water molecules into hydrogen and oxygen using electricity from renewable energy sources is essential to reduce CO2 emissions, especially in hard-to-abate industrial sectors such as steelmaking and ammonia production. It is a critical component in the energy transition to fight climate change. The present technologies for green hydrogen production are alkaline and polymer electrolyte membrane water electrolysis. One thing in common to these technologies is the coupling between the hydrogen and oxygen evolution reactions (HER and OER, respectively), where both reactions occur concurrently in the same electrolytic cell. Therefore, a membrane or diaphragm divides the cell into two compartments to avoid hazardous H2/O2 mixing. This membrane architecture complicates the electrolyzers construction by adding gaskets and compression sealing to prevent H2/O2 crossover. This adds substantial costs and limits operation at high pressures and low-purity water. In addition, substantial energy losses, mostly due to the difficult OER, increase the cost of energy in this energy intensive technology. These drawbacks give rise to high cost of green hydrogen.To overcome these challenges, we developed alternative processes that decouple the generation of hydrogen and oxygen into two consecutive stages (time separation),1 or two cells (space separation),2 avoiding the need for membrane and sealing. In addition, we divided the OER, a difficult electrochemical reaction that requires four electrons and protons to generate an oxygen molecule on a single atomic reaction site, into two sub-reactions that occur on four sites, thereby enabling facile reactions and reducing the energy losses in water electrolysis. An ultrahigh efficiency of nearly 99% was demonstrated at lab scale,2 and we expect reaching above 90% at system scale. To bring this breakthrough process to reality we established H2Pro, an Israeli startup company that aims to produce green hydrogen at $1/kg by the end of this decade, based on our invention.3 Landman et al., Photoelectrochemical water splitting in separate oxygen and hydrogen cells, Nature Materials 16, 646–651 (2017).Dotan et al., Decoupled hydrogen and oxygen evolution by a two-step electrochemical – chemical cycle for efficient overall water splitting, Nature Energy 4, 786–795 (2019).Rothschild et al., Methods and system for hydrogen production by water electrolysis, United States Patent No. 2020/0040467 A1 (2020).

Indirect Electrocatalysis S─N/S─S Bond Construction by Robust Polyoxometalate Based Foams.

Indirect electrocatalytic conversion of cheap organic raw materials via the activation of S─H and N─H bonds into the value-added S─N/S─S bonds chemicals for industrial rubber production is a promising strategy to realize the atomic economic reaction, during which the kinetic inhibition that is associated with the electron transfer at the electrode/electrolyte interface in traditional direct electrocatalysis can be eliminated to achieve higher performance. In this work, a series of di-copper-substituted phosphotungstatebased foams (PW10 Cu2 @CMC) are fabricated with tunable loadings (17 to 44wt%), which can be successfully applied in indirect electrocatalytic syntheses of sulfenamides and disulfides. Specifically, the optimal PW10 Cu2 @CMC (44wt%) exhibits excellent electrocatalytic performance for the construction of S─N/S─S bonds (yields up to 99%) coupling with the efficient production of H2 (≈50µmolg-1 h-1 ). Remarkably, it enables the scale-up production (≈14.4g in a batch experiment) and the obtained products can serve as rubber vulcanization accelerators with superior properties to traditional industrial rubber additives in real industrial processes. This powerful catalysis system that can simultaneously produce rubber vulcanization accelerator and H2 may inaugurate a new electrocatalytic avenue to explore polyoxometalate-based foam catalysts in electrocatalysis field.

Prevalence and molecular characterization of Cryptosporidium spp. in dairy cattle in Central Inner Mongolia, Northern China

BackgroundCryptosporidium is a gastrointestinal protozoan that widely exists in nature, it is an established zoonotic pathogen. Infected cattle are considered to be associated with cryptosporidiosis outbreaks in humans. In the present study, we aimed to assess the prevalence and species distribution of Cryptosporidium in dairy cattle in Central Inner Mongolia.MethodsWe focused on the small subunit ribosomal RNA gene (SSU rRNA) of Cryptosporidium and 60-kDa glycoprotein gene (gp60) of Cryptosporidium parvum. We collected 505 dairy cattle manure samples from 6 sampling sites in Inner Mongolia in 2021; the samples were divided into 4 groups based on age. DNA extraction, polymerase chain reaction (PCR), sequence analysis, and restriction fragment length polymorphism (RFLP) using SspI and MboII restriction endonucleases were performed. RFLP analysis was performed to determine the prevalence and species distribution of Cryptosporidium.ResultsSSU rRNA PCR revealed that the overall prevalence of Cryptosporidium infection was 29.90% (151/505), with a prevalence of 37.67% (55/146) and 26.74% (96/359) in diarrheal and nondiarrheal samples, respectively; these differences were significant. The overall prevalence of Cryptosporidium infection at the 6 sampling sites ranged from 0 to 47.06% and that among the 4 age groups ranged from 18.50 to 43.81%. SSU rRNA sequence analysis and RFLP analysis revealed the presence of 4 Cryptosporidium species, namely, C. bovis (44.37%), C. andersoni (35.10%), C. ryanae (21.85%), and C. parvum (11.92%), along with a mixed infection involving two or three Cryptosporidium species. Cryptosporidium bovis or C. andersoni was the most common cause of infection in the four age groups. The subtype of C. parvum was successfully identified as IIdA via gp60 analysis; all isolates were identified as the subtype IIdA19G1.ConclusionsTo the best of our knowledge, this is the first report of dairy cattle infected with four Cryptosporidium species in Inner Mongolia, China, along with a mixed infection involving two or three Cryptosporidium species, with C. bovis and C. andersoni as the dominant species. Moreover, this is the first study to identify C. parvum subtype IIdA19G1 in cattle in Inner Mongolia. Our study findings provide detailed information on molecular epidemiological investigation of bovine cryptosporidiosis in Inner Mongolia, suggesting that dairy cattle in this region are at risk of transmitting cryptosporidiosis to humans.

Loss of Oxygen Atoms on Well-Oxidized Cobalt by Heterogeneous Surface Recombination.

Calorimetry is a commonly used method in plasma characterization, but the accuracy of the method is tied to the accuracy of the recombination coefficient, which in turn depends on a number of surface effects. Surface effects also govern the kinetics in advanced methods such as atomic layer oxidation of inorganic materials and functionalization of organic materials. The flux of the reactive oxygen atoms for the controlled oxidation of such materials depends on the recombination coefficient of materials placed into the reaction chamber, which in turn depends on the surface morphology, temperature, and pressure in the processing chamber. The recombination coefficient of a well-oxidized cobalt surface was studied systematically in a range of temperatures from 300 to 800 K and pressures from 40 to 200 Pa. The coefficient increased monotonously with decreasing pressure and increasing temperature. The lowest value was about 0.05, and the highest was about 0.30. These values were measured for cobalt foils previously oxidized with oxygen plasma at the temperature of 1300 K. The oxidation caused a rich morphology with an average roughness as deduced from atomic force images of 0.9 µm. The results were compared with literature data, and the discrepancy between results reported by different authors was explained by taking into account the peculiarities of their experimental conditions.

Temperature‐dependent kinetics of the gas‐phase reactions of Cl atoms with nopinone, ketolimonene, and myrtenal

AbstractIn this study, the gas phase reaction of chlorine atoms with three first‐generation oxidation products of monoterpene: (myrtenal C10H14O, nopinone C9H14O, and ketolimonene C9H14O) were investigated using a relative technique method. These compounds result from the atmospheric oxidation of monoterpene compounds such as α/β – pinene and limonene. Experiments were performed at temperature range 298–353 K and atmospheric pressure in synthetic air bath gas. Cl atoms were generated by UV photolysis of dichloride (Cl2). The reaction was followed using a proton‐transfer reaction mass spectrometer (PTR‐MS) and/or Fourier‐transform infrared spectroscopy (FTIR) to monitor the concentrations of the investigated species simultaneous with several reference compounds as a function of time. The rate constants were obtained and the Arrhenius expressions (cm3 molecule−1 s−1) obtained were established over the temperature range of 298–353 K:knopinone + Cl = (5.0 ± 1.2) × 10−10 exp ( − (406 ± 78) /T)kketolimonene + Cl = (8.88 ± 1.3) × 10−10 exp( − (246 ± 46)/T)kmyrtenal + Cl = (13.5 ± 6.4) × 10−10 exp( − (535 ± 153)/T)Based on rate constants, the atmospheric lifetimes (τ) of targeted compounds with respect to reaction with chlorine atoms were estimated and expected to be less than 1 day. There results led to conclude that the reaction with chlorine atoms can be an effective tropospheric loss pathway mainly in regions presenting relatively high chlorine concentrations.

Investigation of typical heterocyclic fragment structures and reaction characteristics in oil shale using density functional theory

Investigation of typical heterocyclic fragment structures and reaction characteristics in oil shale using density functional theory

Hydroxy esters atmospheric degradation: OH and Cl reactivity, products distribution and fate of the alkoxy radicals formed

Kinetic studies of the reaction of ethyl glycolate HOCH2C(O)OCH2CH3 with OH radicals (kOH) and Cl atoms (kCl) have been conducted by the relative method using a glass atmospheric reactor by “in situ” Fourier Transform Infrared (FTIR) and Gas Chromatography equipped with flame ionization detection by Solid Phase Micro Extraction (GC-FID/SPME) at room temperature and atmospheric pressure. The following relative rate coefficients were determined using several reference compounds and two different techniques: kEG + OH-FTIR = (4.36 ± 1.21) × 10−12; kEG + OH-GC-FID= (3.90 ± 0.74) × 10−12; and kEG + Cl-GC-FID= (6.40 ± 0.72) × 10−11 all values in units of cm3.molecule−1.s−1. Complementary product studies were performed under comparable conditions to the kinetic tests, in order to identify the reaction products and to postulate their tropospheric oxidation mechanisms. The reaction of OH radicals and Cl atoms with ethyl glycolate initiates via H-atom abstraction from alkyl groups of the molecule. Formic acid was positively identified as a reaction product by FTIR. On the other hand, formaldehyde, acetaldehyde, glycolic acid; and formic acid were identified by the GC-MS technique. The Structure–Activity Relationship, (SAR) calculations were also implemented to estimate the more favorable reaction pathways and compare them with the products identified. Tropospheric lifetimes of τOH = 34 h and τCl = 5.5 days were estimated to determine how these investigated reactions might affect the air quality. In this sense, average ozone production of [O3] = 0.75 and a Photochemical Ozone Creation Potential, POCP, of 38 were calculated for the hydroxyl ester studied.

IR Spectra of Entrance and Exit Channels of Methane Molecule and Oxygen Atom Reaction at MP2 Theory

IR spectra of entrance and exit channels of methane and radical oxygen reaction are predicted in the ground state energy. Ab initio calculations at perturbation theory (MP2) with Dunning correction- consistent basis set (aug-cc-pVDZ) have been used. The calculations predicted structures, vibrational frequencies and potential energy surface. Three van der Waals minima from three adiabatic potential energy surfaces have been predicted in entrance and exit channels. Vibration frequency of 3209 cm-1 and 3212 cm-1 of C-H stretching in entrance structures are predicted while O-H vibrational frequency is predicted to be at 3673 cm-1 in the other channel. The lowest energy structure in entrance channel has - 0.18 kJ/ mol minimum energy.

Photochemical radical benzylic bromination with Br2: Computational modeling of the mechanism and microkinetic

Halogenation of organic compounds is an important functionalization process for further chemical transformation and the benzylic hydrogen is reactive towards the photochemically generated Br atom. This work reports the free energy profile of the several steps of the reaction of the Br atom with toluene leading to benzyl bromide, (dibromomethyl)benzene, and (tribromomethyl)benzene using reliable theoretical B2GP-PLYP method. A detailed microkinetic analysis of the reaction rate and product distribution was also performed. Our analysis points out that polar solvent increases the reaction rate in relation to apolar one. Substitution on the aromatic ring cannot be explained by the electrophilic mechanism in an apolar medium. The reactivity of different benzylic substrates was evaluated, and we have found that the cyano electron-withdrawing group in the aromatic ring retards the reaction, while the ortho-methoxy group, and oxygen and nitrogen atoms bonded to the benzylic carbon, enhance the reaction rate.