Formation Of Cl Research Articles

Anions in laser-induced plasmas

The equation of state for plasmas containing negative atomic and molecular ions (anions) is modeled. The model is based on the assumption that all ionization processes and chemical reactions are at local thermal equilibrium and the Coulomb interaction in the plasma is described by the Debye–Huckel theory. In particular, the equation of state is obtained for plasmas containing the elements Ca, Cl, C, Si, N, and Ar. The equilibrium reaction constants are calculated using the latest experimental and ab initio data of spectroscopic constants for the molecules CaCl\(_2\), CaCl, Cl\(_2\), N\(_2\), C\(_2\), Si\(_2\), CN, SiN, SiC, and their positive and negative ions. The model is applied to laser-induced plasmas (LIPs) by including the equation of state into a fluid dynamic numerical model based on the Navier–Stokes equations describing an expansion of LIP plumes into an ambient gas as a reactive viscous flow with radiative losses. In particular, the formation of anions Cl−, C−, Si−, \( {\text{Cl}}_{2}^{ - }\), \( {\text{Si}}_{2}^{ - }\), \( {\text{C}}_{2}^{ - }\), CN−, SiC−, and SiN− in LIPs is investigated in detail.

Report on the Photochemical Induced Halogen Activation of Fecontaining Aerosols

Iron (Fe) occurs in minerals and highly saline media (e.g., sea salt aerosol, salt brines etc.) and induces photochemical processes. High salinity, low pH, and organic constituents promote the dissolution of iron, forming photosensitive complexes that are responsible for a production of gaseous Cl atoms when irradiated by sunlight. We studied the production of atomic Cl, Br and OH radicals from modeled salt pans and artificial sea-salt aerosols containing Fe(III) ions or pyrogenic Fe2O3 particles (Sicotrans Orange, BASF) at various compositions in a Teflon smog-chamber. The samples were either spread on a Teflon sheet or they were nebulized from dilute brines (most abundant particle diameter: ~0.4 μm, initial surface area: up to 3·10-2cm2cm-3) and exposed to simulated sunlight at 60-90% relative humidity. The photochemical formation of Cl, OH (and Br if possible) in the gas phase was quantified by the radical clock method resulting in time profiles of the radical-production rates and total productions. Simultaneous monitoring of the aerosol surface area enabled us to determine the initial Cl production rate per cm2 aerosol surface. Whereas no significant Cl production was detected employing a molar Cl-/Fe(III) ratio of 955, the rate increased to ~2.8·1017 atoms cm-2 s-1 (at a ratio of 101), ~4.1·1017 atoms cm-2 s-1 (at a ratio of 53) and ~1.9·1018 atoms cm-2 s-1 (at a ratio of 13). The presence of NO2 (~20 ppb) or O3 (630 ppb) in the gas phase additionally increased the Fe(III)-induced chloride activation to ~7·1018 atoms cm-2 s-1 and ~9·1018 atoms cm-2 s-1 (at a Cl-/Fe(III) ratio of 13), respectively. SO2 slightly restrained the Cl formation. Artificial sea salt aerosols doped with Fe2O3 particles (Cl-/Fetot~13) did not result in detectable Cl concentrations. However, decreasing the pH below 2 favored the dissolution of Fe and led to Cl production rates comparable to the Fe(III) experiments (~7·1018 atoms cm-2 s-1) whereas accelerating the erosion of the particles by freezing and thawing did not lead to detectable results. These observations are in accord with the speciation of the photolabile, aqueous Fe(III) complexes obtained from an equilibrium model (PHREEQC). The aerosol experiments result in much higher effective Cl production rates with ~50% of active Fe(III) in zero air, as compared to the previous salt-pan experiments in the same Teflon smog-chamber with a portion of 0.05-0.07% of active Fe(III)). This is caused by the larger active surface area of the homogeneously distributed aerosols.

Assessment of parameters influencing the electro activated water character and explanation of process mechanism

The physicochemical properties of electro activated water (EAW) are highly affected by process conditions. In this context, the effects of parameters such as brine concentration, electrolysis time and current for EAW generation have been investigated using Response Surface Methodology (RSM). The predictive model for each response had high accuracy relative to R2 values, namely, 0.85 for the oxidation reduction potential (ORP) and 0.94 for the free chlorine concentration (FCC). According to results, the brine concentration was the most significant factor that affected EAW character. Moreover, electrolysis time and brine concentration have synergetic effect on FCC. The mechanism of the EAW production was evaluated through the cyclic voltammogram (CV) of different brine concentrations on the graphite electrode. With the concentration increased anodic and cathodic peaks could be observed notably. Possible reaction pathways were evaluated on the cathode and anode sides. The formation of Cl2, O2, H2, Cl−, OH−, H+ were determined by CV measurements.

VACUUM ULTRAVIOLET LASER PHOTOION AND PULSED FIELD IONIZATION–PHOTOION STUDY OF RYDBERG SERIES OF CHLORINE ATOMS PREPARED IN THE ${}^{2}{{\rm{P}}}_{J}$ (J= 3/2 and 1/2) FINE-STRUCTURE STATES

We have measured the high-resolution vacuum ultraviolet (VUV) photoion (VUV-PI) and VUV pulsed-field ionization–photoion (VUV-PFI-PI) spectra of chlorine atoms (Cl) in the VUV energy range 103,580–105,600 cm−1 (12.842–13.093 eV) using a tunable VUV laser as the photoexcitation and photoionization source. Here, Cl atoms are prepared in the Cl(2P3/2) and Cl(2P1/2) fine-structure states by 193.3 nm laser photodissociation of chlorobenzene. The employment of VUV-PFI-PI detection has allowed the identification of Rydberg transitions that are not observed in VUV-PI measurements. More than 180 new Rydberg transition lines with principal quantum number up to n = 61 have been identified and assigned to members of nine Rydberg series originating from the neutral Cl(2P3/2) and Cl(2P1/2) fine-structure states. Two of these Rydberg series are found to converge to the Cl+(3P2), four to the Cl+(3P1), and three to the Cl+(3P0) ionization limits. Based on the convergence limits determined by least-squares fits of the observed Rydberg transitions to the modified Ritz formula, we have obtained a more precise ionization energy (IE) for the formation of the ionic Cl+(3P2) from the ground Cl(2P3/2) state to be 104,591.01 ± 0.13 cm−1. This is consistent with previous IE measurements, but has a smaller uncertainty. The analysis of the quantum defects obtained for the Rydberg transitions reveals that many high-n Rydberg transitions are perturbed.

Mechanistic Study on the Formation of Cl-/Br-/I-Trihalomethanes during Chlorination/Chloramination Combined with a Theoretical Cytotoxicity Evaluation.

Chlorination followed by chloramination can be used to mitigate the formation of potentially toxic iodinated disinfection byproducts (I-DBPs) while controlling the formation of regulated chloro-bromo-DBPs (Cl-/Br-DBPs). Water samples containing dissolved organic matter (DOM) isolates were subjected to 3 disinfection scenarios: NH2Cl, prechlorination followed by ammonia addition, and HOCl alone. A theoretical cytotoxicity evaluation was carried out based on the trihalomethanes (THMs) formed. This study demonstrates that the presence of bromide not only enhances the yield and rate of iodate formation, it also increases the formation of brominated I-THM precursors. A shift in the speciation from CHCl2I to the more toxic CHBr2I, as well as increased iodine incorporation in THMs, was observed in the presence of bromide. For low bromide concentrations, a decrease in I-THM formation and theoretical cytotoxicity was achieved only for high prechlorination times, while for high bromide concentrations, a short prechlorination time enabled the full conversion of iodide to iodate. For low DOM concentrations or DOM with low reactivity, Br-/I-THMs were preferentially formed for short prechlorination times, inducing high cytotoxicity. However, for high chlorine exposures, the cytotoxicity induced by the formation of regulated THMs might outweigh the benefit of I-THM mitigation. For high DOM concentrations or DOM with higher reactivity, mixed I-THMs were formed together with high concentrations of regulated THMs. In this case, based on the cytotoxicity of the THMs formed, the use of NH2Cl is recommended.

Photofragmentation Mechanisms of Chlorosulfonyl Isocyanate, ClSO2NCO, Excited with Synchrotron Radiation between 12 and 550 eV.

The unimolecular photofragmentation mechanisms of chlorosulfonyl isocyanate, ClSO2NCO, excited with tunable synchrotron radiation between 12 and 550 eV, were investigated by means of time-of-flight (TOF) coincidence techniques. The main fragmentation mechanism after single ionization, produced by irradiation of an effusive beam of the sample with synchrotron light in the valence electron region, occurs through the breaking of the Cl-S single bond, giving a chloride radical and a SO2NCO(+) fragment. This mechanism contrasts with the one observed for the related FSO2NCO, in which the rupture of the S-N bond originates the FSO2(+) fragment. The energies of the shallow- (S 2p, Cl 2p, and S 2s) and core-shell (C 1s, N 1s, and O 1s) electrons were determined by X-ray absorption. Transitions between these shallow and core electrons to unoccupied molecular orbitals were also observed in the total ion yield (TIY) spectra. Fourteen different fragmentation mechanisms of the doubly charged parent ion, ClSO2NCO(2+), were inferred from the bidimensional photoelectron-photoion-photoion-coincidence (PEPIPICO) spectra. The rupture of the S-N bond can evolve to form NCO(+)/SO2(•+), NCO(+)/SO(•+), or S(•+)/NCO(+) pairs of ions. The Cl-S bond breaking originates different mechanisms, Cl(+)/SO(•+), Cl(+)/S(•+), CO(•+)/S(•+), O(•+)/SO(•+), O(•+)/Cl(+), O(•+)/S(•+), C(•+)/S(•+), and C(•+)/O(•+) pairs being detected in coincidence as the final species. Another three coincidence islands can only be explained with an initial atomic rearrangement forming ClNCO(2+), ONCO(2+), and ClCO(2+), as precursors of CO(•+)/Cl(+), O(•+)/CO(•+), and C(•+)/Cl(+) pairs, respectively. The formation of Cl(•) radical is deduced from several mechanisms.

Photochemical oxidation of chloride ion by ozone in acid aqueous solution.

The experimental investigation of chloride ion oxidation under the action of ozone and ultraviolet radiation with wavelength 254 nm in the bulk of acid aqueous solution at pH 0-2 has been performed. Processes of chloride oxidation in these conditions are the same as the chemical reactions in the system O3 - OH - Cl(-)(aq). Despite its importance in the environment and for ozone-based water treatment, this reaction system has not been previously investigated in the bulk solution. The end products are chlorate ion ClO3(-) and molecular chlorine Cl2. The ions of trivalent iron have been shown to be catalysts of Cl(-) oxidation. The dependencies of the products formation rates on the concentrations of O3 and H(+) have been studied. The chemical mechanism of Cl(-) oxidation and Cl2 emission and ClO3(-) formation has been proposed. According to the mechanism, the dominant primary process of chloride oxidation represents the complex interaction with hydroxyl radical OH with the formation of Cl2(-) anion-radical intermediate. OH radical is generated on ozone photolysis in aqueous solution. The key subsequent processes are the reactions Cl2(-) + O3 → ClO + O2 + Cl(-) and ClO + H2O2 → HOCl + HO2. Until the present time, they have not been taken into consideration on mechanistic description and modelling of Cl(-) oxidation. The final products are formed via the reactions 2ClO → Cl2O2, Cl2O2 + H2O → 2H(+) + Cl(-) + ClO3(-) and HOCl + H(+) + Cl(-) ⇄ H2O + Cl2. Some portion of chloride is oxidized directly by O3 molecule with the formation of molecular chlorine in the end.

Investigation of suppressor polyethylene glycol dodecyl ether on electroplated Cu filling by electrochemical method

In this paper, the use of polyethylene glycol dodecyl ether (POE) with a molecular weight of 1200 (POE-1200) as a suppressor for bottom-up electroplated copper filling of microvias was investigated. Galvanostatic measurement indicated that POE-1200 had much stronger suppression for Cu electrodeposition than PEG-8000 (polyethylene glycol with a molecular weight of 8000) and EPE-8000 (triblock copolymers of ethylene oxide–propylene oxide–ethylene oxide with a molecular weight of 8000). The strong synergistic suppression between POE-1200 and Cl− led to a very thin surface thickness and excellent filling performance of microvias. The cross-sectional observations of the microvias after electroplated confirmed that changing the POE-1200 concentration from 20 to 700 ppm had little effect on the filling performance because of an unchanged positive potential difference. The adsorption strength of POE-1200 on the cathode surface was enhanced greatly only in the presence of Cl− , attributing to a formation of Cl− –Cu+–POE-1200 complex. The critical adsorption concentration of Cl− and POE-1200 to form a saturated barrier film on the electrode surface was studied by Cu stripping peaks of cyclic voltammetry curves. In addition, the relationship between the saturated barrier of Cl− –Cu+–POE-1200 complex and the filling performance has been proposed.

Autotrophic perchlorate reduction kinetics of a microbial consortium using elemental sulfur as an electron donor.

The perchlorate reduction kinetic parameters of a microbial consortium using elemental sulfur (S(0)) as an electron donor were investigated in batch experiments. Standard Monod substrate utilization and biomass accumulation models were employed to fit the experimental data for microbial perchlorate reduction. The maximum observed yield coefficient for the microbial consortium was 0.19 mg dry weight (DW) mg(-1) ClO4 (-), suggesting that the microbial consortium had a slow growth rate using S(0) as the electron donor. The maximum specific substrate utilization rate (q max) and half saturation constant (K s) for microbial perchlorate reduction were 0.14 mg ClO4 (-) mg(-1) DW day(-1) and 5.71 mg L(-1), respectively, which indicated that the microbial consortium could effectively utilize perchlorate as an electron acceptor. The variation of q max with pH was described well by using a Gaussian peak equation, and the maximal value of q max was obtained at pH 6.7. The presence of nitrate in perchlorate-contaminated water delayed the onset of sulfur autotrophic perchlorate reduction. The modified Gompertz equation could adequately describe the formation of Cl(-) and SO4(2-) during the process of sulfur autotrophic perchlorate reduction. The SO4(2-) production exceeded the theoretical SO4(2-) production due to S(0) disproportionation. The kinetic parameters for microbial perchlorate reduction are essential to design biological treatment systems, as well as to predict and evaluate their performance.

Using XANES to obtain mechanistic information for the hydrolysis of CuCl2 and the decomposition of Cu2OCl2 in the thermochemical Cu–Cl cycle for H2 production

The Advanced Photon Source (APS) at Argonne National Laboratory was used to investigate the progress of two of the reactions of the copper–chlorine cycle for production of hydrogen in situ by studying the evolution of the solid Cu species, using X-ray absorption near edge structure (XANES) spectroscopy. The hydrolysis of CuCl2 (2 CuCl2 + H2O → Cu2OCl2 + 2 HCl) was studied under low and high steam-to-copper ratios from 423 to 725 K, and the decomposition of Cu2OCl2 (Cu2OCl2 → 2 CuCl + ½ O2) in dry and humidified nitrogen up to 750 K. This study showed that the formation of Cu2OCl2 by hydrolysis of CuCl2 is more favorable under low steam-to-copper mole ratios and it reaches a maximum around 675 K. Over this limit, the formation of CuO and Cl2 as reaction byproducts starts to be noticeable. The same reaction byproducts were observed to form under all of the other experimental conditions and at temperatures as low as 635 K. The results from the decomposition studied by XANES are in very good agreement with calorimetric studies (TG/DSC) and they confirm that the formation of Cl2 takes place in the early stages of the decomposition of Cu2OCl2. To the best of our knowledge, this is the first time that the XANES spectrum of a Cu2OCl2 standard has been reported, since in previous studies Cu2OCl2 was always a reaction intermediate.

Novel determinants of the neuronal Cl(-) concentration.

It is now a well-accepted view that cation-driven Cl(-) transporters in neurons are involved in determining the intracellular Cl(-) concentration. In the present review, we propose that additional factors, which are often overlooked, contribute substantially to the Cl(-) gradient across neuronal membranes. After briefly discussing the data supporting and opposing the role of cation-chloride cotransporters in regulating Cl(-), we examine the participation of the following factors in the formation of the transmembrane Cl(-) gradient: (i)fixed 'Donnan' charges inside and outside the cell; (ii)the properties of water (free vs. bound); and (iii)water transport through the cotransporters. We demonstrate a steep relationship between intracellular Cl(-) and the concentration of fixed negative charges on macromolecules. We show that in the absence of water transport through the K(+)-Cl(-) cotransporter, a large osmotic gradient builds at concentrations below or above a set value of 'Donnan' charges, and show that at any value of these fixed charges, the reversal potential for Cl(-) equates that of K(+). When the movement of water across the membrane is a source of free energy, it is sufficient to modify the movement of Cl(-) through the cotransporter. In this scenario, the reversal potential for Cl(-) does not closely follow that of K(+). Furthermore, our simulations demonstrate that small differences in the availability of freely diffusible water between inside and outside the cell greatly affect the Cl(-) reversal potential, particularly when osmolar transmembrane gradients are minimized, for example by idiogenic osmoles. We also establish that the presence of extracellular charges has little effect on the chloride reversal potential, but greatly affects the effective inhibitory conductance for Cl(-). In conclusion, our theoretical analysis of the presence of fixed anionic charges and water bound on macromolecules inside and outside the cell greatly impacts both Cl(-) gradient and Cl(-) conductance across neuronal membranes.

Using corona discharge-ion mobility spectrometry for detection of 2,4,6-Trichloroanisole

In this work possible application of the corona discharge-ion mobility spectrometer (CD-IMS) for detection of 2,4,6-Trichloroanisole (TCA) has been investigated. We applied CD-IMS interfaced with orthogonal acceleration time of flight mass spectrometer (CD-IMS-oaTOF) to study the ion processes within the CD-IMS technique. The CD-IMS instrument was operated in two modes, (i) standard and (ii) reverse flow modes resulting in different chemical ionisation schemes by NO3−(HNO3)n (n=0,1,2) and O2−(H2O)n (n=0,1,2), respectively. The O2−(H2O)n ionisation was associated with formation of Cl− and (TCA–CH3)− ions from TCA. The NO3−(HNO3)n ionisation, resulted in formation of NO3−(HNO3)(TCA–Cl) adduct ions. Limit of detection (LOD) for TCA was determined in gas (100ppb) and solid phases (150ng).

Ground state surface formation of Cl2 in the dissociation of CCl4 and CHCl3 and comparisons with Br species

The formation of molecular chlorine from the ground state dissociation of CCl4 and CHCl3 was investigated at the M06, MP2 and CCSD(T) levels of theory, all using the cc-pVTZ basis set. All levels of theory showed the presence of two transition states and an ion-pair isomer intermediate. The presence of the isomer in the dissociation pathway is in agreement with previous studies on the ground state dissociation of similar halocarbons.

Characteristics of estrous cycles in gilts treated with gonadotropins after estrus or treatment with a progestogen

A combination of eCG (400 IU) and hCG (200 IU) (P.G. 600; Merck Animal Health, Summit, NJ, USA) stimulates puberty in gilts, but variation in the estrual response exists among farms. We hypothesized that some of the variability is a consequence of gilts that have commenced cycling being inadvertently treated. The objective of experiment 1 was to determine the effect of intramuscular (im) P.G. 600 on estrous cycles in sexually mature gilts. Gilts in treatment 1 (n = 16) received P.G. 600 at the onset of daily boar exposure. Gilts in treatments 2 to 5 (n = 16 per treatment) were allowed to express a natural first estrus and were then treated with P.G. 600 during the first estrous cycle as follows: treatment 2 at Day 6, treatment 3 at Day 12, and treatment 4 at Day 18 of the estrous cycle. Treatment 5 gilts received no P.G. 600. The proportion of gilts displaying a normal estrous cycle (18–24 days) was greater (P < 0.05) for treatments 4 (100%) and 5 (100%) compared with treatments 1 (73.3%) and 3 (60%), with treatment 2 having a value (87.5%) that was not different from the other groups. For treatment 3, 33% of gilts displayed an increased interestrus interval that averaged 32.5 days. Concentrations of progesterone remained elevated 20 days after the onset of first estrus in treatment 3 gilts, which supports the concept that P.G. 600 administered at Day 12 of the estrous cycle induced follicular growth, ovulation, and formation of CL that functioned for approximately 15 days, increasing the length of the estrous cycle. It is common for swine producers to have groups of replacement gilts that include both cycling and prepubertal animals, or individuals, the cycling status of which is unknown. The objective of experiment 2 was to evaluate a system using a combination of a progestogen (Matrix; Merck Animal Health) and P.G. 600 to synchronize estrus in replacement gilts. Crossbred gilts, assumed to be a mix of cycling and prepubertal females, were allocated to one of four treatments (n = 12 per treatment): treatment 1, Matrix (15 mg/day) fed for 14 days and im P.G. 600 24 hours after the last feeding of Matrix; treatment 2, Matrix for 7 days and P.G. 600; treatment 3, P.G. 600 only; and treatment 4, im water only. The percentage of gilts in estrus within 7 days after im treatment was the greatest (P < 0.02) and days to estrus the least (P < 0.05) for gilts receiving Matrix for 14 days and P.G. 600 (treatment 1, 91.7% and 5.4 ± 1.9 days; treatment 2, 50% and 9.2 ± 2.0 days; treatment 3, 33% and 13.8 ± 2.1 days; and treatment 4, 50% and 9.1 ± 1.9 days). The results of these experiments suggest that P.G. 600 administered to gilts that have already obtained puberty may cause abnormal estrous cycles and demonstrate to swine producers the need to correctly classify replacement gilts as prepubertal or cycling before administering the product. The use of Matrix and P.G. 600 in combination has potential as an effective strategy for synchronizing estrus in a mix of prepubertal and mature, cycling gilts.

Cuprous Ion As An Accelerant of Copper Damascene Electrodeposition

Free cuprous formed inside trench accelerates trench via bottom. A drastic increase in current has been measured with N2 bubbling by initially dissolving the copper of the trench bottom electrode. The current densities increase with the narrower trench bottom electrode width. With O2 bubbling, the currents show a very low value and no difference in the trench bottom electrode width. These drastic differences in current densities with the O2 gas concentration in the electrolyte must be caused by the cuprous complex formed in the trench of the trench bottom electrode. The cuprous complex is free and not adsorbed by the electrode. For the basic bath with only Cl-, the current shows a marked increase. Cl- is an important additive for the acceleration, and the acceleration must be related to the free cuprous complex and electron bridge formation of Cl-. The constant potential measurements without dissolving the copper electrode, also, show that the free cuprous complex formed through electrodeposition is the accelerant.

Ion mobility spectrometry–mass spectrometry studies of ion processes in air at atmospheric pressure and their application to thermal desorption of 2,4,6-trinitrotoluene

In this study we have investigated the negative reactant ion formation in a negative corona discharge (CD) using the corona discharge ion mobility spectrometry orthogonal acceleration time-of-flight (CD-IMS-oaTOF) technique. The reactant ions were formed in the CD operating in the reverse gas flow mode at an elevated temperature of 363.5 K in synthetic and ambient air. Under these conditions mainly and their clusters were formed. We have also studied the influence of CCl4 admixture to air (dopant gas) on the composition of the reactant ions, which resulted in the formation of Cl− and its clusters with a reduced ion mobility of 3.05 cm2 V−1 s−1 as a major reactant ion peak. Additional IMS peaks with reduced ion mobilities of 2.49, 2.25 and 2.03 cm2 V−1 s−1 were detected, and Cl− · (NO2) and Cl− · (NO)n(n = 2, 3) anions were identified. The negative reactant ions were used to detect 2,4,6 trinitrotoluene (TNT) using the thermal desorption (TD) technique using a CD-IMS instrument. Using TD sampling and a negative CD ion source doped by CCl4 we have achieved a limit of detection of 350 pg for direct surface analysis of TNT.

Behavior of Cuprous Intermediate in Copper Damascene Electrodeposition

Free cuprous formed inside a trench accelerates the trench via bottom. A drastic increase in current has been measured with N2 bubbling by initially dissolving the trench bottom copper electrode. This increases with the narrower trench bottom width. With O2 bubbling, however, this shows a very low current. These differences in current densities with the O2 gas concentration in the electrolyte must be caused by the formed SPS and cuprous complex. The SPS and cuprous complex is free and not adsorbing on the electrode. For the basic bath with only Cl − , the current shows a marked increase, which is related to the electron bridge formation of Cl − .

Investigating the α-Effect in Gas-Phase SN2 Reactions of Microsolvated Anions

The α-effect-enhanced reactivity of nucleophiles with a lone-pair adjacent to the attacking center-was recently demonstrated for gas-phase S(N)2 reactions of HOO(-), supporting an intrinsic component of the α-effect. In the present work we explore the gas-phase reactivity of microsolvated nucleophiles in order to investigate in detail how the α-effect is influenced by solvent. We compare the gas-phase reactivity of the microsolvated α-nucleophile HOO(-)(H2O) to that of microsolvated normal alkoxy nucleophiles, RO(-)(H2O), in reaction with CH3Cl using a flowing afterglow-selected ion flow tube instrument. The results reveal enhanced reactivity of HOO(-)(H2O) and clearly demonstrate the presence of an α-effect for the microsolvated α-nucleophile. The association of the nucleophile with a single water molecule results in a larger Brønsted βnuc value than is the case for the unsolvated nucleophiles. Accordingly, the reactions of the microsolvated nucleophiles proceed through later transition states in which bond formation has progressed further. Calculations show a significant difference in solvent interaction for HOO(-) relative to the normal nucleophiles at the transition states, indicating that differential solvation may well contribute to the α-effect. The reactions of the microsolvated anions with CH3Cl can lead to formation of either the bare Cl(-) anion or the Cl(-)(H2O) cluster. The product distributions show preferential formation of the Cl(-) anion even though the formation of Cl(-)(H2O) would be favored thermodynamically. Although the structure of the HOO(-)(H2O) cluster resembles HO(-)(HOOH), we demonstrate that HOO(-) is the active nucleophile when the cluster reacts.

Influence of polar groups in binary polymer blends on positronium formation

The present work studied the role of the polar group unconjugated oxygen on the inhibition of positronium (Ps) formation in two binary blends made from a set of chosen constituent polymers with polar and weakly polar groups (nonpolar). The polymer blend samples of PVC-EVA and PVC-SAN were investigated by coincidence Doppler broadening and positron lifetime techniques. The strong polar acetate group in the EVA contributed to positron annihilation with electrons of unconjugated oxygen (-C(+)=O(-)) as revealed by the momentum distribution curves peaking around 17 P(L) (10(-3) m(0)c). The ortho-Ps intensity indicated the unconjugated oxygen shows about a 28% Ps reduction even in the presence of a strong Ps inhibiting halogen (Cl(-)). In contrast, this effect was not seen in the PVC-SAN blends since SAN contains a weakly polar (nonpolar) acrylonitrile group (C≡N). Our results indicate the chlorine of PVC in the blends is a major contributor to Ps inhibition through the formation of a (Cl(-)-e(+)) bound state but the unconjugated oxygen in EVA of the PVC-EVA blend also plays a similar, but lesser, role.

Study of local Na+ and Cl− distributions during the cut-edge corrosion of aluminum rich metal-coated steel by scanning vibrating electrode and micro-potentiometric techniques

Scanning vibrating electrode technique (SVET) and micro-potentiometric pH measurements were performed simultaneously to study the cut-edge corrosion of aluminum-rich metal-coated steel. Different areas of pH and anodic/cathodic activity were identified and the analyzed corrosion products were linked to the values of pH measured at regions of precipitation. A step further into the understanding of the corrosion mechanism in the cut-edge is based on the knowledge concerning the movement of the ions which take part in the corrosion process.Local and in situ concentration of the ions of the supporting electrolyte, 0.005M NaCl, were recorded over the cut-edge of metal-coated steel. In this frame, zinc, aluminum and zinc/aluminum metal-coated steel samples were studied by micro-potentiometry with Cl− and Na+ selective microelectrodes. Either Cl− or Na+ distribution was mapped simultaneously with monitoring current density by SVET in continuous immersion. Interesting though unexpected finding is the depletion of Cl− in anodic sites and its accumulation in cathodic sites. Along with this, an increase of Na+ concentration occurs in anodic sites and Na+ content decreases in cathodic sites over the steel. Such distribution is explained by formation of Cl− and OH− containing corrosion products and charge compensation effects. The described Cl− distribution was partly confirmed by ex situ analysis of corrosion products performed by SEM-EDX and Raman spectroscopy.