CCl4 Molecules Research Articles

Improved data analysis for molecular dynamics in liquid CCl4

Previously reported inelastic x-ray scattering spectra of a typical van der Waals molecular liquid CCl4 were reanalyzed using a generalized Langevin formalism with a memory function including a thermal and two viscoelastic relaxation processes and simple sparse modeling. The obtained excitations of longitudinal acoustic phonons show a largely positive deviation from the hydrodynamic value by about 57%, much larger than about 37% by the previously reported damped harmonic oscillator result. Such large values of fast sounds in molecular liquids larger than 15-20% of typical liquid metals are interpreted as extra energy losses for terahertz phonons by molecules' vibrational and rotational motions. The rates of the fast and slow viscoelastic relaxations in the memory function at low Q indicate large values, about 0.5 and 2 ps, which correspond to the vibrational and rotational motions of CCl4 molecules, respectively. These values are larger than those of the typical polar molecular liquid acetone, which may reflect the heavier atomic mass of CCl4. The Q dependences of the viscoelastic relaxation rates are discussed in terms of the lifetime and propagating length of the terahertz phonon oscillations. The microscopic kinematic longitudinal viscosity was obtained from the viscoelastic relaxation magnitudes and times, rapidly decreasing with Q from a macroscopic value at Q→0.

Structure of tert-butyl alcohol in carbon tetrachloride solution. Molecular dynamics simulation study

The structure of tert-butyl alcohol (TBA) solution in carbon tetrachloride (CCl4) is studied over the entire concentration range using molecular dynamics simulation (MD). It is shown that at low alcohol concentrations (within 5% molar fraction), separate small associates of TBA appear as a result of hydrogen bonding between alcohol molecules, and cyclic structures of four TBA molecules appear among these associates. With increasing concentration, the formation of hydrogen-bonded associates quickly reaches its limit corresponding to 1.7 bonds per molecule as in pure TBA. At high alcohol concentrations, both linear and cyclic associates of TBA molecules are observed with a noticeable fraction of cyclic tetramers. Using the Voronoi method, aggregates of the nearest TBA molecules are considered. The number and size of such aggregates grows rapidly with concentration due to the presence of “nuclei” formed by hydrogen bonding. At an alcohol mole fraction of 15%, a percolation cluster of TBA molecules begins to form in the solution. On the contrary, in the local environment of CCl4 molecules no significant structural rearrangements occur, only a gradual replacement of the molecules is observed upon addition of alcohol. However at low content of CCl4 in alcohol, we can see some tendency to clustering of CCl4 molecules, which may indicate on a slight solvophobic effect in this solution.

New Mechanism via Dichlorocarbene Intermediate for Activated Carbon-Mediated Reductive Dechlorination of Carbon Tetrachloride by Sulfide in Aqueous Solutions.

Although activated carbon (AC) is widely used as an adsorbent and barrier for contaminated sediment remediation, little attention has been paid to its mediation effects on reductive dechlorination of chlorinated solvents by commonly presenting sulfide. Here, we reported that highly porous, graphitized AC (250 mg L-1) suspended in deoxygenated aqueous solutions could increase the pseudo-first-order rate constant of sulfide-induced dechlorination of carbon tetrachloride (CCl4) by more than 1 order of magnitude. Carbon disulfide (CS2) was the only main product, with no production of chloroform or dichloromethane. The minimum promotion of CCl4 reduction observed with electro-conductive but nonporous graphite and a microporous but electro-insulative resin (XAD-4) indicates that graphitic carbons and micropores both play key roles in AC-mediated dechlorination of CCl4 by sulfide. The detection of dichlorocarbene (:CCl2) by free radical trapping experiments combined with the high suitability of the Langmuir-Hinshelwood model led us to propose a new mediation mechanism: CCl4 molecules adsorbed within the deep regions of AC micropores formed by graphitic carbons accept two electrons transferred from sulfide to form :CCl2, which is impeded from hydrolysis and hydrogenolysis by the hydrophobic micropore and further reacts with sulfide to generate CS2. Consistently, the production of :CCl2 was very low when AC was replaced with graphite or XAD-4. The proposed mechanism was further validated by the enhanced mediation effects of another two carbonaceous materials (template-synthesized mesoporous carbon and covalent triazine-based framework) that are electro-conductive and have well-developed micropore structures. These findings highlight the importance of pore properties of carbonaceous materials as mediators or catalysts for reductive dechlorination reactions and shed light on the development of coupled adsorption-reaction systems for remediation.

IR Spectrometric Studies of CCL4 and Ar Gas Mixtures

IR spectrometric studies were performed to examine the cryo-deposition processes and properties of thin cryo-vacuum condensate films containing a mixture of carbon tetrachloride and argon, which were obtained by physical cryo-vacuum deposition at various concentrations. The measurements were carried out in a temperature range of 11–100 K, and the pressure of the gas phase was 10–8 Torr-10–4 Torr. The film thickness in all experiments performed was d = 2 μm. The vibrational spectra of CCl4 in an argon matrix were measured in a frequency range of 400–4200 cm−1 at mixture concentrations (CCl4 + Ar) of 10–90%, 5–95%, and 1–99% and after the argon matrix underwent sublimation. Thermal desorption curves for the yield of the matrix gas (Ar) were obtained in the temperature range of 40–90 K for the (CCl4 and Ar) system. It was found that the CCl4 molecules in the Ar matrix substance underwent cryocapture. The results obtained suggest that carbon tetrachloride can be used as a matrix in low-temperature studies on self-organization processes in thin films.

Spectroscopy and kinetics of intermediates in photochemistry of xanthate Ni(S2COEt)2 complex in CCl4

The laser flash photolysis made it possible to determine the mechanism of photochemical reactions of the xanthate Ni(S2COEt)2=Ni(xan)2 complex in CCl4. Upon the excitation of Ni(xan)2 complex, several fast processes occur. In the first of them, an electron is transferred from −S2COEt = −xan ligand to Ni(II) ion with the formation of ·S2COEt=·xan radical in coordination sphere of now Ni(I) ion. Then electron is transferred from Ni(I) to CCl4 molecule located in the second coordination sphere (CCl4 is a good electron acceptor). The nascent CCl4·- anion-radical rapidly dissociates into Cl- ion and CCl3· radical. In the solvent with low dielectric constant, a negatively charged Cl- ion is incorporated into the coordination sphere of positively charged Ni+2(-xan)(·xan)+ complex with the formation of neutral primary transient [Cl-Ni2+(-S2COEt)(·S2COEt)]=[Cl-Ni2+(-xan)(·xan)] radical complex during a laser pulse (5 ns). This particle disappears in a fast reaction with the initial Nixan2 complex with the formation of [ClNi(xan)(·xan)Nixan2] dimer (rate constant 2 × 109 M−1 s−1). The dimers disappear in second-order reaction (recombination) in millisecond time range with the formation of xan2 disulfide and ClNi(xan) complex. The ClNi(xan) complexes in a slow disproportionation reaction are transformed into NiCl2 and initial Ni(xan)2 complex. Thus, the final products of Ni(xan)2 photolysis are the xan2 disulfide and NiCl2 complex insoluble in CCl4.

Heterogeneous Reactions of Methane with Cl Radicals on Large ArN Clusters.

Heterogeneous chemistry on the surfaces of atmospheric particles has a wide impact on the properties and composition of the Earth's atmosphere. In laboratory studies, clusters can represent proxies to atmospheric aerosols and help to discern the individual steps in reactions on or in aerosols. We investigate the reactivity of Cl and CCl3 radicals with methane on argon clusters using the pickup method. For radical generation, we built a new pyrolysis source partially adapting the design of radical sources that utilize the supersonic expansion into a heated silicon carbide tube. Large ArN, N̅ ≈ 110, clusters were generated in a supersonic expansion, and CH4 molecules were embedded in the clusters via a pickup process followed by the uptake of the radicals produced in the pyrolysis source. The analysis of the mass spectra recorded under different experimental conditions (i.e., with the pyrolysis ON and OFF and with only one or both reactants) allowed us to identify various products of the radical reactions on ArN. We propose a sequence of reactions based on the reaction energetics. It starts with the hydrogen abstraction from CH4 by a Cl radical resulting in HCl and CH3 followed by a halogenation step where CCl4 molecules react with the available CH3 radicals, yielding CH3Cl. By analogy, the CH3Cl enters another hydrogen abstraction by Cl, producing HCl and the CH2Cl radical, which again undergoes a halogenation step with CCl4, generating CH2Cl2. Further reaction of CH2Cl2 with Cl terminates the sequence by the production of HCl and CHCl2.

Matrix metalloproteinases are involved in the development of neurological complications in patients with Coronavirus disease 2019

BackgroundEvidence show that Matrix metalloproteinases (MMPs) have been associated with neurological complications in the viral infections. Here in the current investigation, we intended to reveal if MMPs are potentially involved in the development of neurological symptoms in the patients with Coronavirus disease 2019 (COVID-19). MethodsThe levels of MMPs, inflammatory cytokines, chemokines, and adhesion molecules were evaluated in the serum and cerebrospinal fluid (CSF) samples from 10 COVID-19 patients with neurological syndrome (NS) and 10 COVID-19 patients lacking NS. Monocytes from the CSF samples were treated with TNF-α and the secreted levels of MMPs were determined. ResultsThe frequency of monocytes were increased in the CSF samples of COVID-19 patients with NS compared to patients without NS. Levels of inflammatory cytokines IL-1β, IL-6, and TNF-α, chemokines CCL2, CCL3, CCL4, CCL7, CCL12, CXCL8, and CX3CL1, MMPs MMP-2, MMP-3, MMP-9, and MMP-12, and adhesion molecules ICAM-1, VCAM-1, and E-selectin were significantly increased in the CSF samples of COVID-19 patients with NS compared with patients without NS. Treatment of CSF-derived monocytes obtained from COVID-19 patients with NS caused increased production of MMP-2, MMP-3, MMP-9, and MMP-12. ConclusionsHigher levels of inflammatory cytokines might promote the expression of adhesion molecules on blood-CSF barrier (BCSFB), resulting in facilitation of monocyte recruitment. Increased levels of CSF chemokines might also help to the trafficking of monocytes to CSF. Inflammatory cytokines might enhance production of MMPs from monocytes, leading to disruption of BCSFB (and therefore further infiltration of inflammatory cells to CSF) in COVID-19 patients with NS.

HEPATOPROTECTIVE ACTIVITY OF MERREMIA BORNEENSIS AGAINST CARBON TETRACHLORIDE (CCl4)-INDUCED ACUTE LIVER DAMAGE IN RATS: A BIOCHEMICAL AND HISTOPATHOLOGICAL EVALUATION

Objective: The pathogenesis of various liver injuries involves oxidative damage. This research was planned to examine the effects of Mereemia borneensis extract on hepatic oxidative damage caused by carbon tetrachloride (CCl4) in rats.
 Methods: Sprague Dawley rats were exposed to M. borneensis (125 and 250 mg/kg b. wt.) once daily for 14 d followed by two doses of CCl4 (1.2 ml/kg b. wt.). After 2 w, the rats were sacrificed and hepatoprotective analysis was done.
 Results: Orally administration of CCl4 enhances serum transaminase (ALT; alanine transaminase and AST; aspartate transaminase), γ-glutamyl transpeptidase, lipid peroxidation, reduction in glutathione, catalase, glutathione reductase, glutathione peroxidase, quinone reductase and glutathione S-transferase. Pretreatment of rats with M. borneensis at 125 and 250 mg/kg body weight significantly reduced levels of ALT, AST, γ-glutamyl transpeptidase and lipid peroxidation of CCl4 treated rats. Pretreatment with M. borneensis against rats treated with CCl4, hepatic enzymatic and non-enzymatic antioxidant molecules have increased significantly. A decreased histopathological change in the liver is further evidence of the protective effect of M. borneensis.
 Conclusion: Our data suggest that M. borneensis can be a potential hepatoprotective agent in preventing or treating degenerative diseases that involve oxidative stress.

Ionization and electron capture for H+ collisions at low keV energy with CCl4 molecules

Relative total ionization cross sections and fragment target ions have been measured for proton impact on CCl4 molecules for the first time, namely associated with the formation of CCl3+, CCl2+, CCl+, Cl2+, Cl+ and C+ ions. The experiment was conducted by crossing a proton beam of 2.5 to 10 keV with a CCl4 vapor target where the fragment ions were measured employing the time of flight technique. Relative fragment cross sections were added leading to the total relative cross section. All relative cross sections seem to be independent of the collisional energy. A qualitative comparison was conducted with previous measurements of electron impact experiments. Ratios of CCl3+/CCl2+, CCl3+/CCl+, CCl3+/C+ and CCl3+/Cl+ were compared to those obtained from electron impact experiments.

Experimental study and thermodynamic modeling of CCl4 + O2 and CCl4 + N2 hydrate equilibria

Nitrogen and oxygen are the main components of air. Liquid nitrogen is an alternative to fossil fuels. However, little attention has been paid to this energy resource. Liquid oxygen is not a fuel in itself, however, it can be used as an oxidizer to run vehicles. In this respect, gas hydrate technology can be of interest, as applicable media for nitrogen/oxygen transport or nitrogen/oxygen separation. Both nitrogen and oxygen have the tendency to form hydrates, especially at high pressures, with double occupancy of the large cavities of structure sII. Thermodynamic hydrate promoters (THPs) can be used to facilitate the formation of nitrogen or oxygen hydrates at more moderate equilibrium conditions. For this purpose, CCl4 can be a potential candidate. In this contribution, hydrate equilibrium conditions for binary mixtures of nitrogen + CCl4 (50 data points) and oxygen + CCl4 (41 data points) were experimentally measured. This was done using three different experimental equipment, namely: a tensimeter, the Cailletet apparatus, and a high-pressure autoclave. A thermodynamic model, according to the van der Waals-Platteeuw (vdW-P) solid solution theory, was then employed to predict the hydrate equilibrium temperatures of the aforementioned mixtures. The fugacities of the components in the mixtures were calculated through the Peng-Robinson (PR) EoS and the classical van der Waals mixing rules. The Kihara potential model was applied to represent the guest-host interactions. The results reveal that the model has the ability to predict the hydrate equilibrium temperatures with the average absolute deviation (AAD) of 0.32 K. The fractional occupancy calculations indicate that the CCl4 molecules mostly occupy the large cages and do not enter the small cages of sII hydrates because of their size, while nitrogen and oxygen have small contributions in the filling of the large cages of sII.

The Structure of CCl5- in the Gas Phase.

The first experimental evidence of the structure of the CCl5- gas-phase anion complex is presented in conjunction with results from high-level theoretical calculations. The photoelectron spectrum of the system shows a single peak with a maximum at 4.22 eV. Coupled cluster single double (triple) detachment energies of two stable C3v ion-molecule complexes of the form Cl-···CCl4 were also determined. The first complex found features the Cl- bound linearly in a Cl-···Cl-C bonding arrangement, while the second, less stable minimum has the Cl- positioned at the face of the CCl4 molecule, midway between three chlorine atoms. The calculated detachment energy for the first complex was found to be in excellent agreement with experiment, allowing the structure of CCl5- in the gas phase to be postulated as a noncovalent Cl-···CCl4 anion complex, with the Cl- anion tethered by a typical halogen bond.

A re-assessment of the isosteric heat for CCl4 adsorption on graphite

We have carried out molecular simulations of carbon tetrachloride adsorption on graphite, in order to investigate the role of the octopole in potential models for the CCl4/graphite system, and the temperature dependence of the first-order gas-liquid transition in the first adsorbate layer. Two classes of potential model for carbon tetrachloride were considered: the first has 5 LJ sites and the second includes five partial charges to model the leading octopole. Both models are adequate to represent the vapour-liquid equilibrium, suggesting that the octopole makes an insignificant contribution to the properties of the bulk phase. Both models show that adsorbed CCl4 molecules are delocalized on a graphite surface because of the strong intermolecular interactions. It is found that the LJ sites on the chlorine atoms, not the octopole, play the most important role in matching the experimental isotherm and isosteric heat data with simulation. The heat is constant, across the first-order transition of the first adsorbate layer. The simulation results show that both the magnitude of the density jump, and the isosteric heat across the first-order transition, decrease as the temperature increases. This is in qualitative agreement with the 1972 experimental data of Avgul and Kiselev, but these experimental data exhibit an unusually strong decrease in the isosteric heat, and the coexistence region between the two phases displays an unusual asymmetrical shape. Detailed analysis of our simulation results, together with the calculated isosteric heat from the experimental isotherms of Machin and Ross, show that there may be errors associated with the heat data of Avgul and Kiselev at high temperatures.

Role of ultrafast dissociation in the fragmentation of chlorinated methanes.

Photon-induced fragmentation of a full set of chlorinated methanes (CH3Cl, CH2Cl2, CHCl3, CCl4) has been investigated both experimentally and computationally. Using synchrotron radiation and electron-ion coincidence measurements, the dissociation processes were studied after chlorine 2p electron excitation. Experimental evidence for CH3Cl and CH2Cl2 contains unique features suggesting that fast dissociation processes take place. By contrast, CHCl3 and CCl4 molecules do not contain the same features, hinting that they experience alternative mechanisms for dissociation and charge migration. Computational work indicates differing rates of charge movement after the core-excitation, which can be used to explain the differences observed experimentally.

A novel hexanuclear Zn6 metallacycle as a luminescent sensor for the Fe3+ ion and CCl4 molecule

A novel Zn6 metallamacrocycle based on a multidentate terpyridyl carboxylic acid ligand, namely [ZnL(HCOO)]6 (1), (HL = 4′-(4-carboxyphenyl)-2,2′:6′,2″-terpyridine), has been synthesized by the solvothermal method. Compound 1 was structurally characterized by elemental analysis, FT-IR, powder X-ray diffraction, thermogravimetric analysis and single-crystal X-ray diffraction. Compound 1 displays a hexanuclear Zn metallacycle structure, which extends into a honeycomb structure via π⋯π interactions. Compound 1 exhibits high selective sensing for the Fe3+ ion with great quenching efficiency and a low sensitive detection limit of 5.36 × 10−8 M. In addition, compound 1 is also a selective sensing material for the CCl4 molecule with a detection limit of 8.87 × 10−5 M. Furthermore, the luminescent sensing mechanisms for the Fe3+ ion and CCl4 molecule have been explored.

Free-radical reaction synthesis of carbon using nitrogenous organic molecules and CCl4

Carbon could be synthesized by the reaction between CCl4 and nitrogenous organic molecules (DMF, DMAC, HMTA, DETA, DEA, EN, and NMP).

Supramolecular complexes [M{NH(CH2)4O}{S2CN(C2H5)2 2] ∙ CCl4 (M = Zn or 63Cu(II)): Synthesis, structures, spectral and thermal properties

Solvated adducts of diethyldithiocarbamate complexes of zinc and copper(II) of the formula [M{NH(CH2)4O}{S2CN(C2H5)22] ∙ CCl4 (M = Zn (I) and 63Cu (II)) were obtained. 13C MAS NMR experiments revealed magnetic nonequivalence in the dithiocarbamate moieties of the adduct isomers, the morpholine heterocycles, and the outer-sphere solvate molecules. The rhombic anisotropy of the EPR parameters of magnetically diluted isotope-substituted complex II is due to the copper polyhedron geometry, which is intermediate between a tetragonal pyramid and a trigonal bipyramid, with the ground state of the unpaired electron resulting from the mixing \(3{d_{{x^2} - {y^{2 - }}}}\) of and \(3{d_{{z^{2 - }}}}\) of copper(II). According to X-ray diffraction data, complex I is a supramolecular complex combining structurally nonequivalent adduct molecules (A and B) and “guest” molecules (CCl4). In addition, the crystal lattice has an array of channels occupied by outersphere solvate CCl4 molecules (a structural type of lattice clathrates). An STA study of the thermal properties revealed three main thermolysis steps: desorption of the solvate CCl4 molecules, elimination of coordinated morpholine molecules, and thermolysis of the dithiocarbamate moiety of the adduct.

Synthesis of metal-carbon nanoparticles in pulsed UV-photolysis of Fe(CO)5-CCl4 mixtures at room temperature

Synthesis of iron-carbon nanoparticles in joint photolysis of iron pentacarbonyl (Fe(CO)5) and carbon tetrachloride (CCl4) has been studied. When mixtures containing iron pentacarbonyl and CCl4 are exposed to UV light, Fe(CO)5 molecules decompose to yield an atomic vapor of iron with well-known and easily controlled parameters, whereas CCl4 molecules decompose to give CCl3 radicals. A pulsed Nd:YAG laser (fourth harmonic, 266 nm) served as a source of light. The growth process of nanoparticles in condensation of supersaturated vapors was monitored by the laser extinction method; nanoparticle samples were examined with an atomic-force microscope. It was found that the concentration of the CCl4 additive affects the manner in which the optical properties of nanoparticles synthesized in a binary mixture change relative to the properties of nanoparticles synthesized in photolysis of pure Fe(CO)5, which indicates that a carbon shell grows on the surface of iron nanoparticles.

My Research History on the Chemical Standpoint-From Molecular Structure to Surface Science.

The structure of molecules using gas electron diffraction (GED) was my graduate study. However, I was making a new apparatus for precise measurements by GED and formulated a scheme for the least-squares analysis for a smooth continuous curve of scattering intensity. My research was completely shifted to the solid surface after moving to Gakushuin University, where I briefly studied the liquid structure of CCl4 molecules, and I then moved to the Institute for Solid State Physics, the University of Tokyo. My studies of surface science were focused on the electronic properties and related phenomena, and various experimental methods were developed. The plasmon dispersions elucidated the initial oxidation of aluminum and one-dimensional metal on Si(001)2 × 1-K. Irreversible phase transition was discovered on MgO(001) using the LEED Kikuchi pattern. The electronic structure of the dislocation was observed on MgO(001) by the electron time-of-flight method. The phase transition on Si(001) and the rotational epitaxy in a K monoatomic layer on Cu(001) were found. Next, I changed to studies of the dynamical phenomena on the surface, where very low energy reactive ion scattering on metal surfaces and laser-induced desorption caused by electronic transition of NO and CO molecules from metal surfaces were observed, and the hydrogen atom location at the surface and interface was measured with a high depth resolution using a resonance nuclear reaction of (1) H + (15) N(2+) at 6.385 MeV. Finally, I moved to the University of Electro-Communications and studied thin single-crystal oxide layers on transition metals, in which the band-gap narrowing was found, and then a Pt monoatomic layer was prepared on the α-Al(2)O(3) film.

Laser-assisted electron diffraction for femtosecond molecular imaging

We report the observation of laser-assisted electron diffraction (LAED) through the collision of 1 keV electrons with gas-phase CCl4 molecules in a femtosecond near-infrared laser field. In the angular distribution of the scattered electrons with the energy shifts of ±ℏω, we observed clear diffraction patterns which reflect the geometrical structure of the molecules at the moment of laser irradiation. Our results demonstrate that ultrafast nuclear dynamics of molecules can be probed by LAED with the high temporal (<10 fs) and spatial (∼0.01 Å) resolutions.

Dissociation of chloromethanes upon resonant σ* excitation studied by x-ray scattering

The dissociation process following the Cl K-shell excitation to σ* resonances is studied by high resolution spectroscopy of resonant elastic and inelastic x-ray scattering on CH3Cl, CH2Cl2, CHCl3, and CCl4 molecules. Calculations employing the transition potential and Delta-Kohn-Sham DFT approach are in good agreement with the measured total fluorescence yield and show the presence of a second quasidegenerate group of states with σ* character above the lowest σ* unoccupied molecular orbital for molecules with more than one Cl atom. A bandwidth narrowing and a nonlinear dispersion behavior is extracted from the Kα spectral maps for both σ* resonances. The fitted data indicate that the widths of the Franck-Condon distributions for the first and second σ* resonances are comparable for all the molecules under study. In addition, an asymmetric broadening of the emission peaks is observed for resonant elastic x-ray scattering with zero detuning on both σ* resonances. This is attributed to the fast dissociation, transferring about 0.15 of the scattering probability into higher vibrational modes.