Hydrogen Chloride Molecule Research Articles

Structure of (DMF)m(HCl)n complexes (m= 2, n = 3–4)

(DMF)2(HCl)3 and (DMF)2(HCl)4 heterocomplexes were studied for the first time in terms of the B3LYP/6-31++G(d, p) density functional calculation. The resulting data about their structure, stability, strength of intermolecular bonds, and degree of proton transfer in O...H...Cl bridges are compared with the results of a similar calculation fulfilled for (DMF)m(HCl)n clusters (m, n = 1–2) and with the experimental data on the structure and properties of acid-base complexes in DMF solutions of HCl. An extremely stable symmetrical cycle of four molecules — (DMF)2(HCl)2 — is assumed to be a structure-forming element of solution in the DMF-HCl system in the range of concentrations achievable under normal conditions. When [HCl]0 > [DMF]0, the “excess” hydrogen chloride molecules add to the chlorine atoms of this cycle, forming heterocomplexes with a branched structure. Addition of more HCl molecules to the (DMF)2(HCl)2 cycle appreciably increases the degree of proton transfer from acid to base molecule.

Field theoretic approach to dynamical orbital localization inab initiomolecular dynamics

Techniques from gauge-field theory are employed to derive an alternative formulation of the Car-Parrinello ab initio molecular-dynamics method that allows maximally localized Wannier orbitals to be generated dynamically as the calculation proceeds. In particular, the Car-Parrinello Lagrangian is mapped onto an $\mathrm{SU}(n)$ non-Abelian gauge-field theory and the fictitious kinetic energy in the Car-Parrinello Lagrangian is modified to yield a fully gauge-invariant form. The Dirac gauge-fixing method is then employed to derive a set of equations of motion that automatically maintain orbital locality by restricting the orbitals to remain in the ``Wannier gauge.'' An approximate algorithm for integrating the equations of motion that is stable and maintains orbital locality is then developed based on the exact equations of motion. It is shown in a realistic application (64 water molecules plus one hydrogen-chloride molecule in a periodic box) that orbital locality can be maintained with only a modest increase in CPU time. The ability to keep orbitals localized in an ab initio molecular-dynamics calculation is a crucial ingredient in the development of emerging linear scaling approaches.

Fumed silica synthesis. Influence of hydrogen chloride on the fumed silica particle formation process

AbstractInteraction of silicon dioxide molecule up to the small silica protoparticle and primary particle formation, and influence of hydrogen chloride (HCl), water (H2O) and inert molecules (nitrogen N2) “under flame condition” and “after cooling” on structure and properties of fumed silica were investigated by quantum‐chemical simulations. An attempt to give definition of surface concept on atomic level was made.

Studies on Unimolecular Metastable Decomposition of Several Organic Compounds

The unimolecular metastable decomposition mechanism of several organic compounds, which have small molecular weights, was investigated in this study by means of mass-analyzed ion kinetic energy (MIKE) spectrometry, D-labeling technique and molecular orbital (MO) calculations. Accurate mass determination is also described by using a multiple sprayers Nano-ESI arrangement on a double-focusing magnetic sector instrument in this thesis. For example, ‘Unimolecuar HCl Loss from the Molecular Ions of Chlorophenols, a “Ring-walk” Mechanism for a Chlorine Atom’ is described in this abstract. The loss of hydrogen chloride (HCl) is one of the main fragmentation processes in the molecular of o, m-, and p-chlorophenols in the metastable time window. By investigation of D-labeled compounds, it could be established that the eliminated HCl molecule contains only the hydroxyl hydrogen atom, not other benzene ring hydrogen atoms. This process is rationalized by the so-called “ring-walk” mechanism for a chlorine atom.

Discrete stages in the solvation and ionization of hydrogen chloride adsorbed on ice particles.

Ionization and dissociation reactions play a fundamental role in aqueous chemistry. A basic and well-understood example is the reaction between hydrogen chloride (HCl) and water to form chloride ions (Cl(-)) and hydrated protons (H(3)O(+) or H(5)O(2)(+)). This acid ionization process also occurs in small water clusters and on ice surfaces, and recent attention has focused on the mechanism of this reaction in confined-water media and the extent of solvation needed for it to proceed. In fact, the transformation of HCl adsorbed on ice surfaces from a predominantly molecular form to ionic species during heating from 50 to 140 K has been observed. But the molecular details of this process remain poorly understood. Here we report infrared transmission spectroscopic signatures of distinct stages in the solvation and ionization of HCl adsorbed on ice nanoparticles kept at progressively higher temperatures. By using Monte Carlo and ab initio simulations to interpret the spectra, we are able to identify slightly stretched HCl molecules, strongly stretched molecules on the verge of ionization, contact ion pairs comprising H(3)O(+) and Cl(-), and an ionic surface phase rich in Zundel ions, H(5)O(2)(+).

Theoretical investigation on reactivity of singlet radical phosphinidene: reaction mechanism of its reacting with polar hydrogen chloride molecule

We have obtained two initial complexes (linear HPHCl and HPClH), and studied the reaction mechanism of singlet radical phosphinidene with polar hydrogen chloride molecule by ab initio molecular orbital theory at HF/6-31G(d), MP2(fc)/6-311+G(d,p) and G2 levels. Moreover, we have also calculated the thermodynamic and kinetic functions from 100 to 1100K in steps of 200K making use of the statistical thermodynamics and Eyring transition state theory with Wigner correction. It is concluded that there are two parallel reaction paths: Reaction A, an addition reaction which has the transition state (TS) formed by three-membered ring, has thermodynamic favor but does not have kinetic favor at low temperatures. However, it has both thermodynamic favor and kinetic favor at high temperatures comparing with Reaction B, a dehydrogenation reaction which has the TS formed by four-membered ring.

Theoretical study of the hydrogen chloride trihydrate

AbstractStructural, energetic, and spectroscopic properties of the hydrogen chloride trihydrate (H2O)3HCl have been calculated by ab initio and density functional methods. The stationary points on the potential energy surface and the harmonic frequencies were obtained with the density functional theory, the second‐order Møller–Plesset theory, and the self‐consistent reaction field theory, while the corresponding interaction energies and binding energies were computed using the coupled‐cluster method restricted to single, double, and noniterative triple excitations. The origins of the bonding have been characterized by symmetry‐adapted perturbation theory of pair and three‐body interactions. The global minimum on the potential energy surface of the cluster corresponds to a cyclic structure with the water and hydrogen chloride molecules connected by hydrogen bonds. Another minimum, corresponding to an ionic form of the trihydrate, (H2O)2H3O+Cl−, has a binding energy only ≈2 kcal/mol higher than the global minimum, but it is separated by a large barrier. The pathway connecting the two minima has been found, and the structure of the corresponding transition state has been determined. The geometry of the ionic minimum agrees well with the crystal structure of the hydrogen chloride trihydrate from single‐crystal X‐ray diffraction studies. Also, the computed harmonic frequencies and their theoretical assignment are in agreement with the experimental data recorded in the gas phase in argon matrices and in the crystalline phase. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002

Electric dipole moment function of H 35Cl

The radial Schrödinger wave equation was solved numerically using an anharmonic potential function with 11 parameters to generate wavefunctions and vibration–rotation energy levels of the hydrogen chloride molecule H 35Cl. Measured line strengths available in the literature cover transitions up to v=7. Using the measured values of the line strengths along with the computed wavefunctions, a set of 135 dipole moment matrix elements M 0 v′(m) were calculated. Finally, the dipole moment coefficients, M 0, M 1,…, M 7, were evaluated from the matrix elements.

Electron-impact ionization of hydrogen chloride

Relative partial ionization cross sections for the formation of Cl+, Cl2+ and H+ from the hydrogen chloride molecule have been determined, from simultaneously recorded mass and two-dimensional ion–ion coincidence spectra, as a function of the ionizing electron energy from 30 to 200 eV. Precursor specific cross sections have been derived which quantify the contribution to the yield of each fragment ion from each level of ionization and the kinetic energy released in the fragmentation reactions of multiply charged HCl has been used to obtain thermodynamic information on the doubly and triply charged states. Analysis shows that at 100 eV electron energy double ionization contributes 12% of the total ion yield and 3% at 50 eV. At 100 eV the decay of HCl2+ by the loss of an H atom to form Cl2+ is a result of approximately 41% of the double ionization events, comparable to the frequency of charge separating dissociation (52%). The formation of Cl2+ has a threshold of 46.8 ± 1.5 eV and is assigned to population of the c5Σ− dication state. The observed threshold for forming long-lived dications (HCl2+) is consistent with the population of the ground state of the dication, and higher vibrational levels of this state appear to contribute to the yield of H+ + Cl+ ion pairs. The formation of metastable HCl2+ contributes a maximum of 0.6% to the ion yield. Long-lived HCl3+ ions are not detected but dissociative triple ionization makes up approximately 0.7% of the ion yield at 200 eV. We estimate the lowest lying dissociative state of HCl3+ lies at 72 ± 2 eV above the ground state of the neutral molecule.

Characterization of organometallic coordinative cluster compounds of silver by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) was successfully applied to characterize the organosilver coordinative cluster compounds, silver phenylacetylide and three silver thiolates, namely, silver tertiary butylthiolate, silver 2,6-dimethylbenzenethiolate, and silver 2, 6-dichlorobenzenethiolate. Samples and dithranol matrix were finely dispersed in 1:1 tetrahydrofuran (THF)/chloroform (CHCl(3)) mixed solvent. In most cases the monomer units remained intact during ionization, and the oligomeric molecular ions were produced through silver cationization, with a general molecular ion formula [nM + Ag](+). This was further verified by the relative abundances of the isotopic peaks within the molecular ion clusters, which were in close agreement with those theoretically calculated for nM cationized with one silver ion. In the case of silver 2, 6-dichlorobenzenethiolate, in addition to the dominant [nM + Ag](+) peaks, weak peaks corresponding to the successive losses of hydrogen chloride molecules were observed. Copyright 2000 John Wiley & Sons, Ltd.

Prediction of phase equilibria for binary systems of hydrogen chloride with ethane, propane and n-dodecane

In many industrially important processes hydrogen chloride occurs as one of the major constituents. Due to its corrosive nature, hydrogen chloride is not an easy substance to handle in industrial or experimental facilities and, as a consequence, accurate basic data of its mixtures is scarce. In this study, we examine the ability of two theoretical approaches, PACT (perturbed anisotropic chain theory), and SAFT (statistical associating fluid theory), to predict the phase behaviour of three binary mixtures of hydrogen chloride with n-alkanes. In the PACT approach, the molecules are modelled with Lennard–Jones spherical segments with a contribution to describe the dipole of the hydrogen chloride molecule. The non-sphericity of the n-alkane molecules is accounted for via Prigogine's approximation for the external degrees of freedom. In the SAFT approach, the molecules are represented by chains of spherical repulsive segments with attractive short-range sites. Hydrogen chloride is represented by a single sphere, with two attractive sites to model the dipole of the molecule. Chain molecules, such as the n-alkanes, are modelled fusing together a number of spherical segments. No attractive sites are included as these molecules are non-polar. We treat the long-range dispersion forces via variable-range square-well potentials; with the SAFT-VR approach. We find that both approaches accurately reproduce the experimental phase behaviour of the three mixtures for wide ranges of temperature and pressure. In the case of the SAFT-VR approach, both the critical region and the low temperature region are well represented with one set of parameters. However, the PACT approach requires two different sets of parameters: one for the critical region and one for lower temperature regions.

Rotational spectrum and spectroscopic constants of [formula omitted] and [formula omitted

The rotational spectrum of the 36 Ar⋯ H 35 Cl isotopomer of the Van der Waals dimer between an argon atom and a hydrogen chloride molecule has been observed in natural abundance with a molecular beam, cavity Fourier transform microwave spectrometer. The derived spectroscopic constants are compared with those redetermined for 40 Ar⋯ H 35 Cl and 40 Ar⋯ H 37 Cl , which have been obtained from new measurements of all rotational transitions below 19 GHz and a new data analysis inclusive of chlorine spin–rotation and hydrogen-chlorine spin–spin effects.

Ion/molecule reactions of naphthalene and 1-chloronaphthalene radical cations

Reactions of the naphthalene radical cation, C 10H 8 ·+, and the 1-chloronaphthalene radical cation, C 10H 7Cl ·+, with a series of small organic molecules including amines, alcohols, ethers and simple carbonyl compounds have been studied by the selected ion flow tube (SIFT) technique. Observed reactions for the naphthalene cation include the associated adduct with hydrogen atom elimination from the reactant ion or neutral, association without elimination and charge transfer. Reaction products of the naphthalene cation were identified by running isotopomeric reactions with deuterated naphthalene. Reactions of the chloronaphthalene cation are association with hydrogen atom, chlorine atom or hydrogen chloride molecule elimination from the adducts, association without elimination and charge transfer. Reaction channels depend on the ionization energy of the reactant and vary in the above order with decreasing ionization energy of the neutral. C 10H 7Cl ·+ is generally more reactive than C 10H 8 ·+. Most of the reactions are very slow except for charge transfer reactions with trimethylamine and triethylamine. No proton transfer channel takes place for any of the primary reactions. A naphthyne containing ion adduct is formed in the reaction of C 10H 7Cl ·+ with some molecules due to HCl elimination from the primary adduct.

Degradation and stabilization of poly (vinyl chloride). V. Reaction mechanism of poly(vinyl chloride) degradation

The degradation of poly(vinyl chloride) is a complex chain dehydrochlorination that consists of an initiation process to generate an active intermediate and a series of chain reactions that generates additional active intermediates with progressively increased numbers of double bonds. Each intermediate partitions between an intermediate with one more double bond and a stable conjugated polyene with the same number of double bonds. At low and moderate temperatures the thermal degradation of PVC in an inert atmosphere is a succession of molecular concerted reactions. The initiation process is a 1,2-elimination through a four center transition state requiring a synperiplanar conformation. It can be catalyzed by a molecule of hydrogen chloride that makes possible 1,2-elimination through a transition state of six centers with much lower activation enthalpy but also with very low activation entropy. There are two main chain reactions: the first is a 1,4-elimination from allylic chlorine atoms and methylenes cis- to a double bond through a transition state of six centers; the second is a 1,3-rearrangement of hydrogen atoms catalyzed by hydrogen chloride. The chain reaction is interrupted when a relatively stable trans- double bond is formed and no hydrogen chloride is present to catalyze trans-cis- isomerization or 1,3-rearrangement. Macro carbocations formed by heterolysis of carbon-halogen bonds in the presence of strong Lewis acids react much faster than does the original PVC in concerted elimination by 1,2- syn- or 1,4- cis- mechanisms promoting a so-called ‘catastrophic’, very fast degradation. Macro radicals formed by thermal homolysis, irradiation or reaction with promoters can also promote very fast hydrogen chloride elimination due to a special mechanism consisting of a 1,2-rearrangement of a chlorine atom followed by a concerted 1,3-elimination through a five center transition state.

Quantum-chemical calculations of the mechanism of some reactions of the insertion of silylenes and dichlorosilylenes into a single bond

Carbenes and silylenes can participate in some insertion reactions both in singlet and in triplet electronic states. The reactivity of silylenes depends on the nature of their substituents. AM1 and PM3 semiempirical calculations were performed for the reactions of silylene and dichlorosilylene insertion into the H-Cl bond of the hydrogen chloride molecule and the C-O bond of the furane molecule. The data obtained was used to propose probable mechanisms of these reactions.

Synthesis and properties of thiazole halohydrazones. 2. Interaction of 2-?-chlorobenzylidenehydrazino-4-ethoxy-carbonylthiazole with nucleophiles

In the interaction of 2-α-clzlorobenzylidenehydrazino-4-ethoxycarbonylthiazole with nucleophiles, two competing reactions take place. 1) nucleophilic replacement of the chlorine atom to form the corresponding substitution product; 2) elimination of a hydrogen chloride molecule, concluding in cyclization of the intermediate nitrilimine to form 3 phenyl-5-ethoxycarbonylthiazolo(2, 3-c]-1, 2, 4-triazole. The direction taken by the interaction depends on the nature of the nucleophile and is determined primarily by the ratio of basicity and nucleophilicity of the agent.

NMR studies of the proton equilibrium in basic ambient-temperature chloroaluminate ionic liquids

In basic mixtures of the molten salt composed of aluminum chloride and 1 -ethyl-3-methylimidazolium chloride, proton, in the absence of oxides, is partitioned between hydrogen chloride and hydrogen dichloride ion. The equilibrium between these two species has been examined by 2H and 'H NMR spectroscopies. The magnitude of the hydrogen chloride/dichloride equilibrium constant demonstrates that the equilibrium strongly favors the formation of the hydrogen dichloride ion. The ratio of 2H and IH equilibrium constants at 90 OC gave an equilibrium isotope effect of 0.67 f 0.26, which indicates that deuterium accumulates in the hydrogen chloride molecule. An equilibrium isotope effect of 0.7 12 was calculated from hydrogen chloride and hydrogen dichloride vibrational frequencies. Analysis of the temperature dependence of the hydrogen chloride/dichloride equilibrium constant gave values for the enthalpy of reaction, MMN, and the entropy of reaction, LS, of -9.8 f 0.8 kJ mol-' and 4.8 f 2.5 J mol-' K-1, respectively. Comparison of the AH for the hydrogen chloride/dichloride equilibrium in the melts with values obtained for other solvents suggests that the melt interacts more strongly with chloride ion than with hydrogen dichloride ion.

Research on the thermal decomposition of the bioinorganic complex of europium and l-glutamine by Mössbauer spectroscopy

Mössbauer spectroscopy has been used to investigate the thermal decomposition of the bioinorganic complex of europium and l-glutamine. The Mössbauer parameters can demonstrate that the water molecules in the complex and the chlorine anion in the hydrogen chloride molecule, dissociated from the complex below 200°C, are not linked directly to the europium atom. The thermal decomposition process of the complex is discussed and a possible coordination model for the europium l-glutamine complex is also proposed on the basis of the thermogravimetric and derivative thermogravimetric curves, and from some evidence obtained from the Mössbauer effects of some decomposition products of the complex.

Heterocyclization of ?,?-dichloro ketones as a method for the synthesis of furan derivatives

Dichloro ketones obtained from acyl chlorides and allyl or β-methylallyl chloride undergo spontaneous cyclization to give 2-alkyl- and 2,4-dialkylfurans when they are heated; the intermediates in the case of 2,3-dichloropropene split out a molecule of hydrogen chloride to give 3,4-dichloro-2-butenones.

Site of Chlorine Interaction With a Cation-Exchange Resin (Chelex-100)

X-Ray photoelectron spectroscopy, 13C and 1H solution-state n.m.r., and 13C solid-state n.m.r. were used in chlorination studies on compounds, which act as models for the exchange group and the styrene divinylbenzene copolymer backbone of Chelex-100, to determine the site and mechanism of chlorine attack. Results indicate that the resin cleaves upon chlorination, and a cleavage mechanism, involving initial attack by chlorine on the exchange group imine nitrogen electron lone pairs, is proposed. The N-halo quaternary species formed loses a molecule of hydrogen chloride to give a Schiff base, which undergoes hydrolysis to an aldehyde and an ammonium salt.