Vibrational energy disposal in reactions of fluorine atoms with hydrides of groups III,IV and V

The HF infrared chemiluminescence from the reactions of F atoms with B₂H₆, CH₄, CH₃F, CH₂F₂, CH₂Cl₂, CH₃ONO. CH₃NO₂, NH₃ (and ND₃). PH₃ and HNCO has been observed from a 300 K flowing-afterglow reactor. Experiments were done for a range of CH₄ and F atom concentrations to identify conditions which were free of vibrational relaxation and secondary reactions, and these conditions were used to assign initial HF(v) vibrational distributions for each reaction. The emission intensity from each reaction also was compared to that from CH₄ in order to obtain the relative HF formation rate constants at 300 K. Since the absolute rate constant for F + CH₄ is well established, the combination of all of these data provides absolute rate constants for HF(v) formation at 300 K. The ND₃ reaction was studied to obtain information on more vibrational levels in order to better estimate the HF(v = 0) and DF(v = 0) components of the ammonia distributions. With NH₃ and ND₃ there is no significant isotope effect on the energy disposal. Except for NHCO, for which an addition-elimination channel is possible, the HF(v) distributions are inverted and <f_v > = 0.60. Differences between the HF(v) distributions reported here and some other reports in the literature are noted: the present data are discussed as representative of direct H atom abstraction for 300 K Boltzmann conditions. The HCl infrared chemiluminescence from the F + CHCl₂ secondary reaction also was observed; the HCl(v) distribution was v₁: v₂: v₃: v₄: v₅ - 0.47: 0.23: 0.18: 0.08: 0.04.     

Infrared chemiluminescence in the reactions of 0.45 eV hydrogen atoms with Cl2, SCl2 and PCl3

Infrared chemiluminescence from HCl has been observed in “arrested relaxation” experiments to yield vibrational and rotational distributions from the reactions $\text{H}$+Cl₂, SCl₂ and PCl₃, where $\text{H}$ denotes hydrogen atoms with translational energy of 0.45 eV. The following relative populations were determined: N_v-1: N_v-2: N_v-3: N_v-4: N_v-5: N_v-6 = 0.89:1.00:0.84:0.47:0.26:0.11 for $\text{H}$+Cl₂: N_v-1: N_v-2: N_v-3: N_v-4: N_v-5: N_v-6 = 0.80:1.00:0.72:0.48:0.24:0.10 for $\text{H}$+SCl₂: N_v-1: N_v-2: N_v-3: N_v-4: N_v-5 = 0.79:1.00:0.88:0.36:0.14 for H+PCl₃. In all three reaction systems the chemiluminescence was attributed to the primary chlorine abstraction. Comparison with the results of the thermal processes (0.04 eV hydrogen atoms) led to the following conclusions: for H+Cl₂ the excess of translational energy is transformed into translational product energy and rotational energy of the molecule HCl; for H+SCl₂ the excess of translational energy is transformed mainly into translational energy of the products and perhaps internal energy of SCl; for H+PCl₃ the excess of translational energy allows the observation of the primary abstraction reaction, which could in earlier experiments at 300 K not be separated from secondary chemiluminescent processes. Bimodal rotational distributions were confirmed for several vibrational states of HCl formed in the systems $\text{H}$+Cl₂, and $\text{H}$+SCl₂. Bimodal rotational distributions were also detected in the chemiluminescent reaction H(0.04 eV)+CH₃SCl → HCl(v ? 5)+CH₃S.     

Comparisons of energy disposal by the reactions of H atoms with Cl2, SCl2, S2Cl2 and SO2Cl2 from observation of HC1 infrared chemiluminescence

Arrested relaxation infrared chemiluminescence studies of the H + Cl₂, SCl₂, S₂Cl₂, SOCl₂ and SO₂-Cl₂ reactions have been made. The mean fraction of vibrational (stational) energy released to HCl is 0.40 (0.10); 0.40 (0.13); 0.38 (? 0.02); 0.33 (?0.02) and 0.36 (?0.02) for the series. Only the H + SCl₂ reaction shows a two component initial rotational distribution. The larger (f_V) and (f_R) from H + SCl₂, relative to the other polyatomic reagents, is consistent with the observation that this is the only reaction that shows forward scattering. The room temperature rate constants also were measured, relative to H + Cl₂, and were found to decline in the series from 0.68 for SCl₂ to 0.02 for SO₂Cl₂. All of these data support the suggestion (first made by Heydtmann and Polanyi) that the unusual rotational energy disposal pattern from H + SCl₂ is a consequence of migration of H from the initially encountered C1 to the second C1, which then forms the HCI product; this pathway augments the direct reactive pathway, which gives HCI in lower J states.     

Investigation on the mechanism and applications of the reaction Cl2+2HBr=2HCl+Br2

The mechanism of reaction Cl₂+2HBr=2HCl+Br₂ has been carefully investigated with density functional theory (DFT) at B3LYP/6-311G^** level. A series of three-centred and four-centred transition states have been obtained. The activation energy (138.96 and 147.24 kJ/mol, respectively) of two bimolecular elementary reactions Cl₂+HBr→HCl+BrCl and BrCl+HBr→HCl+Br₂ is smaller than the dissociation energy of Cl₂, HBr and BrCl, indicating that it is favorable for the title reaction occurring in the bimolecular form. The reaction has been applied to the chemical engineering process of recycling Br₂ from HBr. Gaseous Cl₂ directly reacts with HBr gas, which produces gaseous mixtures containing Br₂, and liquid Br₂ and HCl are obtained by cooling the mixtures and further separated by absorption with CCl₄. The recovery percentage of Br₂ is more than 96%, and the Cl₂ remaining in liquid Br₂ is less than 3.0%. The paper provides a good example of solving the difficult problem in chemical engineering with basic theory.     

Zur Kenntnis des Aluminiumchlorids. Die Umsetzung von AlCl3 mit PCl5 und Methylamin

Aluminium trichloride forms the adducts AlCl₃ · NH₂CH₃, AlCl₃ · 2NH₂CH₃, AlCl₃ · 4NH₂CH₃; AlCl₃ · NH₃CH₃Cl, AlCl₃ · 2NH₃CH₃Cl. The interaction between AlCl₃, PCl₅ and NH₃CH₃Cl in the molar ratio 1:3:2 proceeds according to the reaction equation in “Inhaltsübersicht”. On applying other stoichiometric amounts, [Cl₂(NHCH₃)P? N(CH₃)? AlCl₃] · HCl and [Cl₃P? N(CH₃)? AlCl₃] · HCl are obtained; the latter reacts as [Cl₃P? NHCH₃][AlCl₄]. At the molar ratio AlCl₃:PCl₅:NH₃CH₃Cl = 1:2:4 a compound is formed being presumably the six-membered heterocycle formulated in “Inhaltsübersicht”. With [Cl₃P?N? PCl₃] and aluminium chloride [Cl₃P?N? PCl₃][AlCl₄] is formed.     

An electrical conductivity (EC) study of the thermal dissociation of [Co(NH3)6]X3 and [Co(en)3]X3 complexes

The thermal dissociation of the [Co(NH₃)₆]X₃ (X = Cl^?, Br^?, I^?, and NO^?₃), [Co(en)₃]X₃ (X = Cl^?, Br^?, I^?, NO^?₃, HSO^?₄ and $\text{1}\text{2}$ C₂O^2?₄), cis- [Co(en)₂Cl₂]Cl, and trans-[Co(en)₂ClBr]NO₃ complexes was investigated by an electrical conductivity (EC) technique. During the thermal dissociation reactions, liquid or semi-liquid phases are formed which cause large increases in the EC of the compound. The effect of concentration of the complex in a matrix medium as well as the composition of the matrix material on the EC curves were also determined.     

Investigation on the mechanism and applications of the reaction Cl2+2HBr=2HCl+Br2

The mechanism of reaction Cl₂+2HBr=2HCl+Br₂ has been carefully investigated with density functional theory (DFT) at B3LYP/6-311G^** level. A series of three-centred and four-centred transition states have been obtained. The activation energy (138.96 and 147.24 kJ/mol, respectively) of two bimolecular elementary reactions Cl₂+HBr→HCl+BrCl and BrCl+HBr→HCl+Br₂ is smaller than the dissociation energy of Cl₂, HBr and BrCl, indicating that it is favorable for the title reaction occurring in the bimolecular form. The reaction has been applied to the chemical engineering process of recycling Br₂ from HBr. Gaseous Cl₂ directly reacts with HBr gas, which produces gaseous mixtures containing Br₂, and liquid Br₂ and HCl are obtained by cooling the mixtures and further separated by absorption with CCl₄. The recovery percentage of Br₂ is more than 96%, and the Cl₂ remaining in liquid Br₂ is less than 3.0%. The paper provides a good example of solving the difficult problem in chemical engineering with basic theory.     

Hydrogen abstraction by fluorine atoms: F + HX and F + DX (X = I,Br, Cl)

Absolute reaction rates for F + HX and F + DX (X = I, Br, Cl) have been obtained by monitoring the rise time of HF (DF) vibrational fluorescence following multiphoton dissociation of SF₆ in mixtures of HX (DX) and argon. The cross sections for reaction are, in units of 10^?16 cm², 4.37, 5.26, and 1.16 for HI, HBr, and HCl, respectively. The isotope effects k_HX/k_DX, are 1.29 ± 0.14, 1.29 ± 0.18, and 1.38 ± 0.29, respectively.     

Reactions of halogens with platinum(IV) triamine complexes [PtEnPyX3]X (X = Cl, Br)

Platinum(IV) complexes of the tetramine type [PtEnPy₂X₂]X₂ · H₂O (X = Cl, Br) have been found to lose a coordinated pyridine molecule at 125–135°C, thereby transforming into triamines [PtEnPyX₃]X. The complex [PtEnPyCl₃]NO₃ has been isolated. Dissolution of the product of [PtEnPy₂Cl₂]Cl₂ chlorination in HCl results in complete destruction of the five-membered chelate ring. The complex [Pt(NH₃)₂Py₂Cl₂](NO₃)₂ has been isolated. A number of compounds have been studied by X-ray diffraction: [PtEnPy₂Cl₂]Cl₂ · 2H₂O (I) (monoclinic, space group P2₁/c, a = 15.418(2) Å, b = 9.203(1) Å, c = 13.762(3) Å, β = 104.18(2)°, Z = 4, R _hkl = 0.25), [PtEnPyCl₃]NO₃ (II) (monoclinic, space group P2₁/c, a = 8.194(1) Å, b = 8.846(1) Å, c = 19.855(2) Å, β = 97.10(1)°, Z = 4, R _hkl = 0.048), and [Pt(NH₃)₂Py₂Cl₂](NO₃)₂ (III) (orthorhombic, space group Pbca, a = 12.316(2) Å, b = 13.250(3) Å, c = 21.868(4) Å, Z = 8, R _hkl = 0.027). The reaction of [PtEnPyBr₃]Br with bromine gives the polybromide [PtEnPyBr₃]Br · Br₂ · 0.5 H₂O. The chlorination of [PtEnPyCl₃]Cl gives the chloramine complex [Pt(NH₂-CH₂-NH(Cl)PyCl₃]Cl · H₂O.     

Gas-phase C-F bond cleavage in perfluorohexane using W-, Si-, P-, Br-, and I-containing ions: Comparisons with reactions at fluorocarbon surfaces

Gas-phase reactions of W-, Si-, P-, Br-, and I-containing ions with the target molecule perfluorohexane at low collision energies (<15 eV) parallel known ion/surface reactions of the same projectile ions at fluorinated self-assembled monolayer surfaces. Charge exchange, dissociative charge exchange, and fluorine atom abstraction are observed and the majority of the projectile ions also undergo reactive charge exchange to produce specific fluorocarbon fragment ions of the target molecule in distinctive relative abundances. Abstraction of up to five fluorine atoms is observed upon collision of W⁺ with gaseous perfluorohexane, while similar experiments with CI⁺, SiCl⁺, and PCl^+· show abstraction of one or two fluorine atoms. Other projectiles, including Si^+·, PCl ₂ ⁺ , Br⁺, CBr⁺, and I⁺, abstract only a single fluorine atom. These patterns of fluorine atom abstraction are similar to those observed in ion/surface collisions. Also paralleling the ion/surface reactions, halogen exchange (Cl-for-F) reactions occur between the Cl-containing projectile ions and perfluorohexane to produce C₆F₁₂Cl⁺, a product of chemical modification of the target. Collisions of PCl^+· and PCl ₂ ⁺ also result in production of C₆F ₁₂ ^+· , indicating that the corresponding surface modification reaction involving molecular defluorination should be sought. Implications for previously proposed mechanisms, new ion/surface reactions, and for the use of gas-phase studies to guide investigations of the ion/surface reactions are discussed.     

Integrated Hydrogeological,Hydrochemical, and Isotopic Assessment of Seawater Intrusion into Coastal Aquifers in Al-Qatif Area,Eastern Saudi Arabia

Seawater intrusion (SWI) is the main threat to fresh groundwater (GW) resources in coastal regions worldwide. Early identification and delineation of such threats can help decision-makers plan for suitable management measures to protect water resources for coastal communities. This study assesses seawater intrusion (SWI) and GW salinization of the shallow and deep coastal aquifers in the Al-Qatif area, in the eastern region of Saudi Arabia. Field hydrogeological and hydrochemical investigations coupled with laboratory-based hydrochemical and isotopic analyses (¹⁸O and ²H) were used in this integrated study. Hydrochemical facies diagrams, ionic ratio diagrams, and spatial distribution maps of GW physical and chemical parameters (EC, TDS, Cl⁻, Br⁻), and seawater fraction (f_sw) were generated to depict the lateral extent of SWI. Hydrochemical facies diagrams were mainly used for GW salinization source identification. The results show that the shallow GW is of brackish and saline types with EC, TDS, Cl⁻, Br⁻ concentration, and an increasing f_sw trend seaward, indicating more influence of SWI on shallow GW wells located close to the shoreline. On the contrary, deep GW shows low f_sw and EC, TDS, Cl⁻, and Br⁻, indicating less influence of SWI on GW chemistry. Moreover, the shallow GW is enriched in ¹⁸O and ²H isotopes compared with the deep GW, which reveals mixing with recent water. In conclusion, the reduction in GW abstraction in the central part of the study area raised the average GW level by three meters. Therefore, to protect the deep GW from SWI and salinity pollution, it is recommended to implement such management practices in the entire region. In addition, continuous monitoring of deep GW is recommended to provide decision-makers with sufficient data to plan for the protection of coastal freshwater resources.     

Bildung siliciumorganischer Verbindungen. 98. Umsetzung silylierter Phosphorylide mit PCl3

Formation of Organosilicon Compounds. 98. Reaction of Silylated Phosphorus Ylides with PCl₃ The reaction of Si-substituted phosphorus ylides as Me₂Si(CH₂? SiMe₂)₂C?PMe₃Br 1 , Cl₂Si(CH₂? SiCl₂)₂C?PMe₂Cl 2 , and (Cl₃Si)₂C?PMe₂Cl 3 with PCl₃ yields (Cl₂P)₂C?PMe₂Cl 5 by chlorinating cleavage of the Si-ylid-C bond. Besides 5 also (ClMe₂SiCH₂)₂SiMe₂, (Cl₃SiCH₂)₂SiCl₂, resp. SiCl₄ result from the reaction of 1, 2 and 3 with PCl₃. (Cl₂P)₂C?PMe₂Cl forms colourless crystals, mp. 84°C.     

Synthesis and structural characterization of metal complexes based on pyrazole/imidazolium chlorides

A series of imidzoalium salt, L · HCl, for the potentially bidentate pyrazole/N-heterocyclic carbene was synthesized. Reactions of a 2:1 mixture between L · HCl bearing bulky N-substitution and Ag₂O produced Ag(L)Cl, whereas a novel compound with unique stoichiometry AgL₂(AgCl)_0.5Cl was produced from L · HCl bearing N-methyl group under identical condition. Reactions of L · HCl with PdCl₂ produced zwitterionic Pd^IICl₃L · H. Selected structural determinations on L · HCl, Ag(L)Cl, AgL₂(AgCl)_0.5Cl, and Pd^IICl₃L · H revealed intriguing crystal chemistry in which the less-stable gauche rotamers were obtained exclusively. A preliminary application of the zwitterionic complexes, Pd^IICl₃L · H, in Heck coupling reaction of aryl bromide with n-butyl acrylate shows effective activity.     

Komplexbildung mit 1,2-bis (o-Aminobenzylidenamino)-ethan als neutralem Liganden

Compounds [Co(H₂ L]X ₂(X=Cl, Br, I, NO₃, ClO₄), [Co(H₂ L–Br₂)]Br₂, [Co(H₂ L–Br₂)·py ₂]Br₂ and [Co(H₂ L)Cl]Cl₂ were isolated. They were investigated by means of thermoanalysis, IR and VIS spectroscopy, magnetochemistry and molar conductivity.

     

Solids containing methylhalophosphonium cations [(CH3)n PX+4−n] (n = 1–3 XCl,Br): an investigation using magic-angle spinning NMR spectroscopy

A selection of complexes containing [(CH₃)nPX⁺_4−n] cations (XCl, Br) have been investigated by magic-angle spinning (MAS) ³¹P and ¹¹B NMR spectroscopy. Qualitative information about ionic motion in these systems is derived from the observed linewidths, which are dependent upon the nature of the anions present in the lattices. Isomers of [(CH₃)PCl⁺₃Cl⁻] and [(CH₃)₂PCl⁺₂Cl⁻] are detected, confirming previous Raman spectroscopic observations. The mixed-halogen cations [(CH₃)PCl₂Br⁺], [(CH₃)PClBr⁺₂] and [(CH₃)₂PClBr⁺] are also observed, complexed with both single-halide and polyatomic anions. Differences in NMR linewidths are again noted. These results are compared with Raman studies on the same complexes and contrasted with a similar investigation of the [PCl_nBr⁺_4−n] (O⩽n⩽4) system.     

Über Trichlorphosphazo-Verbindungen aus Nitrilen. III. Die Reaktion zwischen Acrylnitril und PCl3

On Trichlorophosphazo Compounds from Nitriles. III. The Reaction between Acrylonitrile and PCl₃. The reaction of PCl₃ with acrylonitrile at higher temperatures gives CH₂Cl? CCl₂? CCl₂? N? PCl₃ ( II ). On pyrolysis of (II), CH₂Cl? CCl₂? CN (IV) is form- ed. Treatment of (II) with SO, results in CHzCL? CCl₂? CCl?N-P(0)Cl₂ ( III ). At lower temperatures and/or in the presence of PCl₃, acrylonitrile reacts with PCl₃ to give the cis/ trans isomers VIa and VIb .     

Complexes of N′-(4-phenyl thiazole-2-yl) thiourea with some first row transition metals

Metal complexes of N′-(4-phenyl thiazole-2-yl) thiourea (L) possessing the stoichiometry, [MLX₂] (M = Cu²⁺; X = Cl⁻, Br⁻, NO₃⁻ and ClO₄⁻), (M = Ni²⁺; X = Cl⁻), (M = Co²⁺; X = Cl⁻, NO₃⁻) have been isolated and studied. Tentative geometry of the complexes has been deduced by elemental analyses, magnetic and spectroscopic techniques. Fungicidal screening of the complexes has been made against Helminthosporium oryzae, Fusarium oxysporium and Aspergillus niger.     

The Reaction X + Cl2→XCl + Cl (X = Mu,H, D). II. Comparison of experimental data with theoretical results derived from a new potential energy surface

We consider experimental implications for the Mu + Cl₂, H + Cl₂, and D + Cl₂ reactions of the extended London—Eyring—Polanyi—Sato (LEPS) potential energy surface derived from experimental data in paper I. In the present calculations, it is necessary to make additional implicit and explicit assumptions concerning the three-dimensional (3D) nature of the potential surface, since the inversion procedure of paper I yields information only on the collinear (1D) part of the surface. We have performed accurate 1D quantum calculations of reaction probabilities, which are then transformed into 3D by an information theoretic 1D → 3D transformation incorporating a constraint to allow for angular momentum transfer effects in light+heavy—heavy atom reactions. This procedure implicitly accounts for the 3D nature of the potential surface. The calculated vibrational and vibrotational product distributions are in good agreement with those determined in thermal chemiluminescence experiments. The Sato parameters for the 1D surface also define a full 3D surface. This is used as an approximation to the true surface, and its properties are explored in 3D quasiclassical trajectory calculations. Comparison is made for the H and D reactions with available chemiluminescence, molecular beam and kinetic experimental data for differential and total reaction cross sections, energy disposal, rate coefficients and Arrhenius parameters. Some kinetic isotope effects in the Mu, H, and D reactions are discussed using vibrationally adiabatic theory. Comparison is also made with results from other calculations in the literature for the H + Cl₂ and D + Cl₂ reactions.     

Die Umwandlung [W6X8]X4 [W6X12]X6 (X = Cl,Br)

Transformation of [W₆X₈]X₄ + 3 X₂ = [W₆X₁₂]X₆ (X = Cl, Br) The transformation of [W₆X₈]X₄ + 3 X₂ = [W₆X₁₂]X₆ (X = Cl, Br) has been investigated by changing the relation Cl₂/Br₂ and the temperature. In this way the compounds [W₆Br_12?nCl_n]Cl_6?mBr_m are isolated. All of the products are isotypic with W₆Cl₁₈ and W₆Br₁₈. Most often n equals 6, however compounds with other relations of Cl/Br are also observed (e. g. n = 4.8) The 6 ligands standing outside of the brackets are replaced by Cl or Br. The substitution of [W₆Br₆Cl₆]Cl₆ by means of bromine leads to the cluster [W₆Br₁₂]X₆. The backward transformation of the cluster compound [W₆Br₁₂]Br₆ happens by decomposition on the thermobalance, e. g. according to Gl. (1) (See Inhaltsübersicht). By analogy [W₆Br₁₂]Cl₆ is decomposed to [W₆Br₈]Cl₂Br₂, which by treatment with conc. HCl is transformed into [W₆Br₈]Cl₄ · 2 H₂O.