Application of multiconfigurational many-body perturbation theory to the calculation of ionization potentials,electron affinities and excitation energ

Multiconfigurational many-body perturbation theory is applied to the problem of calculating ionization potentials, electron affinities, and excitation energies. H₂O, C₂H₄, and H₂ are studied, with correlation corrections through third order and inclusive of certain higher-order terms. Results are compared with those by other many-body theoretical methods.     

Laser-pulse photocurrent transient measurements at oxygen evolving n-PtS2

Laser-pulse transient measurements have been performed at single crystalline n-PtS₂ electrodes with the aim of understanding light-induced hydroxide, oxide and oxygen formation. Different detected time constants permit the identification of distinct reaction products. They form surface states which function both as centers for recombination and charge accumulation in the interface. The rate constants determined are influenced by the RC-constant of the measuring circuit and can be interpreted only qualitatively. In the presence of recombination processes time constants faster than R_LC_SC are found. Evidence is given that the reaction step leading to oxygen evolution is dependent on the building-up of an electric field in the Helmholtz layer. This result may be of importance for the development of materials for the photoelectrolysis of water.     

Cluster configuration method: application to the spectra of π-electron systems

A simplified method to calculate the excitation spectra of π-electron systems is proposed. The method is based on the assumption that a “cluster” approximation can be applied to excited states. It is demonstrated that, for the low-lying triplet and optically allowed states of butadiene, hexatriene and benzene, the method yields good agreement with complete CI calculations in the Pariser–Pan–Pople approximation.     

Molecular structure of carbonyl fluoride as studied by gas electron diffraction and microwave data

The molecular structure of carbonyl fluoride has been determined by electron diffraction. The results have been used in conjunction with the rotational constants reported by Carpenter in a combined structure analysis. The values so obtained are r_z (C=O) = 1.1717 ± 0.0013 Å, r_z (C-F) = 1.3157 ± 0.0005 Å, and ∠_zF-C-F = 107.71 ± 0.08°. These agree with the corresponding parameters estimated by Carpenter from the rotational constants alone. The effective constants, α₃, representing the cubic anharmonicity of bond stretching vibrations have been estimated.     

The extraction of niobium (V) and Tantalum (V) by Octylarsinic acid in chloroform

Dioctylarsinic acid (HDOAA) in chloroform solution extracts Nb(V) and Ta(V) efficiently from solutions containing oxalate and oxalic acid at hydrochloric acid concentrations greater than 1M.The extraction coefficients are 92.5 at 7M hydrochloric acid and 251 at 6M hydrochloric acid for niobium and tantalum, respectively. These metals can be extracted even more efficiently from sulfuric acid solutions. The results of the reagent- and pH-dependence studies suggested that a trimeric, monobasic oxoacid of niobium, associated with ten HDOAA molecules, is extracted. Tantalum appears to be present in the organic phase as (H₂DOAA)⁺ [Ta(C₂O₄)₃ (HDOAA_n] (n=l or 2).     

Determination of nickel in standard rocks and glasses by photon activation analysis with 30-MeV bremsstrahlung

The determination of nickel in various silicate rocks and glasses by photon activation analysis with a linear electron accelerator is described. Simultaneous irradiation of the sample and comparative standards produces the ⁵⁸Ni(γ, n)⁵⁷Ni reaction, and a post-irradiation chemical separation is used in conjunction with Ge(Li) γ-spectrometry. Nickel abundances for ten standard silicate rocks and two elementally doped glasses are presented and compared with the data previously published. The method is quite simple and gives good reproducible results for nickel down to sub-p.p.m. levels.     

Molecular structure of carbonyl bromide as studied by gas electron diffraction

The molecular structure of COBr₂ has been determined as follows by an analysis of electron diffraction intensity: r_g(CO) = 1.178 ± 0.009 Å, r_g(C-Br) = 1.923 ± 0.005 Å and θ°_α(Br-C-Br) = 112.3 ± 0.4°. The uncertainties represent estimated limits of error. The observed systematic trends in the bond lengths and bond angles in carbonyl and thiocarbonyl halides are discussed.     

Infrared-induced conformational isomerization of ethylene glycol in a low-temperature argon matrix

The paramagnetic BrO₂ molecule with lifetime τ > 10 s has been found amoung the products of the O + Br₂ reaction in a discharge flow system. Identification was made by the technique of molecular beam focusing in an inhomogeneous magnetic field with mass-spectrometric detection. Its symmetry appeared to be C₂, like the stable OClO molecule, as was determined by focusing in an inhomogeneous electric field. Approximate rate constants for the reactions O + BrO₂ (k₃ = (2.5–6)×10^?12 cm³/s) and Br + BrO₂ (k₇ = 5 × 10^?11 cm³/s) were obtained.     

Assignment of photoelectro bands for naphthalene and anthracene by penning ionization electron spectroscopy

The Ne¹(³P₂) Penning electron spectra and the Ne I photoelectron spectra were measured in the gas phase. The observed systematic differences in their relative intensities were interpreted in terms of the electron distributions of the relevant molecular orbitals and used for assignment of the deep π bands, π₁ (12.4 eV) for naphthalene, and π₂ (11.9 eV) and π₁ (12.8 eV) for anthracene.     

Energy and angular differential cross sections for K + NO2 charge transfer reactions

Doubly differential cross sections, in energy and angle, are reported for the electron transfer reaction between potassium and nitrogen dioxide in a crossed beam apparatus at relative collision energies between 2.7 and 30.8 eV. The formation of NO^?₂ in its ground ¹A₁ and excited ³B₁ state has been observed. Theoretical consideration of these processes indicates that bond bending during the collision has a stronger influence on ion-pair formation than bond stretching. At the lower collision energies most of the excess energy is converted into internal energy of NO^?₂.     

Effect of spin-orbit coupling in para-dihalogenobenzenes on the environment-induced frequency changes in their S1 ← S0 spectra

The consequences of spin-orbit coupling in p-dihalogenobenzenes for solvent-induced shifts or S₁ ← S₀ spectral transitions, and for changes of S₁-state vibrational frequencies compared with the S₀ state, are assigned to mixing low-energy triplet states into the singlet-state system.     

General theory of vibrational mode mixing and frequency shifts in resonance raman scattering

A general formalism is given for treating vibrational mode mixing, frequency shifts, and atomic equilibrium position shifts under electronic excitation in resonance Raman scattering. The theory is exact for first-order scattering at T = 0 K for all linear and quadratic electron-phonon coupling strengths. Numerical results illustrating mode mixing are presented.     

The conformation and vibrational spectra of trans-1,4-dihalocyclohexanes: Part II. trans-1,4-Chlorobromocyclohexane and trans-1,4-chloroiodocyclohexane

The IR spectra of trans-1,4-chlorobromo- and trans-1,4-chloroiodocyclohexane were recorded in the region 4000–30 cm^?1 as solutes in various solvents, as KI and polyethylene pellets and as solids under high pressure (1–50 kbar at ambient temperature). Additional spectra of the melts, amorphous and annealed crystalline solids at 90 K and dichroism of oriented polycrystalline films were obtained above 200 cm^?1. Raman spectra of the compounds were recorded in the amorphous and crystalline states at 90 K, and polarization measurements were made in CCl₄ CS₂ and C₆H₆ solution.The title compounds existed as an equilibrium mixture of ee and aa conformers in solution, in the melts and in the amorphous solids at 90 K. When heated to temperatures in the region 165–195 K the amorphous solids apparently crystallized into a metastable form containing the aa conformer, while above 200 K the solids were converted to a stable crystal containing the ee conformer. Under high pressure the concentration of the aa conformer increased and this form was almost exclusively present at ca. 50 kbar nominal pressure.The fundamental frequencies for both conformers were assigned in terms of C_smolecular symmetry. An extensive normal coordinate analysis on six trans-1,4-dihalocyclohexanes was carried out using the overlay technique.     

Synthesis of 2,3,4-trideoxy-4-c-(phenylphosphinyl)-dl-glycero-pentofuranose and its 1,5-diacetate

Synthesis of 2,3,4-trideoxy-4-C-(phenylphosphinyl)-dl-glycero-pentofuranose (11) starting from 2-furanmethanol was successful. The reaction of methyl 2,3-dideoxy-(1S)-dl-pentopyranosid-4-ulose 4-(p-toluenesulfonylhydrazone) with methyl phenylphosphonite gave methyl (4RS)-2,3,4-trideoxy-4-C-[(methoxy)phenylphosphinyl]-4-C-(p-toluenesulfonylhydrazino)-(1S)-dl-pentopyranoside (7), which on treatment with sodium borohydride afforded methyl 2,3,4-trideoxy-4-C-[(methoxy)phenylphosphinyl]-(1S)-dl-glycero-pentopyranoside (9). Treatment of compound 9 with SDMA followed by hydrolysis and treatment with acetic anhydride-pyridine afforded 1,5-diacetate 12 of compound 11.     

Reaction of organic sulfur compounds with superoxide anion—III : Oxidation of organic sulfur compounds to sulf1nic and sulfonic acids

Organic sulfur compounds such as disulfide, thiolsulfinate, thiolsulfonate, thiol, sodium thiolate, and sodium sultinale were readily oxidized to both sulfinic and sulfonic acids with superoxide anion generated from potassium superoxide and 18-crown-6-ether under mild conditions. However, both sulfide and sulfoxide did not react with superoxide anion, O₂^-. Although thiol was easily oxidized to disulfide with O₂^? at room temperature, it was oxidized further with O₂^? at 60° to the corresponding sulfinic and sulfonic acids. Symmetrical disulfide was obtained in the reaction of unsymmetrical thiolsulfinate or thiolsulfonate along with both sulfinic and sulfonic acids. Most reactive was thiolsulfinate which reacted at lower temperature ranging between ?40 and 0° to afford the products within 30 min. Relative reactivities fall in the following order: thiolsulfinate > thiolsulfonate > disulfide ? sodium thiolate ? sodium sulfinate. Polar solvents such as pyridine and acetonitrile were more effective than such a less polar solvent as benzene in the oxidation of the substrate, and increased amount of the crown ether shortened the reaction time. Nucleophilic attack of O₂^? and electron transfer processes are believed to be involved in these oxidations.     

Chemical studies on the anobiidae: Sex pheromone of the drugstore beetle, stegobium paniceum (L.) (coleoptera)

Chemical an spectroscopic evidence is presented to show that 2,3-dihydro-2,3,5-trimethyl-6-(1-methyl-2-oxobutyl)-4H-pyran-4-one (10) is the sex pheromone produced by the female drugstore beetle, Stegobium paniceum L.     

Cation analysis by thin-layer chromatography and reflectance spectroscopy : Part II. The determination of copper,nickel and zinc

A method has been developed whereby micro quantities of copper, nickel and zinc resolved on cellulose chromatoplates can be analyzed in situ by means of reflectance spectroscopy. Copper and nickel were determined in the presence of 11 other cations without any interference by employing neocuproine and dimethylglyoxime, respectively, as chromogenic reagents. In the case of zinc, the use of 3,3'-dimethyl-naphthidine was equally successful except in the presence of tin, cadmium and iron. Deviations to be expected when the procedure is employed routinely to determine nickel, copper and zinc, were estimated to be 2.1, 2.8 and 5.6%, respectively.     

Reactivity of n-aryl-α, α-dichlorinated arylketimines

N-Aryl-α,α-dichloroalkylarylketimines are formed from N-aryl-alkylarylketimines with N-chloro succinimide in carbon tetrachloride. Reaction of N-1-(2,2-dichlor-1-arylpropylidene)anilines with sodium methoxide the latter compounds formally involves migration of the notrogen atom from the 1- to the 3-position. The reaction of higher substituted N-aryl-α,α-dichloroalkylarylketimines with sodium methoxide leads mainly to α-chloro-α,β-unsaturated ketones. In the case of long-chain α,α-dichloroketimines, a formal γ-functionalization was observed. The reaction mechanisms are discussed in detail.     

Optical dephasing of the S1 ← S0 transition of free-base porphin in an n-decane host studied by photochemical hole-burning: a case of slow exchange

The homogeneous width and frequency of S₁ ← S₀ 0-0 transitions of free-base porphin in site B of n-decane are studied by photochemical hole-burning (T = 1.2–4.2 K). A localized phonon mode of 7 cm^?1 is identified as a phonon sideband and holes burnt into it yield a lifetime of 115 ± 20 ps. The results are consistent with the exchange model for slow exchange.     

Palladium-catalysed oxidation of alcohols with carbon tetrachloride,formation of 4,4,4-trichloro ketones from allylic alcohols and carbon tetrachlorid

Pd salts catalyse oxidation of alcohols with CCl₄ in the presence of K₂CO₃. Primary alcohols are oxidised to esters, and secondary alcohols to ketones. CCl₄ is converted to CHCl₃. The reaction of allylic alcohols bearing a terminal olefinic bond with CCl₄ or BrCCl₃ in the presence of palladium catalyst at 110° affords 4,4,4-trichloro ketones. At 40°, simple adducts of CCl₄ or BrCCl₃ having a halohydrin structure are obtained, which are converted to the corresponding trichloro ketones by the catalysis of palladium. Various halohydrins are converted to ketones by Pd catalysis.