S42+ and S42− : an ab initio study

The structures of S₄²⁺ and S₄^2? have been investigated by ab initio calculations using the GAUSSIAN 70 system of programs and the 44-31G basis set. Electronic singlet states of the square form and three possible conformations of the chain structure were examined for both ions, and the singlet rectangle form of S₄^2? was also investigated. The anti chain form of S₄²⁺ was found to be 78.3 kJ mol^? more stable than the square form, in contrast to previous experimental data. S₄^2?is predicted to adopt the chain structure with the anti conformation.     

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.     

On the ab initio evaluation of the solvent shift of electronic absorption spectra

Solvent shift in water of π → π^* transitions of the carbonyl group is evaluated making use of a recently proposed computdtional procedure for the continuum solvent model. Comparisons with the discrete model and with composite discrete-continuum procedures are performed.     

An ab initio MO calculation of the electronic structure and geometry of protonated methanol

Protonated methanol, CH₃ OH₂⁺, has been studied using the LCAO—MO—SCF method with a 7, 3 and 9, 5, 1 Gaussian orbital basis set on the heavy atoms and 4s on hydrogen. It is found that the ground state is non-planar around oxygen, in contrast with previous calculations, with an inversion barrier of 3 kcal mol^?1. The changes in electron distribution in the reacting systemCH₃⁺ + H₂O → CF₃OH₂⁺is also examined.     

Ruthenium(II) complexes with mono and ditertiary arsines and phosphines and their reaction with small molecules

Dichlorotetrakis(dimethylsulphoxide)ruthenium(II) reacts with AsPh₃ AsMePh₂, AsMe₂Ph and SbPh₃ in ethanolic hydrochloric acid solution to yield the complexes RuCl₂(DMSO)₂(AsPh₃)₂, RuCl₂(DMSO) L₂ (L = AsMePh₂, AsMe₂Ph, SbPh₃) respectively. The treatment of ruthenium(II) blue solution with AsMePh₂, AsMe₂Ph and SbPh₃ in alcohol resulted in the formation of the complexes; RuCl₂L₃ (L = AsMePh₂, AsMe₂Ph and SbPh₂), respectively. The reaction of RuCl₂(DMSO)₄ with the bidentate ligands 1,2 bis (diphenylarsino)methane (DPAM), 1,2 bis(diphenylarsino)ethane (DPAE) and 1,2 bis (diphenylphosphino)methane (DPPM). 1,2 bis(diphenylphosphino)ethane (DPPE), in ethanol gave the complexes RuCl₂(DPAM)₂, RuCl₂(DPAE)₂, RuCl₂ (DPPM)₂ RuCl₂(DPPE)₂, respectively. The complexes thus obtained undergo reaction with carbon monoxide, hydrogen, molecular nitrogen and nitric oxide to yield a variety of mixed ligand complexes.     

An ab initio SCF study of the rotational isomerism in ethyl formate and propargyl formate

SCF computations using STO/3G orbitals have been made for methyl formate, ethyl formate and propargyl formate in order to investigate rotational isomerism in the last two molecules. The results are in good agreement with those of IR and microwave studies.     

Properties of the X 1Σ state of BF

A perturbation theoretical approach for treating electron correlation has been used to calculate the potential energy curve and dipole moment function of BF near its equilibrium bond length. A dipole moment of 0.89 D (B^?F⁺) is predicted at R_e. When the bond is stretched by ≈0.2 Å the dipole reverses sign.     

Vibrational spectroscopy at very high pressures: Part 21. Raman and infrared study of mercury(II) iodide [1]

The solid phase behaviour of HgI₂ is reviewed, together with IR and Raman data for the red and the high-temperature yellow forms. New IR transmission, single-crystal reflectance, and Raman data were obtained at temperatures down to 80 K for red HgI₂ but no evidence of a temperature-induced transition to HgI₂ IV was found.The high pressure results showed a possible break in the slope of the pressure versus frequency plot for the 29 cm^?1 Raman mode of red Hgl, at 6 ± 0.5 kbar, close to the reported III/IV phase boundary. Both Raman and far-IR spectra of the high pressure form of yellow HgI₂ differ significantly from those of high temperature yellow HgI₂ : the two forms are regarded as having different structures. These, and other data, reveal a much closer similarity between the phase diagrams of HgBr₂ and HgI₂ than has been suspected hitherto.     

The structure analysis of triaryl derivatives of the group V elements: V. Spectra,crystal and molecular structure of trimesitylarsine,C27H33As

The complete X-ray structure analysis of trimesitylarsine (TMAS), C₂₇H₃₃As, has been performed. The crystals are triclinic, a 18.718, b 16.418, c 8.204 Å, α 99.99, β 97.85, γ 104.56°, Z = 4, space group P1̄ (two independent molecules in the asymmetric unit); the final value of the R-factor is 0.038. In the electronic spectrum of TMAS the long-wave band has the maximum at 276 nm which differs significantly from that of triphenylarsine (TPAS) at 249 nm. The bathochromic spectral shift and the molecular conformation are caused by the steric effects as a result of bulky methyl groups in the positions 2,4 and 6 in the phenyl rings. Two independent molecules are connected by a pseudo-axis of symmetry.     

Studies in sesquiterpenes—LVIII : Deodardione,a sesquiterpene diosphenol and,limonenecarboxylic acid,a possible norsesquiterpene—compounds from the wood of cedrus deodara loud.

Isolation and structure elucidation of a C₁₁ mono-carboxylic acid, apparently a nor-sesquiterpene, and, a sesquiterpene diosphenol from the essential oil of Cedrus deodara Loud. are described.     

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.     

1-dicarboxymethylaminomethyl-2-hydroxy-3-naphthoic acid as a sensitive and selective fluorimetric reagent for beryllium,and for lanthanum and lutetium in presence of the other lanthanides

1-Dicarboxymethylaminomethyl-2-hydroxy-3-naphthoic acid (DHNA) forms fluorescent complexes with Al, Be, Ga, Hf, In, La, Lu, Mg, Sc, Th, Y, and Zr. The Be, La and Lu complexes have a metal : ligand ratio of 1:1. The beryllium complex shows maximal fluorescence at pH 6.8 with excitation-fluorescence maxima at 360 and 450 nm; linear calibration curves are obtained in the range 0.09–1.8 μg Be. In the presence of the calcium-EDTA complex, of 25 cations studied, only > 100-fold molar ratios of aluminium and > 10-fold molar ratios of magnesium and scandium caused interference in the determination of 0.1 μ mole of beryllium. Amongst 15 anions, > 100-fold molar ratios of phosphate, > 50-fold molar ratios of arsenate or oxalate and > 10-fold molar ratios of citrate, fluoride and tartrate caused low results. Lanthanum and lutetium can be determined at PH 10 and 370/460 nm in the range 7–28 μg even in the presence of a 3-fold molar ratio of the other lantlianides without interference.     

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.     

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.     

Ab initio calculation of the dipole moment function of hydrogen iodide

SCEP/CEPA and MC SCF potential energy and dipole moment functions for hydrogen iodide have been calculated. Spectroscopic constants and vibrational dipole matrix elements obtained from the CEPA functions are in good agreement with experimental data. In contrast to previous results for hydrogen fluoride, the MC SCF dipole moment function is less accurate than the CEPA function.     

Studies on lanthanoid sulphites: Part IV. Thermal decomposition of erbium sulphite trihydrate under various experimental conditions

Thermal behaviour of Er₂(SO₃)₃· 3H₃O has been studied by means of TG, DTG, DTA, DSC and EGA techniques. Experimental conditions were also varied, $\text{viz.}$ sample size, heating rate and the atmosphere.The dehydration starts slowly above 150°C but the release of water is rapid around 250°C. SO₂ gas is evolved slowly and simultaneously with H₂O. The anhydrous sulphite is formed below 300°C after which it decomposes through several reactions accompanied by a release of mainly SO₂, but also a small amount of SO₃ near 650°C. In air, there is a clear plateau in the TG curve between 600 and 800°C; the weight loss involved depends strongly on the sample size and heating rate, however. A plausible explanation for the plateau is the formation of a mixture of Er₂(SO₄)₃, Er₂O(SO₄)₂ and Er₂O₂SO₄. The next plateau around 900 – 1000°C corresponds to Er₂O(SO₄)₂ and Er₂O₂SO₄. In nitrogen atmosphere, the first plateau after the anhydrous sulphite appears later in the weight scale as compared to air. Although the position of the plateau corresponds to the sesquisulphide, it is according to X-ray diffraction results a mixture of Er₂O₂(SO₄) and Er₂O₃. In both air and nitrogen, the final reaction step above 1000°C is the formation of Er₂O₃.     

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.     

Molecular mobility of spin-labelled terephthaloyl chloride and 1,10-decanediol copolymer in solution

Intramolecular mobility of spin-labelled terephthaloyl chloride and 1,10-decanediol copolymer in solution was investigated using a polymer in which the label was rigidly attached to the main chain methylene groups. Correlation times and effective segmental dimensions were measured, as were the frequency and amplitude of the high-frequency torsional vibrations of the main chain monomer units. The amplitude of high-frequency torsional vibrations was shown to increase with increasing temperature.     

Studies in sesquiterpenes—LIII : Deodarone and atlantolone,new sesquiterpenoids from the wood of Cedrus deodara loud

Isolation and structure determination of a novel bisabolane-based tetrahydro-γ-pyrone from the essential oil from the wood of Cedrus deodara Loud is described. The compound, which has been named deodarone, has been chemically correlated with the sesquiterpene ketone, atlantone. An hydroxy ketone, designated as atlantolone, has also been isolated. This compound appears to be the precursor of the new C₁₂-ketone, recently described as a component of the essential oil of Cedrus atlantica Manet.     

Studies in sesquiterpenes—LII: Isohimachalone: a constituent of the essential oil from wood of Cedrus deodara loud

Isolation and structure elucidation of a new bicyclic sesquiterpene of a new carbo-skeleton, from the essential oil from the wood of Credrus deodara loud., is reported. The structure rests on a direct correlation with β-himachalene.