Physicochemical studies on solid products of reactions of chromyl chloride and chromyl acetate with alkylaromatics. Part I. Infrared spectra and magnetic measurements

Summary Reaction of chromyl chloride, CrO₂Cl₂, with various alkylaromatics leads to solid products of composition 2CrO₂Cl₂ · HR (where HR is an alkylaromatic); however, they are not the simple adducts as the oxidation state of chromium appears to be reduced from VI to IV. The products of chromyl acetate reactions with the same hydrocarbons are monochromo(IV)- and dichromo(IV)-hydroxyacetates depending on the method of preparation. Infrared spectra and magnetic measurements were interpreted as showing that none of these compounds are the adducts of chromyl chloride or chromyl acetate but that all contain chromium(IV).     

Theoretical investigation of internal conversion in chromyl chloride

The internal conversion process from single vibronic levels in the first excited electronic state S₁ of chromyl chloride was theoretically investigated. On the basis of this analysis certain important features of the experimentally observed fluorescence decay from S₁ have been understood. Implications of the obtained results to multiphoton chemistry are discussed.     

Some aspects of the polymerization of n-butyl vinyl ether by chromyl chloride

The rate of n-butyl vinyl ether polymerization by chromyl chloride is first order in [catalyst] and second order in [monomer]. Added H₂O (after a certain concentration) and HCl increase the rate, thiophene retards the rate, while pyridine inhibits the rate. DP is independent of [chromyl chloride] and increases with increasing [monomer] up to 1M, thereafter becoming independent of it. Both rate and DP increase over the range 10?32°C and decrease at higher temperatures.     

Über den Mechanismus der Bildung von Chrom(IV)-oxid aus Chromylchlorid

On the Mechanism of the Formations of Chromium(IV)oxide from Chromyl Chloride The decomposition of chromyl chloride in the temperature range from 380 to 400°C leads with increasing oxygen pressure to chromium oxides containing up to nearly 90% of CrO₂. The interaction with the chlorine prevents a quantitative formation of CrO₂. Up to 315°C during the decomposition of chromyl chloride chromium oxides of higher valencies are formed separating chlorine and taking up oxygen simultaneously. By working in flowing oxygen it could be proved that the decomposition goes at lower temperatures via the nondetectable CrO₃. By heating gradually and by removing the chlorine as far as possible stoichiometric CrO₂ at oxygen pressures above 60 atm could be obtained.     

Étard reaction—III Oxidation of N-propylbenzene and methylcyclohexane with chromyl chloride

Étard oxidation of n-propylbenzene yields a number of products among which benzaldehyde, methyl benzyl ketone, propiophenone, 1-chloro-1-phenylpropane, 1-phenylpropan-1-ol, 1-phenyl-1-chloropropan-2-one and 1-phenyl-2-chloropropan-1-one were identified. The same products were obtained by treatment of 1-phenylpropene and 1,2-epoxy-1-phenylpropane with chromyl chloride. Presumably all these compounds result from a common intermediate possessing an epoxide like structure. The oxidation by chromyl chloride of methylcyclohexane also leads to a larger number of products than previously known, namely: 1-methyl-1-cyclohexanol, hexahydrobenzaldehyde, 1-methylcyclopentylaldehyde, 2-methylcyclohexanone and 1-methyl-1-chlorocyclohexan-2-one. The last three compounds were produced also in the reaction of 1-methylcyclohexene with chromyl chloride. The mechanism of these reactions is discussed.     

Trapping of an Organic Radical by an O=CrVI Function

Not only capable of generating organic radicals by H abstraction, chromyl chloride can also trap them again (see scheme). This is confirmed by the crystal structure of a Cr^V oxo alkoxide, which was formed in three successive steps when bisadamantylidene oxide was allowed to react with CrO₂Cl₂.     

Reaction of fluoroole fins with chromyl chloride

Conclusions The reactions of chromyl chloride with various fluoroolefins were investigated. The character of the process does not agree with the mechanism suggested for the reaction of chromyl chloride with olefins not containing halogen atoms at the double bond.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 379–383, February, 1970.     

Mechanism of chromyl chloride epoxidation

Modern electronic structure methods including complete active space perturbation theory to second order (CASPT2), and a range of density functional (DFT) methods are used to characterize the intermediates and transition states associated with ethylene epoxidation by chromyl chloride. A novel zwitterionic direct addition pathway is characterized which, when coupled with a dinuclear complex, exothermically produces epoxide through a pathway with a small kinetic barrier.     

Photoelectron spectrum and ground state electronic structure of chromyl chloride vapor

The electronic structure of chromyl chloride CrO₂Cl₂ has been investigated by ultraviolet (HeI) photoelectron spectroscopy. Mulliken-Wolfsberg-Helmholtz molecular orbital calculations have been performed in order to provide a model for interpretation of the photoelectron spectra and to assist in assigning the low-energy optical absorption and emission transitions. The first ionization potential of CrO₂Cl₂ at 11.8 eV is due to ionization of the near-degenerate oxygen and chlorine nonbonding 2a₂, 4b₁, and 4b₂ MO's. The first unoccupied orbital is basically a chromium dπ^* orbital. The excitations (2a₂, 4b₁, 4b₂)→ 7a₁^* correlate well with the three low energy absorption transitions observed.     

Collisionless infrared multiphoton production of electronically excited parent molecules

In the absence of collisions chromyl chloride (CrO₂Cl₂) shows orange fluorescence when the parent molecule is irradiated by the focused output Time-resolved fluorescence is investigated over the pressure range 5 × 10^?4 to 15 torr. As the pressure is increased, a secondary collision-ind We interpret the collisionless part of the emission to arise from infrared transitions between the high vibrational levels of the ground state and the     

Mechanism of chromyl chloride alkane oxidation

Modern electronic structure methods, including complete active space-perturbation theory to second order (CASPT2) and a range of density functional (DFT) methods, are used to characterize the intermediates and transition states associated with chromyl chloride alkane oxidation. Computed energetics for radical abstraction are found to be inconsistent with experimental activation energetics. The alcohol product is also found to be too endothermic to be viable. A novel zwitterionic direct pathway is characterized which, when coupled with a dinuclear complex, exothermically produces alcohol consistent with experiment.     

An improved spectrophotometric determination of chloride via chromyl chloride formation

Chloride (? 1 μg) is extracted into carbon tetrachloride as chromyl chloride. It is back-extracted into pH 3.2 buffer where it oxidizes iodide to tri-iodide ions, which are measured at 288 nm or 351 nm. The relative standard deviation is 0.8% for 10 μg of chloride.     

Determination of lead in stainless steel by atomic-absorption spectroscopy

A method has been developed for the determination of lead in stainless steels by atomic-absorption spectrometry after removal of iron by solvent extraction and volatilization of chromium as chromyl chloride. The method proposed is suitable for the determination of lead in the range from 5 to 100 ppm.     

A new technique for the identification of chloride ions by the formation of chromyl chloride

Summary A new technique is described for the identification of the chloride ion through the formation of chromyl chloride, based on the extraction of the latter with carbon tetrachloride. The identification limit is 2g of chloride. It is possible to carry out the test in the presence of many other anions, including fluoride, which cannot be present when the traditional distillation technique is employed.

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Zusammenfassung Vorgeschlagen wird eine neue Technik zum Chloridnachweis durch Bildung von Chromylchlorid. Dieser Nachweis beruht auf der Extraktion des Chromylchlorids mit Tetrachlorkohlenstoff. Die Nachweisgrenze liegt bei 2g Chlorid, wobei die Möglichkeit besteht, den Test auch in Gegenwart von Fluorid durchzuführen, das bei Anwendung der üblichen Destillationsmethoden nicht anwesend sein darf.

     

First-principles study of structural,elastic, electronic and optical properties of perovskites XCaH3 (X = Cs and Rb) under pressure

The stability, structural parameters, elastic constants, electronic and optical properties of perovskites CsCaH₃ and RbCaH₃ were investigated by the density functional theory. The calculated lattice parameters are in agreement with previous calculation and experimental data. The energy band structures, density of states, born-effective-charge and Mulliken charge population were obtained. The perovskites CsCaH₃ and RbCaH₃ present a direct band gap of 3.15 eV and 3.27 eV at equilibrium. The top of the valence bands reflects the s electronic character for both structures. Furthermore, the absorption spectrum, refractive index, extinction coefficient, reflectivity, energy-loss spectrum, and dielectric function were calculated. The origin of the spectral peaks was interpreted based on the electronic structures. The static dielectric constant and refractive index are indeed, inverse proportional to the direct band gap.     

DFT calculation of the chromyl nitrate, CrO2(NO3)2 The molecular force field

We have carried out a structural and vibrational theoretical study for chromyl nitrate. The density functional theory has been used to study its structure and vibrational properties. The geometries were fully optimised at the B3LYP/Lanl2DZ, B3LYP/6-31G* and B3LYP/6-311++G levels of theory and the harmonic vibrational frequencies were evaluated at the same levels. The calculated harmonic vibrational frequencies for chromyl nitrate are consistent with the experimental IR and Raman spectra in the solid and liquid phases. These calculations gave us a precise knowledge of the normal modes of vibration taking into account the type of coordination adopted by nitrate groups of this compound as monodentate and bidentate. We have also made the assignment of all the observed bands in the vibrational spectra for chromyl nitrate. The nature of the Cr-O and Cr<--O bonds in the compound were quantitatively investigated by means of Natural Bond Order (NBO) analysis. The topological properties of electronic charge density are analysed employing Bader's Atoms in Molecules theory (AIM).     

Determination of vanadium in high alloy steels by isotope-dilution

An isotope-dilution method has been developed for the determination of vanadium in high-alloy steels. Vanadium is titrated amperometrically after removal of chromium as chromyl chloride. Vanadium losses due to adsorption were corrected for radiometrically. The procedure was tested on N.B.S. steel samples and showed good precision and accuracy.     

Origin of the insulating state in NaCuO2

We study the electronic structure of NaCuO₂ by analysing experimental core level photoemission and X-ray absorption spectra using a cluster as well as an Anderson impurity Hamiltonianincluding the band structure of the oxygen sublattice. We show that the X-ray absorption results unambiguously establish a negative value of the charge transfer energy, Δ. Further, mean-field calculations for the edge-shared one-dimensional CuO₂ lattice of NaCuO₂ within the multiband Hubbard Hamiltonian show that the origin of the insulating nature lies in the band structure rather than in the correlation effects. LMTO-ASA band structure calculations suggest that NaCuO₂ is an insulator with a gap of around 1 eV.     

Z-scan analysis and ab initio studies of β-BaTeMo2O9 single crystal

The Z-scan measurements for the non-centrosymmetric optical crystals β-BaTeMo₂O₉ (BTMO) were performed. The corresponding experiments were carried out using the 5 ns pulses of the second harmonic of a nanosecond Nd:YAG laser at the 532 nm wavelength. It was shown that the studied crystals possess promising third-order optical susceptibilities, which allow to use the crystal as optical limiters. The comparison with other oxide materials is presented. To clarify the origin of the observed effect, the electronic and optical properties of BTMO were calculated using the density functional theory (DFT)-based method. The performed calculations of the electronic and optical properties revealed certain peculiar features that can be suitable for the nonlinear optical applications. The relation between the observed nonlinear optical features and the calculated band structure is emphasized. The values of the calculated band gap and refractive index for β-BaTeMo₂O₉ are also reported.     

Energy band genesis from sublattice states in MgSiN2 and MgGeN2 crystals

The electronic structure of MgSiN₂ and MgGeN₂ orthorhombic crystals and their sublattices was analyzed at the density functional theory level using the sublattice method. The energy-band structure of the orthorhombic crystals is compared to the structure of their hypothetic analogues with the chalcopyrite lattice. The origin of the specific features of the valence band structure from the sublattice states is determined in the studied crystals, which is mainly due to the interaction of atoms in SiN₄ and GeN₄ cation tetrahedra.