Vibrational isotope effect of linear and planar molecules: Deuterated bromoethenes

Linear (planar) molecules A and B which are identical except for isotopic substitutions at the atomic sites are considered. Stretching (bending, out-of-plane) frequencies _k and normal modes _k of the isotopically perturbed molecule B are expressed in terms of stretching (bending, out-of-plane) frequencies _i and the corresponding normal modes _i of the unperturbed molecule A. Complete specification of the unperturbed normal modes is not required. All that is needed are stretching (bending, out-of-plane) amplitudes | _i of the normal modes _i at those sites that are affected by isotopic substitution. The rule which interlaces frequencies _k of molecule A with frequencies _i of molecule B is derived. Given two isotopic molecules A and B that differ by a single isotopic substitution at site , the inversion relation is derived. This relation expresses unperturbed stretching (bending, out-of-plane) amplitudes at the site in terms of stretching (bending, out-of-plane) frequencies of molecules A and B . As an example, out-of-plane vibrations of deuterated bromoethene were considered. In the simplest method 12 out-of-plane frequencies of four polydeuterated bromoethenes were calculated from 12 out-of-plane frequencies of bromoethene and three monodeuterated bromoethenes. Standard deviation of thus calculated frequencies from experimental frequencies is =2.74 cm^–1. In another method, 15 out-of-plane frequencies of four polydeuterated bromoethenes and selected monodeuterated bromoethene are calculated from 9 out-of-plane frequencies of bromoethene and the remaining two monodeuterated bromoethenes. Depending on which monodeuterated bromoethene is selected (1-, cis- or trans-), standard deviation of thus obtained frequencies from experimental frequencies is 1=2.84 cm^–1, c=2.96 cm^–1 and t=2.72 cm^–1.     

Vibrational isotope effect by the low rank perturbation method

Mathematical formalism of the low rank perturbation method (LRP) is applied to the vibrational isotope effect in the harmonic approximation. A pair of two n-atom isotopic molecules A and B which are identical except for isotopic substitutions at atomic sites is considered. Relations which express vibrational frequencies _k and normal modes _k of the perturbed isotopic molecule B in terms of the vibrational frequencies _i and normal modes _i of the unperturbed molecule A are derived. In these relations complete specification of the unperturbed normal modes _i is not required. Only amplitudes | _i of normal modes _i at sites affected by the isotopic substitution are needed.     

Dispersity and reducibility of the molybdenum oxide phase in SiO2, SiO2?Al2O3 and γ-Al2O3 supported molybdena catalysts

XRD, isothermal and temperature-programmed reduction (TPR) experiments were carried out with SiO₂, SiO₂–Al₂O₃ and -Al₂O₃ supported catalysts. Molybdena is in a more disperse state on supports containing more alumina and it is more reducible on SiO₂–Al₂O₃ than on SiO₂ or -Al₂O₃. TPR curves were shown to reflect connections between reduction kinetics and dispersity.

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-, , SiO₂, SiO₂–Al₂O₃ -Al₂O₃. , , SiO₂–Al₂O₃ SiO₂ -Al₂O₃. .

     

Copper(II)-disulphide interaction: a spectroscopic and electrochemical study of the interaction of copper(II) with an imidazole-containing disulphide

Summary The interaction of copper(II) salts with the imidazole-containing disulphide 5-(1,2,5-dithiazaepan-5-ylmethylene)-4-methyl-2-ethyl imidazole (MAMI) in MeOH have been investigated. The 11 Cu(ClO₄)₂MAMI system exhibited a single ligand field band at ca. 12200cm^-1, an intense shoulder at ca. 31500 cm^-1 and a less intense split feature at 24400 and 25300cm^-1 assignable to S() Cu^II and S() Cu^II charge transfer (CT) transitions, respectively. The e.p.r. parameters suggested the presence of a CuN₂SO chromophore, however; the 11 Cu(NO₃)₂MAMI system did not exhibit a S Cu^II CT band and the g value was comparatively high. An electrochemical study of the 11 Cu(ClO₄)₂MAMI system in MeOH revealed that the copper-disulphide interaction, though weaker, would confer a high redox potential as well as reversibility, similar to the copper-thioether interaction.     

Ethynylisopropylgermanes and Their Trimethylsilyl Derivatives

The reaction of ethynylmagnesium bromide with chloroisopropylgermanes (i-Pr_{4 - n} GeCl_{/sub> n} , n = 1-3) was used to prepare previously unknown ethynylisopropylgermanes i-Pr_{4 - n} Ge(CCH) _n (n = 1-3). The reaction of Me₃SiCCMgBr with i-PrGeCl₃ afforded i-Pr(Me₃SiCC)_{3 - n} GeCl _n (n = 1, 2). The reaction of the monochloride with BrMdCCH gave i-Pr(HCC)₂GeCCSiMe₃, while with the dichloride, i-Pr(HCC)·Ge(CSiMe₃)₂ formed. The latter compounds were obtained by independent synthesis from i-PrGe(CCH)₃, EtMgBr, and ClSiMe₃. The reaction of (bromomagnesioethynyl)triisopropylgermane with Me₃SiCl gave i-Pr₃GeCSiMe₃.     

Formation of methane in methanol synthesis on zinc-chromium catalysts

The rate of methane formation on zinc-chromium catalysts is described by zero-order rate law, If the catalyst is activated by copper, the rate of methane formation increases due to a decrease in the activation energy of the reaction. Presumably the formation of methane and methanol takes place on different active centers.

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, . , . , .

     

On the Interaction of Two Finite-Dimensional Quantum Systems

Interaction of quantum system S ^a described by the generalised × eigenvalue equation A| _s =E _s S ^a | _s (s=1,...,) with quantum system S ^b described by the generalised n×n eigenvalue equation B| _i = _i S ^b | _i (i=1,...,n) is considered. With the system S ^a is associated -dimensional space X ^a and with the system S ^b is associated an n-dimensional space X _n ^b that is orthogonal to X ^a . Combined system S is described by the generalised (+n)×(+n) eigenvalue equation [A+B+V]| _k = _k [S ^a +S ^b +P]| _k (k=1,...,n+) where operators V and P represent interaction between those two systems. All operators are Hermitian, while operators S ^a ,S ^b and S=S ^a +S ^b +P are, in addition, positive definite. It is shown that each eigenvalue _{k i} of the combined system is the eigenvalue of the × eigenvalue equation . Operator in this equation is expressed in terms of the eigenvalues _i of the system S ^b and in terms of matrix elements _s |V| _i and _s |P| _i where vectors | _s form a base in X ^a . Eigenstate | _k ^a of this equation is the projection of the eigenstate | _k of the combined system on the space X ^a . Projection | _k ^b of | _k on the space X _n ^b is given by | _k ^b =( _k S ^b –B)^–1(V– _k P})| _k ^a where ( _k S ^b –B)^–1 is inverse of ( _k S ^b –B) in X _n ^b . Hence, if the solution to the system S ^b is known, one can obtain all eigenvalues _{k i} } and all the corresponding eigenstates | _k of the combined system as a solution of the above × eigenvalue equation that refers to the system S ^a alone. Slightly more complicated expressions are obtained for the eigenvalues _{k i} } and the corresponding eigenstates, provided such eigenvalues and eigenstates exist.     

A π-acceptor series for phosphines from51V N.M.R. data on [η5-CpV(CO)3L] complexes

Summary Qualitative molecular orbital considerations of the complexes [⁵-CPV(CO)₃ L] (L = substituted phosphane, SbPh₃, AsPh₃, CN^–) suggest that s' V chemical shift parameters () obtained for these compounds should correlate with the -acceptor abilities of L. Based on observed r-values, the ligands are arranged in sequence of their -acceptor ability, which lies in the order P(OR)₃ > CN^– > PR'₃3 SbPh₃ PPhF₂ > P(i-Bu)₃ P(NR ₂ )₃ > PPh₃ > AsPh₃ Nuclear spin-spin coupling constants J (⁵¹V-³¹ P), line widths H and i.r. data in the (CO) region are also presented.P(OR)₃ = P(OEt)₃, 4-Ethyl-l-phospha-2,6,7-trioxabicyclo[2.2.2]-octane; R = Me, n-Pr; R = Me, Et.     

Thermal analysis of 1-Hydroxiethylidenediphosphonic acid and its salts

1-Hydroxyethylidenediphosphonic acid and its tetrasubstitutcd Li, Na, K, Rb, NH₄, Ca and Ba salts were synthcsized and their thermal behaviour was studied under non-isothermal conditions by simultaneous TG-DTG-DTA at 20–1000 C. The following thermal transformations were observed: loss of crystallization water, melting in the case of the acid, and intramolecular dehydration in the case of the salts, leading to the corresponding unsaturated derivatives. From the free acid, its acidic salts and the neutral ammonium salt, long-chain polycondensates are formed through intermolecular dehydration.

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Zusammenfassung 1-Hydroxyethyldiphosphonsäure und ihr Li-, Na-, K-, Rb-, NH₄-, Ca- und Ba-Salz wurden dargestellt. Ihr thermisches Verhalten wurde durch simultane TG-DTG-DTA unter nichtisothermen Bedingungen bei 20–1000 C untersucht. Folgende thermische Umwandlungen wurden beobachtet: Verlust von Kristallwasser, Schmelzen (nur bei der freien Säure), intramolekulare Wasserabspaltung (nur bei den Salzen) zu ungesättigten Verbindungen. Die freie Säure, die sauren Salze und das neutrale Ammoniumsalz bilden unter intermolekularer Wasserabspaltung langkettige Polykondensate.

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1- , , , , , . - . , , , . , , .

     

Intramolecular Mobility in the Complexes 2SbCl3· p-C6H4(CH3)2and SbCl3· C6H5COCH3according to 35Cl NQR Data

Temperature dependences of the ³⁵Cl and ¹²¹Sb spin-lattice relaxation time ₁in antimony trichloride complexes with p-xylene and acetophenone were studied using NQR spectroscopy. The activation energies of the retarded motion (similar to that discovered in some v complexes of SbCl₃) of chlorine atoms were determined from the ³⁵Cl ₁(T) function. New data on the shape of the ¹²¹Sb ₁(T) function are discussed.     

Conformational analysis of 2-phenyl-2-oxo-5,6-benzo-1,3,2-dioxaphosphepine with data from vibrational spectroscopy,dipole moments,and the kerr effect

2-Phenyl-2-oxo-5,6-benzo-1,3,2-dioxaphosphepine exists in a melt and solutions in polar solvents as a three-component equilibrium of two chair forms (C) with axial and equatorial arrangement of the phenyl group and the twist-boat form (TB) with a pseudoequatorial position of the phenyl substituent, a-C e-C e-TB. The two-component equilibrium e-C e-TB is observed in nonpolar solvents. The e-TB conformation occurs in the crystalline state. The dipole moment of the P=O groups is 3.5 D. The angle of rotation of the plane of the phenyl group with respect to the P=O bond in the e-TB conformation was 54 or 129.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, pp. 1039–1043, May, 1991.     

Thermal decomposition of Cu(I) phosphine complexes

The thermal decomposition of Cu(I) phosphine complexes of the general types (CuXPPh₃)₄, [CuX(PPh₃)₂] and [CuX(PPh₃)₃] was investigated.The thermal decomposition of (CuXPPh₃)₄, where X denotes Cl^–, Br^–, I^–, NO ₃ ^– and PPh₃=P(C₆H₅)₃, occurs with formation of a phosphine oxide intermediate. For the remaining complexes this intermediate was not proved in the thermal decomposition.

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Zusammenfassung Die thermische Zersetzung der Cu(I)-Phosphinkomplexe vom allgemeinen Typ (CuXPPh₃)₄ und [CuX(PPh₃)₂], wie auch [CuX(PPh₃)₃] wurde untersucht. Die thermische Zersetzung von (CuXPPh₃)₄, wobei X=Cl^–, Br^–, I^– und NO ₃ ^– bedeutet und PPh₃=P(C₆H₅)₃, verläuft unter Bildung eines Phosphinoxid Zwischenproduktes, bei den übrigen Komplexen konnte dieses im Laufe der thermischen Zersetzung nicht nachgewiesen werden.

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Résumé On a étudié la décomposition thermique des complexes phosphine-Cu(I) de formule générale (CuXPPh₃)₄, [CuX(PPh₃)₂], [CuX(PPh₃)₃]. La décomposition thermique de (CuXPPh₃)₄, où X désigne Cl^–, Br^–, I^– et NO ₃ ^– , et PPh₃=P(C₆H₅)₃, s'effectue avec formation d'un oxyde de phosphine intermédiaire; avec les autres complexes, cet intermédiaire n'a pas été mis en évidence au cours de la décomposition thermique.

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(CuXPPb₃)₄ [CuX(PPh₃)₂] [CuX(PPh₃)₃]. (CuXPPh₃)₄, X=Cl^–, Br^–, I^–, NO ₃ ^– , PPh₃=(₆₅)₃ . .

     

Some remarks on the periodical change of the stability constants of the lanthanide complexes

The correlations between the values of the lgK (K = stability constant of the lanthanide complex) and the reciprocal of the ionic radius 1/r or the sum of the ionization potentials ₁ ³ I for the lanthanide ions were reviewed for different ligands. A straight-line relationship (lgK – lgK)/lgK vs. (1/r – 1/r)/(1/r) or vs. ( ₁ ³ I – ₁ ³ I)/ ₁ ³ I was found within the tetrads La-Nd, Gd-Ho, and Er-Lu.

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Bemerkungen zum periodischen Wechsel der Stabilitätskonstanten von Lanthaniden-Komplexen

Zusammenfassung Es wurde eine Übersicht der Korrelationen zwischen den Werten von logK (K = Stabilitätskonstante der Lanthanidenkomplexe) und den reziproken Ionenradien 1/r oder der Summe der Ionisierungspotentiale ₁ ³ I für die Lanthanidenionen für verschiedene Liganden gegeben. Dabei wurde eine lineare Korrelation für (lgK – lgK)/lgK gegen (1/r – 1/r)/(1/r) oder gegen ( ₁ ³ I – ₁ ³ I)/_1/3 I innerhalb der Tetraden La-Nd, Gd-Ho und Er-Lu aufgefunden.

     

Pyrolysis of n-pentane on ZSM-5 zeolite

Pyrolysis of n-pentane has been studied at the temperature range 653–753 K on ZSM-5 zeolite. High catalytic activity and selectivity of H-ZSM-5 zeolite was found. The yield of propane was about 80 wt. %. A mechanism of the process is proposed.

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H-ZSM-5 n- 653–153 . . 80%. n-.

     

Statistical evaluation of the influence of several sample pretreatment methods on the mercury content detectable by chemical analysis of contaminated soil samples under practical conditions

The estimation of the environmental risk of contaminated sites caused by hazardous components may be obtained, for instance, by means of a soil survey. There unavoidable errors by sampling, sample preparation and chemical analysis occur. Furthermore, in case of mercury contaminations, the mercury content detectable by chemical analysis can be falsified, if between sampling, on the one hand, and sample preparation and sample decomposition for chemical analysis, on the other hand, volatile components or elementary metallic mercury escape from the sample. Thus, in these cases, handling of samples such as air drying, storing in plastic bags or thermal evaporation, generally termed sample pretreatment, is a further source of error in evaluating a material. However, the measuring results are influenced not only by sampling, sample pretreatment, sample preparation by homogenization and splitting, and chemical analysis; they must also reflect the intrinsic properties of the soil sample subject to both global fluctuations and local heterogeneities. The present work shows by example of a non-uniformly contaminated site to what extent the analytically detectable mercury content is changed by the method of handling of soil samples in the period between sampling and chemical analysis. A hierarchical experimental design was realized in order to separately quantify the different sources of variation of the measured mercury contents, which are caused by global variations, local heterogeneities, sample preparation, sample pretreatment as well as chemical analysis. As turned out by variance analysis, the variance portion contributed to the total variance by sample pretreatment is highly significant and lies in the same order of magnitude as the variance caused by local heterogeneities of the soil. That means that the type of sample pretreatment influences the analytical results essentially. In order to quantify the effect of a definite pretreatment method in comparison with the mercury content of the unchanged original soil sample, the probable systematic error of a method was introduced. Investigations were only carried out at two sampling locations of the contaminated site because of the relatively high labour; the mean values and variances obtained cannot be immediately transferred to other sites. However, the general knowledge can be used as methodical basis for further investigations. Particularly, the consequence arises that the regulations existing for the treatment of mercury-contaminated samples between sampling and chemical analysis must be revised to obtain comparable criteria of evaluation.Symbols used level of error in statistical tests, - _i random effect of the i-th sampling location with respect to the mercury content, effect of global fluctuations - _ij random effect of the j-th primary sample (composite sample) at the i-th sampling location, effect of local heterogeneity, sampling error - _ijk random effect of the k-th subsample within the respective j-th primary sample (composite sample) at the i-th sampling location, sample preparation error - _ijkl random effect of the l-th pretreated sample belonging to the respective k-th subsample of the j-th primary or composite sample at the i-th sampling location, sample pretreatment effect - _1– probable relative systematic error of a pretreatment methods as compared with the original material at the coverage probability 1– - overall expected mercury content of the sampling results - _i expected mercury content of the i-th pretreated composite sample at a fixed location - û_{1.1 –} lower limit of a confidence interval for the unknown expected mercury content of unchanged original material at the confidence probability 1– - _i intraclass correlation coefficient - ² , ² , ² , ² , _Z ² variance components caused by global variability, local heterogeneity, sample preparation, sample pretreatment and analytical error, respectively - _total ² total variance of mercury content - D² operator of the variance of a random variable - E operator of the mathematical expectation of a random variable - F_i mean squared sum quotient of the Fisher's F-distribution - F_1–/2(fg_i, fg_j) critical value of the F-distribution at fg_i and fg_j degrees of freedom, respectively - fg_i degree of freedom of a (mean) sum of squared deviations - H_i hypothesis regarding a statistical law - I_1– confidence interval for the unknown expected value difference of two methods compared at the probability 1–, probable systematic error of a pretreatment method as compared with the unchanged original material at the coverage probability 1– - MQ_i, mq_i mean squared deviations as explained in the context - n_i number of sampling locations, primary samples per location, subsamples per primary sample, pretreatment methods and measuring values per pretreated sample, respectively - S _i ² , s _i ² variance estimation obtained by chemical analysis - SQ_i, sq_i sum of squared deviations - S(|Y₁–Y_i|) mean error of the absolute mean value difference |Y₁–Y_i|) - t_1–/2;m critical value of the Student's t-distribution at m degrees of freedom and the probability 1–/2 - Y_ijklm mercury content obtained on the m-th final sample of the l-th pretreated sample belonging to the k-th subsample of the j-th primary sample at the i-th sampling location - Y_i, y_i,... mean values obtained by sampling and chemical analysis - Z_ijklm random error of the ijklm-th measuring value (final sample value) Y_ijklm.     

A General Analysis of Field-Based Molecular Similarity Indices

A formalism is presented that incorporates the entirety of all field-based molecular similarity indices of general form S _ij = _ij /h( _ii , _jj ), where the numerator is given by the inner product or overlap of field functions F _i and F _j corresponding to the ith and jth molecules, respectively, and the denominator is given by a suitable mean function of the self-similarities _ii and _jj . This family of similarity indices includes the index initially introduced by Carbó nearly twenty years ago, where h( _ii , _jj ) is taken to be the geometric mean of _ii and _jj , and the well-known indices due to Hodgkin and Richards, and Petke, where h( _ii , _jj ) is taken to be the arithmetic mean and maximum of _ii and _jj , respectively. Two new indices based upon the harmonic mean and minimum of _ii and _jj are also defined, and it is demonstrated that the entire set of field-based similarity indices can be generated from a one-parameter family of functions, called generalized means, through proper choice of the parameter value and suitable limiting procedures. Ordering and rigorous bounds for all of the indices are described as well as a number of inter-relationships among the indices. The generalization of field-based similarity indices, coupled with the relationships among indices that have been developed in the present work, place the basic theory of these indices on a more unified and mathematically rigorous footing that provides a foundation for a better understanding of the quantitative aspects of field-based molecular similarity.     

Study of interaction between trimethyl-substituted silanes and silica surface

Interaction mechanism of (CH₃)₃SiX silanes (X=Br, I, N₃, NCS, NCO, CN, NCNSi(CH₃)₃ and SO₄Si(CH₃)₃ with dehydrated silica surface has been studied by IR spectroscopy. It has been established that (CH₃)₃SiCN, (CH₃)₃SiBr, (CH₃)₃SiI and [(CH₃)₃Si]₂SO₄ can be used as soft silylating agents for endcapping.

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(CH₃)₃SiX (X=Br, I, N₃, NCS, NCO, CN, NCNSi(CH₃)₃, SO₄Si(CH₃)₃) -. , (CH₃)₃SiCN, (CH₃)₃SiBr, (CH₃)₃SiI [(CH₃)₃Si]₂SO₄ .

     

Kinetics and mechanism of acetylene hydromethylation on organonickel catalysts

Kinetics of methane interaction with acetylene on Ziegler-Natta type organonickel catalysts has been studied. The reaction is first order with respect to methane. The kinetic isotope effect amounts to K_{CH 4}/K_{CD 4}=1.5 and K_{C 2}H₂,CH₄,H₂/K_{C 2}D₂,CD₄,D₂=2.0.

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-. -. K_{CH 4}/K_{CD 4}, K_{C 2}H₂,CH₄,H₂/K_{C 2}D₂,CD₄,D₂ 1,5; 2,0. .

     

Analysis of the Impedance Frequency Spectrum of a Passive Iron Electrode by Combined Impedance and Photoadmittance Measurements

The frequency spectra of electrochemical impedance Z, photocurrent i, and photopotential E are obtained for a passive Fe electrode in 0.2 M KOH in a frequency range 1.3 to 8300 Hz. The validity of relationship E/i = –Z is proved experimentally. The oxide film impedance Z _F is calculated from the frequency spectrum of E with expression Z _F = –E/g. The generation current g is found from the photocurrent frequency spectrum. The frequency impedance spectrum Z _F/S of the oxide/solution interface is determined with equation Z _F/S = Z – Z _F – R _el, where R _el is the solution resistance.     

Zwitterionic [(H3NCH2C≡CC≡CCH2NH3)]Cu2Cl4 π-Complex: Template Synthesis and Crystal Structure

Crystals of the [(H₃NCH₂CCCCCH₂NH₃)]Cu₂Cl₄ -complex, formed in the oxidative dimerization of propargylammonium cations, were obtained by ac electrochemical synthesis from CuCl₂ · 2H₂O and propargylammonium chloride ([CCCH₂NH₃]Cl) and studied by X-ray diffraction analysis (DARCh automated diffractometer, MoK radiation, /2 scan mode; 2275 reflections with F 4(F), R = 0.048). Crystals are monoclinic: space group B2/b, a = 19.591(6) Å, b = 7.299(3) Å, c = 8.636(3) Å, = 106.83(3)°, Z = 4. The structure consists of individual [(H₃NCH₂CCCCCH₂NH₃)]Cu₂Cl₄ moietes united through the elongated Cu···Cl contacts (2.827(5) Å) into chains oriented along the [010] direction. The bond of the centrosymmetric propargylammonium dimer is -coordintated by copper(I) atom and is elongated to 1.227(6) Å.