Infrared spectra and theoretical study ofE-3-(2-R-vinyl)-2-benzothiazolinones

The C=O stretching frequencies ofE-3-(2-R-vinyl)-2-benzothiazolinones (1 a–1 p) were measured in CCl₄ and CHCl₃ and correlated with ⁺ and * substituent constants. Thev(C=O) vs * (R) correlation was compared to an analogical relationship obtained with 3-R-2-benzothiazolinones (2). The electronic structure and geometry of compounds was investigated by CNDO/2 and PCILO methods. The results of both the spectral and theoretical studies showed forE-3-(2-R-vinyl)-2-benzothiazolinones a preference of the N—C-s-cis conformation (3), in which the substituent effects are transmitted to the C=O group very efficiently. The transmission factor for the CH=CH group was determined according to the definition ofJaffé. The role of inductive effects, delocalization of the nitrogen lone-pair electrons as well as the through-space interaction between the C=O and C=C bonds is discussed in terms of transmission mechanism and structural properties.

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Infrarotspektren und theoretische Untersuchungen vonE-3-(2-R-vinyl)-2-benzo-thiazolinonen

Zusammenfassung Es wurden die C=O-Streckfrequenzen vonE-3-(2-R-vinyl)-2-benzothiazolinonen (1 a–1 p) in CCl₄ und CHCl₃ gemessen und mit -, ⁺- und *-Substitutionskonstanten korreliert. Diev(C=O)-*-Korrelation wurde mit einer analogen Beziehung für 3-R-Benzothiazolinonen (2) verglichen. Die elektronische Struktur und die Geometrie der Verbindungen wurden mittels CNDO/2- und PCILO-Berechnungen untersucht. Es ergab sich dabei sowohl aus den spektros-kopischen als auch aus den theoretischen Ergebnissen eine N—C-s-cis-Konformation (3) für dieE-3-(2-R-vinyl)-2-benzothiazolinone, da dies eine günstige Geometrie zur Übermittlung von Substitutionseffekten zur C=O-Gruppe ergibt. Der Transmissionsfaktor für die CH=CH-Gruppe wurde nach der Definition vonJaffé bestimmt. Die Rolle von induktiven Effekten, der Delokalisierung des freien Elektronenpaares am Stickstoff und der C=O....C=C-Wechselwirkungen durch den Raum wurde auf Basis von Transmissionsmechanismen und strukturellen Eigenschaften diskutiert.

     

Substituent dependence of the d-d transition band in the electronic absorption spectra of arylferrocenes and the corresponding arylferricenium salts

The electronic absorption spectra of 22 arylferrocenes and their arylferricenium salts with pentacyanopropenide (PCNP) were recorded. The attemptedHammett correlation of _max of the d-d transition bands of arylferrocenes revealed that this band is substituent dependent only for strong electron-withdrawing substituents. Excellent correlation of _max of the d-d transition bands with ⁺ constants was found in the case of arylferricenium cations. Good correlations of _max was also found with theE _1/2 oxidation potentials measured by cyclic voltametry.

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Substituentenabhängigkeit des d-d-Überganges in den Elektronenabsorptions-Spektren von Arylferrocenen und entsprechenden Arylferricenium-Salzen

Zusammenfassung Elektronenabsorptions-Spektren von 22 Arylferrocenen und ihren Arylferricenium-Pentacyanopropenid-Salzen wurden gemessen. VersuchteHammett-Korrelationen des längstwelligen d-d-Überganges (_max) zeigten, daß diese Bande nur von stark elektronenanziehende Substituenten abhängig ist. Im Fall der Arylferricenium-Kationen wurde eine ausgezeichnete Korrelation zwischen _max der d-d-Bande und den ⁺-Konstanten festgestellt. Eine gute Korrelation der _max-Werte wurde auch mit denE _1/2 Oxidationspotentialen gefunden, die durch cyclische Voltametrie meßbar sind.

     

Intensity of the η(C≡C) Bands in the IR Spectra of Acetylene Derivatives and σR 0 Constants of Organosilicon,Organogermanium, and Organotin Substituents

The integral absorptivities of shape-characteristic (CC) bands in the IR spectra of 66 acetylene derivatives RCCX (R = H, Me₃M; X are inorganic and organic substituents) are related by a common linear equation to the _R ⁰ constants of the R and X substituents. The _R R⁰ constants of 10 Alk₃M substituents were calculated. The _R ⁰, _R , and _R ⁺ constants of Me₃M substituents were analyzed. The positive _R ⁰ values (0.12, 0.06, and 0.04 for R = Si, Ge, and Sn, respectively) suggest that in the ground electronic state of Me₃MCCX molecules the resonance acceptor effect of the Me₃M substituents (d, conjugation) prevails over donor (, conjugation). The first effect attenuates and the second enhances as the atomic number of M increases.     

S N H reactions of pyrazine N-oxides and 1,2,4-triazine 4-oxides with CH-active compounds

Nucleophilic substitution of hydrogen in pyrazine N-oxides under the action of CH-active compounds requires activation with acylating agents. This activation facilitates aromatization of intermediate ^H adducts via elimination of the acid residue to form substituted pyrazines. More electrophilic 1,2,4-triazine 4-oxides react with carbanions derived from CH-active compounds without additional activation according to a scheme, which has previously been unknown for azine N-oxides. This scheme involves aromatization of ^H adducts through elimination of water by the E1cb mechanism. The reaction products occur in DMSO-d₆ solutions predominantly as 6-methylene-1,6-dihydropyrazines and 5-methylene-4,5-dihydro-1,2,4-triazines.     

Predissociation lifetime of the 1σ g 2 2σ g diabatic state of He 2 + : a one-channel approach

Summary This work is concerned with the application of a one-channel model to obtaining predissociation lifetimes and transition rates in a system of crossing diabatic states. The calculation focuses on the first shape resonance of the 1 _g ² 2 _g diabatic state of He ₂ ⁺ , which is relatively stable with respect to tunneling. This resonance predissociates as a result of the 1 _g ² 2 _g state being crossed by the 1 _g 1 _u ² dissociative diabatic state near the resonance level. We have estimated its predissociation lifetime to be of the order of 10^–11 s.     

Diffusion Conductivity of Electrode Processes under Conditions of Natural Convection

The diffusion conduction = di/d (where i is the current and is the overvoltage) in reversible system [Fe(CN)₆]^3–/4– is measured by the electrochemical impedance method under isothermal and nonisothermal conditions of natural convection. Platinum disk electrodes 3 mm and 20 m in diameter are used. For a macroelectrode under isothermal conditions, passes through a maximum near equilibrium and tends to zero at 0. Under nonisothermal conditions and for a microelectrode under isothermal conditions, achieves a maximum near equilibrium. These data correlate with the dependence of the diffusion layer thickness and quantitatively agree with theory.     

Investigation of h complexes of 2-thienyl phenyl ketones by IR spectroscopy

The shifts of the stretching vibrations of the hydroxyl groups of phenol and pentachlorophenol during the formation of intermolecular hydrogen bonds with 2-thienyl phenyl ketones containing substituents in the benzene ring were measured. A correlation dependence between theD _OH values and ⁺ substituent constants was established.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 482–485, April, 1974.     

Voltamperometry of 1,4-dihydropyridine derivatives

Thirty-nine -substituted 1,4-dihydropyridine derivatives were subjected to electrochemical oxidation on a rotating platinum microelectrode in acetonitrile, and the E_p (E_1/2) values were measured. A satisfactory linear correlation between the E_p and Taft. ^* constants of the substituents in the position was observed. A linear correlation of the E_p values with the ⁰, - and ^– constants also exists.See [1] for communication I.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1525–1529, November. 1975.     

EPR and polarography of nitroazoles. 5. First step in the electrochemical reduction of 2-substituted 5(6)-nitrobenzimidazole using a rotating platinum ring-disk electrode

Using a rotating platinum ring-disk electrode, the electrochemical reduction of 2-substituted 5(6)-nitrobenzimidazoles at the platinum disk in acetonitrile and the oxidation of their radical anions at the ring were studied. During the reduction molecular hydrogen forms by a bimolecular reaction of two primary radical anions. The correlating of electrochemical quantities with the _I, _R, and substituent constants are evidence that E ₁ ^2/d depends on substituent resonance and induction effects to about the same extent, whereas i _lim ^d , n, and E ₁ ^2/r depend predominantly on the resonance effect.For Communication 4, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 827–832, June, 1985.     

A Nonempirical Quantum-Chemical Study and Natural Bond Orbital Analysis of C6H5XCY3 Species (X = SO or SO2, Y = H or F)

The potential functions of internal rotation about the C² _sp—S bonds for C₆H₅XCY₃ species (X = SO or SO₂, Y = H or F) have been obtained at the MP2 (full)/6-31+G(d) level of ab initio theory. It is found that the spatial structures with the plane of C² _sp—S—C³ _sp bonds, which is near perpendicular to the benzene ring plane, are the energy-favourable conformations. The values of the rotational barrier about the C² _sp—S bond are equal to (kJ/mole): 21.2 (C₆H₅SOCH₃), 29.0 (C₆H₅SOCF₃), 20.4 (C₆H₅SO₂CH₃), and 28.2 (C₆H₅SO₂CF₃). On the basis of the Natural Bond Orbital (NBO) analysis results, it has been revealed that the double S=O bond is a strongly polarized covalent -bond, whereas -bond electrons practically are localized on the oxygen atom. The S=O bond order for aromatic sulfoxides and sulphones is mainly caused by hyperconjugational interactions according to the LP(O) ^*(S—C_ipso) and LP(O) ^*(S—C _Y ) mechanisms. In sulphones there is also the additional mechanism of hyperconjugational interactions such as LP(O^{1 *}(S—O²) and LP(O²) ^*(S—O¹). With the replacement of one hydrogen atom on the —XCY₃ group, the charge loss of the unsubstituted benzene molecule increases: —SOCH₃ < —SO₂CH₃ < — SOCF₃ < —SO₂CF₃. The substitution of the —CH₃ group for the —CF₃ group weakly influences the charge value on the sulfur atom but effects the acceptor characteristics of the substituent to a greater extent than the variation of the sulfur atom coordination.     

Spectroscopic study of organosilicon derivatives of thiophene

It is shown that the chemical shifts of hydrogen atoms in the 3 position of the thiophene ring in the PMR spectra of 2-substituted thiophenes are linearly associated with the Hammett _n substituent constants. On the basis of this, it was concluded that silyl substituents in 2-silylthiophenes have electron-acceptor character. It was established that the degree of d–p conjugation between the d orbitals of the silicon atom and the p electrons of the thiophene ring depends on the nature of the other three substituents attached to the silicon atom. The data from the IR spectra of organosilylthiophenes that contain a Si-H bond also attest to the presence of d–p conjugation in these compounds.See [1] for communication I.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 911–915, July, 1972.     

Ionization potentials of halides. Substituent effects in Cl-, Br-, and I-centered radical cations

The first vertical ionization potentials (I) of halides HalX (Hal = Cl, Br, I; X is an inorganic or organic substituent) are linearly related to the inductive (_I), resonance (_R ⁺), and polarizability () constants of the substituents X (I = a + b_I + c_R ⁺ + d). As the atomic number of the Hal element in the Hal^·+X radical cations increases, the inductive interaction is strengthened while the polarizability interaction is weakened. Conjugation remains virtually independent of the Hal atom. The resonance _R ⁺-constants of the MX₃ (M = Si, Ge, Sn, Pb) substituents bound to the Hal^·+ radical cation centers were first calculated.     

Synthesis of mesoionic 3-aryl(hetaryl)-1,2,3,4-oxatriazol-5-ones b based on N-aryl-and N-hetarylhydrazones of bromonitroformaldehyde

Dehydrobromination of N-arylhydrazones of bromonitroformaldehyde (at 20°C) in the presence of alkali and ammonium salts of strong mineral acids, HNO₃, silica gel, and Al₂O₃ forms mesoionic 3-aryl-1,2,3,4-oxatriazol-5-ones (3-arylazasydnones). The effect of the electronic properties of the aryl substituent on the course of the reaction is evaluated. This evaluation is used to develop a general method for preparing 3-arylazasydnones with various substituents including novel 3-hetarylazasydnone derivatives of pyrazole, 1,2,4-triazole and pyridine. Aromatic electronic effects (I, R, m, p) of the mesionic 1,2,3,4-oxatriazol-5-on-3-yl moiety are determined by¹⁹F NMR. A scheme is proposed for the dehydrobromination of the bromonitroformaldehyde N-arylhydrazones that includes the intermediate N-aryl-C-(nitro) nitrilimines, ArN^––N=C⁺NO₂, with subsequent isomerization of the latter into 3-arylazasydnones.N. D. Zelinskii Institute of Organic Chemistry of the Russian Academy of Sciences, Moscow 117913, RussiaTranslated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 413–424, March, 1999.     

CH Acidity of Di- and Trisubstituted Methanes

It is shown that the CH acidity of di- and trisubstituted methanes can be studied using the ap- proaches consisting in singling out the contributions of physically significant factors from the overall acidification mechanisms in the gas phase and in solution. This procedure implies formal decomposition of the calculated gas-phase deprotonation energy Edeprot into the following terms: electrostatic energy of proton detachment from the acid CH bond, with the state of the remainder of the molecule absolutely unperturbed (E ₁); electronic relaxation energy of the resulting molecular residue and formation of a virtual carbanion therefrom (E ₂); the Edeprot component due to displacement of the atomic nuclei on changing from the virtual to real carbanion E ₃. Relationships between the energy components E ₁, E ₂, E ₃, and the commonly used characteristics of the molecular structure were investigated. The parameter E ₁ is selectively sensitive to the inductive effect of the substituent. Imperfect correlation between E ₁ and the sum of the _I constants can be due to the fact that the contributions to the _I constants from the effective charge on the hydrogen atom of the CH bond being deprotonated and from the polarizabilities of the substituents are not taken into account. In contrast to monosubstituted methanes, in di- and trisubstituted methanes there is no correlation between the E ₂ component and the ¹ J(^13CH) constants. The linear dependence linking the sums of the components E ₁ + E ₂ and the pyramidal angle in the carbanions is responsible for the relaxation nature of the effects associated with the E ₂ + E ₃ sum. Comparison of the data obtained with the calculated patterns of redistribution of the effective charges on atoms accompanying conversion of CH acids to carbanions enabled elucidation of the relative contribution of each of the components, E ₂ and E ₃, to the deprotonation energy of selected groups of substituted methanes. The previously developed technique of separating the energy of protolytic equilibrium in the gas from that of solvation processes in solution enabled assessment of the contributions from electrostatic solvation to pK _a in DMSO. The same technique of singling out the solvation component due to intermolecular hydrogen bonds from pK _a(H₂O) was used in studying the acid-base equilibria for substituted methanes in aqueous solution. It was shown that the solvation effects manifested in the liquid-phase CH acidity can be modeled by the effects revealed for analogous hydrogen bonds of ion-molecule complexes in the gas phase. The relationships between the strength of hydrogen bonds and the CH-acidic properties of compounds in the gas phase and liquid water are similar.     

Exponential temperature change in thermal analysis at non-isothermal kinetics

The applying of exponential temperature programming: dT/dt=T orT=T ₀ e ^t in thermal analysis at non-isothermal kinetics is discussed. An approach for the integration of the temperature integral is presented.     

Interpretation of AC Conductivity of Lightly Doped Conducting Polymers in Terms of Hopping Conduction

The ac conduction of most disordered materials shows a regime of constant dc conductivity (0) at low frequencies and a crossover to a frequency-dependent regime of the type A ^s at high frequencies. We discuss the physical origin of this behavior and the interpretation of the onset frequency of excess ac conduction, _c , in terms of models for hopping conduction of polaronic carriers in a disordered medium. We emphasize the central role of the critical hopping rate in the percolation lattice for determining both (0) and _c . We show the behavior of () for lightly doped polypyrrole samples at different stages of doping, and we discuss the significance of frequency dispersion effects for electrochemical measurements.     

Substituent parameters for radical reactions Cerium(IV) — substituted toluenes — acrylonitrile system

Summary In the present study, a new approach for the determination of ', that is, radical substituent parameter, has been described. The technique is based on two equations, one reported byYamamoto andOtsu and the other byStreitwieser andPerrin. The system used for the determination of the radical substituent parameter (') was Ce(IV) — substituted toluenes — acrylonitrile system. To explain inhibition, it has been suggested that the reaction scheme involves initiation of polymerization by Ce(IV) and termination by primary radical of the substrate. The kinetic expression based on the reaction scheme formulated could explain the unusual observation of a negative intercept found in the plot of [M]/R _p versus 1/[M]. Whereas a plot of log /₀ against ⁺ did not give a straight line, a good linear plot with zero intercept was obtained when log /₀ was plotted against (⁺ + '). This proves the validity of ' values which have been determinded.     

Relation between the Length of the Transannular Bond Si←N in 1-Substituted Silatranes and the Inductive Effect of Substituents at the Silicon Atom

A strict linear correlation is found between the length of the coordination bond Si-N in 1-substituted silatranes XCH₂Si(OCH₂CH₂)₃N and the inductive constant _I of substituent XCH₂. This equation is also valid for other compounds of the RSi(OCH₂CH₂)₃N type, in which silicon is bound to an sp ²-carbon atom (R = CH = CH₂, Ph, 2-furyl, 2-thienyl, etc.). The deduced correlation equation allows determination of earlier unknown and refinement of existing _4I constants of substituents R on the basis of X-ray diffraction Si-N bond lengths in silatranes RSi(OCH₂CH₂)₃N. Deviations from the correlation point to noninductive interaction between substituent R and the silantranyl group (R = R'O). The bond length in 1-fluorosilatrane nicely fits the deduced equation.     

Excited Π states of divinyl chalcogenides and chalcophenes

Electron transitions in divinyl chalcogenides (CH₂=CHXCH=CH₂, where X is S, Se, or Te) have been analyzed using UV absorption spectra of dialkyl and alkyl vinyl chalcogenides. The following relations for the orbital energies are found: ^* < ^* < ^* < ^* for Te and ^* < ^* < ^* < ^* for S and Se. For chalcophenes, a correlation between the energy of the excited state (E ^*) of specific symmetry, the ionization potential (I) and the electron affinity (EA) is obtained:E ^*=const+(I+EA)/2. The electron affinity of divinyl chalcogenides is estimated. The correlation between the excited ^* states of divinyl chalcogenides and chalcophenes is discussed.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 831–835, May, 1994.     

Mercuration of σ-cymantrenyl-(π-cyclopentadienyl)dicarbonyliron

Conclusions We were able to mercurate-cymantrenyl-(-cyclopentadienyl)dicarbonyliron in the cyclopentadienyl ring of the cymantrenyl group to give C₅H₅(CO)₂FeC₅H₃(HgCl)Mn(CO)₃ and [C₅H₅(CO)₂FeC₅H₃Mn(CO)₃]₂Hg.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 6, pp. 1438–1439, June, 1978.