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.     

Electronic effects of 1-(1, 7-B6H6C2H) and 1-(1,6-B7H7C2H) groups

Conclusions 1-[1,7-Dicarbaclozooctaboran(8)yl] (induction constant _i=0.08 and resonance constant _R°=–0.02) and 1-[1,6-dicarbaclozononaboran(9)yl] (=0.09 and _R°=0.05) groups are weak electron-acceptor groupings.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 3, pp. 574–576, March, 1972.     

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.     

Electronic effect of the 1-[η5-cyclgpentadienyl-η5-(3)-1,2-dicarbollyliron(II)] group

Conclusions The Taft method was used to determine the electronic effect of the 1-[⁵-cyclopenta-dienyl-⁵-(3)-1,2-dicarbollyliron(II) ] group which displays strong electron-donor properties: _I=–0.22 and _R=–0.20.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 6, pp. 1449–1451, June, 1985.     

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.     

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.     

Quasi-tautomerism of 5-hydroxy-5-phenyl-5H-pyrido[2,3-b]chromenes in sulfuric acid

The existence of a quasi-tautomeric equilibrium in solutions of 5-hydroxy-5-phenyl-5H-pyrido[2,3-b]chromenes in sulfuric acid, which was confirmed by a linear dependence of the logarithms of the indicator ratios on acidity function H_R — H_O with a slope close to unity, was established. The pK values of this equilibrium correlate with the _p ^o and _R. ^o substituent constants.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 753–755, June, 1984.     

Synthesis and acid-base transformations of 8-substituted 10-phenyl-10-hydroxy-10H- pyrido [2,3-b ]chromenes

The corresponding 2-(p-substituted phenoxy)-3-aroylpyridines were obtained by the reaction of 2-(p-substituted phenoxy)nicotinonitriles with phenylmagnesium bromide. It is shown that they are readily cyclized to 8-substituted 10-phenyl-10-hydroxy-10H-pyrido[2,3-b]chromenes by the action of concentrated sulfuric acid in glacial acetic acid. The pK_R+ values of the cyclization products, which range from–7.70 to –10.83 and correlate with the _p ⁰ substituent constants, were determined by spectrophotometry.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 614–616, May, 1982.     

Hammett-Taft constants of substituted 2- and 4-quinazolinyl groups

From the chemical shifts of the meta- and para-carbon atoms of the phenyl group in phenylquinazolines the _I and _R ⁰ constants of 2- and 4-quinazolinyl groups were determined. Correlation equations which enable us to calculate the constants of various substituted 2- and 4-quinazolinyl groups are proposed.Deceased.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 3, pp. 686–690, March, 1991.     

Charge control in the formation of complexes of phenol with unsaturated compounds containing organometallic substituents from group IV

The resonance donor effect of the , conjugation of R₃M and R₃MCH₂ (M = Si, Ge, Sn; R is an alklyl group) substituents with the triple bond in compounds R₃MC=CX and R₃MCH₂CCX (X = H, R) changes on passing from isolated molecules to their H-complexes. A partial ⁺ charge on the triple bond enhances , conjugation; a partial ^– charge on the triple bond has practically no effect on the resonance properties of R₃M substituents, whereas the , conjugation of R₃MCH₂ substituents diminishes owing to the effect of negative direct resonance interaction. The effect of , conjugation on the effective negative charges of the carbon atoms in the -CC- fragments was estimated quantitatively.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1041–1046, June, 1994.This work was supported by the Russian Fundation for Basic Research (Grant 93-03-18372).     

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.     

Determination of reactivity constants of 5-substituted 2-indolyl groups by means of13C NMR

Conclusions A series of 5-substituted 2-phenylindoles has been synthesized; the¹³C chemical shifts have been measured for these compounds in acetone, and these data have been used to determine the _I and _R ^O constants of the 5-substituted 2-indolyl groups. Relationships have been found for the estimation of the constants of any 5-substituted 2-indolyl group.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 312–315, February, 1985.     

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.

     

19F NMR study of the electronic effect of the tropylium cation

Conclusions The electronic effect of the tropylium cation as a substituent in the benzene ring was found according to the Taft method. In its inductive effect (_I=+0.54), the tropylium cation is a strong electron-withdrawing group, while its electron-withdrawing resonance effect (_r ⁰=+0.13) is relatively slight. In its overall electronic effect, the tropylium cation is similar as a substituent to the perfluoroethyl group.Translated from Izvestiya Akaderaii Nauk SSSR, Seriya Khinicheskaya, No. 6, pp. 1434–1436, June, 1988.     

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.     

Electronic effects of the 1-[CLOSO-3,3,3-(CO)3-3,1,2-ReCaB9H10]− and 1-[CLOSO-3,3,3-(CO)3-3,1,2-.MnC2B9H10]- groups

Conclusions The electronic effects of the 1-[closo-3,3,3-(CO)₃-3,1,2-ReC₂B₉H₁₀]^– (_I=-0.066; _r ^o=0.101) and 1-[closo-3,3,3-(CO)₃-3,1,2-MnC₂B₉H₁₀]^–(_I=0.090; _r ^o=0.165) groups were determined by the Taft method.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, pp. 2296–2298, October, 1987.     

Spectroscopic study of compounds possessing a bond of an element of group IVB with hydrogen

Conclusions The frequencies of the valence vibrations of the Si-H bond in trisubstituted silanes depends not only on the inductive effect of substituents, but also on the effects of d-p interaction, ,- and p,-conjugation. An analysis was made of the relative contributions of these effects, depending on the nature of the substituent.For the preceding communications, see [1, 2].Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 3, pp. 544–550, March, 1971.     

Correlation of nucleae quadrupole resonance frequencies with some chemical constants in the aliphatic series

Linear relationships are established between the nuclear quadrupole resonance frequencies of alkyl chlorides, RCl, on the one hand, and the pK_a values of RCOOH and RNH₂ as well as the Taft ^* constants, on the other hand. Similar linear correlations were found between the NQR frequencies of the substituted compounds XCH₂Cl and the pK_a of XCH₂COOH, XCH₂NH₂, XCH₂OH, as well as the ^* constants of XCH₂ radicals, where X are electronegative substituents. X substituents with unshared electron pairs (RO, RS, F, Cl, Br) are an exception; nevertheless, the deviation of these points is regular and depends linearly on the resonance parameters _R ⁰ or _R of the X substituents. The relationships can be used for an approximation of the ionization constants of a number of fatty acids, for the calculation of the Taft ^* constants of radicals R and XCH₂ and of the resonance parameters _R ⁰ and _R of X substituents with an accuracy which in many cases is in no way inferior to that of the experimental values, and also for the approximate evaluation of the ionization constants of XCH₂NH₂ amines and XCH₂OH alcohols.     

On the importance of scale and polarization of the atomic orbital basis for LCAO calculations of electronic intensities

The importance of scale and polarization of the atomic basis set for LCAO calculations of the intensities of electronic transitions is investigated using the molecular hydrogen ion, H ₂ ⁺ , as a model. The transitions under consideration are the 1 _g–1 _u the 1 _u–1 _g and the 1 _g–1_uit excitations of this ion, and the electric dipole transition moments are calculated for a range of nuclear separations using the dipole length, the dipole velocity, the dipole acceleration and the time-derivative of the dipole acceleration formulations. For the 1 _g–1 _u and the 1 _u–1 _g excitations scaling and/or polarization are found very efficient for the improvement of the calculated transition moments for small internuclear separations for all the dipole formulations, whereas only the dipole length and the dipole velocity results are well-behaved for large separations. For the 1 _g–1 _u excitation scaling is found to be more important than polarization for all internuclear separations.

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Zusammenfassung Die Bedeutung der Skalierung und der Polarisation atomarer Basisfunktionen für LCAO-Berechnungen der Intensitäten elektronischer Übergänge wird am Wasserstoffmolekülion, H ₂ ⁺ , als Modell untersucht. Die betrachteten Übergänge sind der 1 _g–1 _u der 1 _u–1 _g und der 1 _g –;1 _u-Übergang dieses Ions. Die zugehörigen Dipolübergangsmomente werden für eine Reihe von Kernabständen berechnet, wobei die Dipollänge, die Dipolgeschwindigkeit, die Dipolbeschleunigung und die zeitliche Ableitung der Dipolbeschleunigung zu Grunde gelegt werden. Für die 1 _g–1 _u und die 1 _u–1 _g-Anregung findet man, daß Skalierung und/oder Polarisation sehr wirksam für eine Verbesserung der berechneten Übergangsmomente bei kleinen Kernabständen sind. Dies gilt für alle Dipolformulierungen, während sich für große Kernabstände nur die Dipollänge und die Dipolgeschwindigkeit richtig verhalten. Für den 1 _g–1 _u-Übergang ist die Skalierung bei allen Kernabständen wichtiger als die Polarisation.

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Résumé Etude de l'influence de l'échelle et de la polarisation de la base atomique sur les calculs LCAO des intensités des transitions électroniques, en utilisant l'ion moléculaire H ₂ ⁺ comme modèle. On considère les transitions 1 _g–1 _u,1 _u–1 _get 1 _g–1 _u; les moments dipolaires de transition sont calculés pour un éventail de séparations nucléaires en utilisant les différentes formulations: longueur dipolaire, vitesse dipolaire, accélération dipolaire et dérivée par rapport au temps de l'accélération dipolaire. Pour les excitations 1 _g–1 _u-et 1 _u–1 _gles facteurs précités ont une grande importance pour l'amélioration des moments de transition calculés à faible séparation nucléaire dans toutes les formulations, alors qu'à grande séparation nucléaire seules la longueur et la vitesse donnent des résultats convenables. Pour l'excitation 1 _g–1 _ul'échelle est un facteur plus important que la polarisation à toutes distances internucléaires.

     

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.