Investigation of the electronic effect of the diphenylphosphino group

We have synthesized meta-substituted derivatives of benzoic acid, determined their ionization constants in water-alcohol solutions of concentration 11 and 14 by volume, and calculated the Hammett constant _m of the diphenylphosphino (0.12), diphenylamino (–0.04), diphenylphosphinyl (0.40) and diphenylthiophosphinyl (0.32) groups. Unlike the diphenylamine group, the diphenylphosphino group is metaorienting, which is probably to be explained by the absence or the weak nature of p- conjugation of incomplete electron pairs on the phosphorus and the presence of an electron-acceptor effect (d-p conjugation).     

Quasi-homeopolar states in conjugated hydrocarbons. Interaction of π- and σ-electrons

Quasi-homeopolar levels of - and -electrons in conjugate hydrocarbons are considered. It is shown that in the spin hamiltonian and the projected operators of the physical values there appear terms which involve --interaction. The spin hamiltonian of --interaction is small, and its contribution to energies and spin functions can be calculated from perturbation theory by taking the spin hamiltonian of noninteracting - and -electrons as equal to zero. The - and -electrons of the C=C bond in ethylene are considered in detail. Calculations show that their interaction increases the excitation energy of the lower triplet of ethylene. The spin hamiltonian parameters of the simplest conjugate hydrocarbons are determined.The accuracy of the valence-bond method is investigated on the basis of the theory of quasi-homeopolar levels. It is shown that empirical selection of the parameters partially compensates for the errors which are made in the derivation of the fundamental equation for this approximation.     

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).     

Relationships between the lengths,orders, hybridization of the atoms,and force constants of carbon—nitrogen and carbon—oxygen bonds

The bond order—bond length, bond length—average percentage s-character, and bond order—bond -shortening relationships have been obtained for CN and CO bonds. It has been shown that the differences in bond lengths are due chiefly to the specific features of the -bonds. The observed relationship between the length of the -bond and the average percentage s-character is linear. It has been noted that the bond lengths are most sensitive to the -order when it changes in the range 0.3–1.0. For CC, CN, and CO bonds, relationships have been obtained between the -order and the force constants, and for the single bonds the relationship between the average percentage s-character and the force constants has been obtained.     

Study of the effects of conjugation in alkenyl derivatives of silicon and germanium by infrared spectroscopy

Conclusions The effects of d-p and, conjugation in the vinyl and allyl derivatives of silicon and germanium depend on the nature of the other three substituents.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 9, pp. 2074–2076, September, 1971.     

Substituent Effects on the Driving Force for Inclusion Complexation of α- and β-Cyclodextrin with Monosubstituted Benzene Derivatives

The association constant values, K_a, for the inclusion of - and -CD with monosubstituted benzene derivatives were determined by means of UV-vis and fluorescence spectroscopy. The stability of the complexes is influenced by the properties of the substituents of the guest compounds. Regression analysis was used to create a set of inclusion models with the experimental association constant ln K_a and the corresponding substituent molar refraction R_m, hydrophobic constant and Hammett constant of the benzene derivatives. The ln K_a value mainly correlated with R_m for -CD and with both R_m and for -CD complexes. The association constants predicted by the models are in good agreement with the experimentally determined data. This suggests that the inclusion complexation of benzene derivatives with -CD is predominantly driven by van der Waals force and with -CD mainly by van der Waals force and hydrophobic interactions.     

The electronic structures of some tetrazaborolines and dimethyltetrazadieneirontricarbonyl

Self-consistent field calculations have been performed on some ² tetrazaborolines using both an ab initio and a semi-empirical (CNDO) approach. The first method was employed in order to examine completely the ground-state and the properties of the -electrons in the parent molecule. The excited states of several boron-substituted derivatives of tetrazaboroline have also been calculated semi-empirically, including configuration interaction, and good agreement with the observed electronic absorption spectra was obtained. The results of the calculations were also invoked to distinguish between isomeric boron-substituted derivatives of tetrazaborolines. The electronic structures of two of the possible geometries of dimethyltetrazadieneirontricarbonyl, in which the N₄ moiety is attached in a or a fashion were examined by CNDO calculations and it was found that the more stable form involves bonding between the nitrogens and the iron atom.

---

Zusammenfassung Für einige ²-tetrazaborwasserstoff-Derivate wurden SCF-Rechnungen nach einem ab initio- und nach einem semiempirischen (CNDO)-Verfahren durchgeführt. Die erste Methode wurde angewandt, um den Grundzustand und die Eigenschaften der -Elektronen im Ausgangsmolekül zu untersuchen. Die angeregten Zustände einiger am Boratom substituierter Derivate wurden semiempirisch unter Einschluß von Konfigurationenwechselwirkung berechnet, wobei gute Übereinstimmung mit den experimentellen Elektronenspektren erzielt wurde. Die Resultate wurden ebenfalls zur Unterscheidung verschiedener isomerer Derivate benutzt. Die Elektronenstruktur von zwei möglichen Geometrien des Dimethyltetrazadieneisentricarbonyl, in denen der N₄-Rest mit einer -oder -Bindung gebunden ist, wurde mit CNDO-Rechnungen untersucht. Es wurde gefunden, daß die stabilere Form -Bindungen zwischen den Stickstoffatomen und dem Eisenatom enthält.

     

Kinetics and mechanism of KBrO3 oxidation of D(+) xylose in acidic medium

KBr₃ oxidation of xylose, in presence of H₂SO₄, follows first order kinetics in [KBrO₃] and [xylose], and second order in [H₂SO₄]. The acid-catalyzed reaction gives aldonic acid as product. A mechanism consistent with temperature, solvent, higher acidity and salt effects has been proposed. Thermodynamic constants have been calculated.

---

KBrO₃ H₂SO₄ [KBrO₃] [] [H₂SO₄]. - . , , , . .

     

The electronic spectrum of acrylonitrile

The vapor absorption spectrum of acrylonitrile CH₂CHCN has been measured in the vacuum ultraviolet region. In addition, an all-valence-electron molecular orbital calculation has been used to calculate the electronic structure and spectrum of the molecule. On the basis of the MO calculation, as well as a vibrational analysis of the observed spectrum, several electronic transitions are assigned. The lowest energy absorption band (2107Å, = 150) is assigned as an n ^* transition. Absorption bands at 2030Å (=1600), 1725Å ( = 2100), and 1570Å ( = 1920) are assigned as 0–0 bands associated with transitions that are, respectively, ^*,^*, and ^* in character.

---

Zusammenfassung Das UV-Absorptionsspektrum von dampfförmigen Acrylnitril wurde gemessen und eine CNDO/2-Rechnung für die Elektronenstruktur durchgeführt. Auf dieser Basis konnten unter Zuhilfenahme der Analyse der Schwingungsstruktur im beobachteten Spektrum mehrere Banden zugeordnet werden: die 2107-Å-Bande ( = 150) einem n^*-Übergang, die drei Banden bei 2030Å ( = 1600), 1725Å ( = 2100) und 1570 Å ( = 1920)0-0-Übergängen von ^*-, ^*- bzw. ^*-Banden.

---

Résumé Mesure du spectre d'absorption en phase vapeur de l'acrilonitrile CH₂CHCN dans la région de l'ultraviolet. Par ailleurs, la structure électronique et le spectre de la molécule ont été calculés à l'aide d'une méthode des orbitales moléculaires semi-empirique pour tous les électrons de valence. Sur cette base, ainsi que sur une analyse vibrationnelle du spectre expérimental, on procède à l'attribution de plusieurs transitions électroniques. La bande d'absorption de plus basse énergie (2107 Å, = 150) est attribuée à une transition n ^*. Les bandes d'absorption à 2030Å ( = 1600), 1275Å ( = 2100) et 1570Å ( = 1920) sont considérées comme des bandes 0 - 0 associées à des transitions ^*, ^* et ^* respectivement.

     

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.     

Study of the thermal decomposition processes of clathrate compounds

The decompositions of the clathrate compounds [M(NCS)₂(4-MePy)₄]·nG (whereM=Mn, Co, Ni or Cd;G=4-methylpyridine (4-MePy), benzene or xylenes) were studied on a Q-derivatograph under quasi-equilibrium conditions and with linear heating. These clathrates can be divided into two groups, in which the loss of guest is either (I) accompanied by destruction of the host complex, or (II) occurs before decomposition of the host complex. Kinetic parameters were obtained.

---

Zusammenfassung Die Zersetzung von Clathrat-Verbindungen der Zusammensetzung [M(NCS)₂(4-MePy)₄]·nG (M=Mn, Co, Ni, Cd;G=4-Methylpyridin (4-MePy), Benzen, o-,m, p-Xylen) wurde mittels Q-Derivatograph unter Quasi-Gleichgewichtsbedingungen und bei linearer Aufheizung untersucht.Die studierten Clathrate lassen sich in zwei Gruppen einteilen, je nachdem ob die Abgabe des Gastmoleküls G entweder vor oder unter Gleichzeitiger Zerstörung des Wirtskomplexes erfolgt. Kinetische Parameter wurden ermittelt.

---

Q- [M(NCS)₂(4-MePy)₂]·nG, M , , , G — 4- , . , . .

     

Ba(OH)2 as catalyst in organic reactions: I. Nature of active sites in the michael addition

In order to determine the nature of active sites that act in the Michael addition of ethyl malonate to chalcone in EtOH, catalyzed by activated barium hydroxide, selective poisoning experiments have been carried out. It has been found that the catalytic activity of the C-200 catalyst is related to the strong basic sites titrated by TBMPHE.

---

, - . , C-200 - , TBMPHE.

     

Ab initio SCF and CI study of the electronic spectrum of pyridine N-oxide

Configuration interaction (CI) studies of ground, n *, * * electronically excited states are reported for pyridine N-oxide. The transition energy to the lowest * excited ¹ B ₂ state is calculated at 4.35 eV, compared to the experimental spectrum range of 3.67–4.0 eV. This state lies below the lowest n * excited ¹ A ₂ state calculated at 4.81 eV above the ground state. The only experimentally reported triplet state at 2.92 eV above the ground state is predicted to be the ³ A ₁ (*) state. The calculated energy lies at 3.27 eV. Numerous other high-lying singlet states as well as the triplet states have also been calculated. The intramolecular charge transfer character of the ground and the excited states have been studied in terms of the calculated dipole moment and other physical properties.     

Diatomic interactions in momentum space. The 2pπ u and 3dπ g states of H 2 + system

The recently proposed method of momentum electron density for interatomic interactions is applied to the two states of the H ₂ ⁺ system. The processes of the attractive 2P _u and repulsive 3d _g interactions are analysed based on the behaviour of the momentum density and Compton profile. The results are compared with the previous ones for the 1 _{S g} and 2p _u states. The guiding principle of contraction and expansion for the energy-density relation in momentum space is shown to be common to both the and states.     

Quantum-chemical study of allylic compounds with two bonded heavy atoms

It has been shown by the CNDO method that the bathochromic shift of the long-wave absorption band in the transition from allylstannane to compounds of the type C=C-C-Sn-X and C=C-Sn-X (where X is a heavy atom) is connected with the formation of a low-energy vacant *_S-X orbital, localized mainly in the region of the Sn-X chemical bond, and of an occupied _Sn-X orbital, the energy of which is somewhat higher than of the _C-Sn orbital. The dependence of the position of the long-wave absorbance region on conformation is related to the fact that, in planar and nonplanar conformers, the long-wave transitions are of a different type ( * and *, respectively); the bathochromic shift is determined to a large degree by the difference in the energies of the highest occupied MO ( - ) in the s-trans form. In the nonplanar conformers the heavy atom orbitals interact with the -orbital of the ethylene moiety through the bridge group; this leads to a significant delocalization of the HOMO and to a considerable change in its energy. On the other hand, their interaction with the *-orbital in compounds of the C=C-C-Sn-X type is very low and does not favor the delocalization of lower vacant MO. In vinyldistannane the *-orbital is noticeably delocalized, due to the interaction with the *_Sn-Sn orbital in planar and with the *_Sn-Sn orbital in nonplanar conformers.N. D. Zelinskii Institute of Organic Chemistry, Russian Academy of Sciences, 117913 Moscow. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 3, pp. 636–641, March, 1992.     

Configuration mixing involving σ and π orbitals

The effect (on the energy of the different states) of including doubly excited configurations in a - plus -configuration interaction treatment, is studied within the CNDO/2 framework. For moderately large molecules the problem of the choice of the type ( or ) of configurations taken into account is examined. When possible, comparison is made with similar non empirical calculations.

---

Zusammenfassung Im Rahmen der CNDO/2 Methode wird der Einfluß (auf die Energien verschiedener Zustände) des Einschlusses doppelt angeregter Konfigurationen in einer - und -Konfigurationswechsel-wirkungs-Behandlung studiert. Für nicht allzu große Moleküle wird das Problem der Wahl der Art ( oder ) der berücksichtigten Konfigurationen untersucht. Soweit möglich, werden die Resultate mit denen ähnlicher nichtempirischer Rechnungen verglichen.

---

Résumé L'effet (sur l'énergie des différents états) de l'introduction de configurations diexcitées dans une interaction de configuration plus , est étudié dans le cadre de la méthode CNDO/2. Pour des molécules de taille moyenne le problème du choix du type ou des configurations est examiné. Les résultats obtenus sont comparés aux calculs non-empirique similaires disponibles.

     

Origin of the conical intersection between the singlet ionic excited surfaces of twisted ethylene

The potential surfaces of the two valence ionic singlet excited states of twisted ethylene are known to exhibit a conical intersection for a twist angle of the double bond near 82°, and no pyramidalization of the CH₂ groups. The factors responsible for the stabilization of the symmetric excited state near 90° are shown to be ( )² and ( ^*)² double excitations. The analysis is performed in the Quasi Degenerate Perturbation Theory formalism. The analogy with the ¹ A _g ³ B _u ordering problem of the diradical ground and lower triplet states through a double spin polarization of the system is established.     

Elektronenstruktur und Spektren von Phenylcycloheptatrienylium-Kationen

Zusammenfassung Die Elektronenstruktur von Phenylcycloheptatrienylium-Kationen wurde mit Hilfe von Einelektronen-LCAO-MO-Methoden (HMO- und EHM-Methode) untersucht. In den verdrehten Strukturen der Kationen tritt starke –-Wechselwirkung von einem Ring zum anderen hin auf. Die Rechenresultate werden mit den UV- und NMR-Spektren von 15 zum Teil neu dargestellten Kationen verglichen. Die NMR-Spektren von Phenylcycloheptatrienyliumionen mit und ohne Substituenten in den Stellungen 1 oder 1 unterscheiden sich signifikant voneinander. Diese Unterschiede können durch die verschiedenen Ladungsdichten an den einzelnen Wasserstoffatomen erklärt werden. Für die Kationen ohne Substituenten in den Stellungen 1 oder 1 wird ein dihedraler Winkel <45° wahrscheinlich gemacht.

---

Electronic structure and spectra of phenyl-cycloheptatrienyl cations

The electron structures of phenylcycloheptatrienylium cations have been studied using one-electron LCAO-MO-methods (HMO- and EHM-method) and strong –-interaction was observed between twisted rings. The calculated results were compared with UV and NMR spectra of 15 cations synthesized in part for the first time. The NMR spectra of phenylcycloheptatrienylium cations with and without substituents in positions 1 and 1 were found to differ significantly. The differences can be accounted for assuming differently charged hydrogen atoms. A dihedral angle of <45° probably can be assumed for cations without substituents in positions 1 or 1.

---

---

Mit 9 Abbildungen     

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.

---

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.

---

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.

---

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

     

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.