Application of the generalized principle of maximum overlap to the study of the stereochemistry of β-elimination reactions

The dependence of the degree of charge transfer in substituted alkanes on the relative positions and electron-donor (or acceptor) properties of the groups eliminated in -elimination reactions has been studied. Rules obtained from the generalized principle of maximum overlap have been used for the analysis of the relations between the coefficients in front of the basis functions in the expansions of the MOs. It has been established that trans elimination is observed in the case of substituents with pronounced electron-acceptor and electron-donor properties. In heterogeneous-catalytic reactions the nature of the active sites on the surface of the catalyst strongly influences the electron-donor (or acceptor) properties of the groups being eliminated. The catalytic dehydrochlorination of 1,1,2-trichloroethane has been considered as an example.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 22, No. 2, pp. 168–174, March–April, 1986.     

Theoretical analysis of counterfoil influence over the physicochemical properties of aniline tetramers in several oxidation states

We present semiempirical quantum chemical calculations of geometric structures, charge distributions, energy levels, ionization potentials, and enthalpies of formation for aniline tetramers in different oxidation states using the semiempirical AM1 method. For tetraaniline radical cation the effect of these three counterions on the above-mentioned physicochemical parameters was analyzed. The ions studied included Cl^–, HSQ₄ ^–, and CH₃COO^–. Chloride counterion showed a large charge transfer to the chain, as was shown in a preceding work [4]. HSO₄ ^– showed a strong charge stabilization without transfer. CH₃COO^– exhibits hydrogen bond formation and also displays a strong charge stabilization in a fragment of the chain, but does not transfer any charge. Also, Cl^– was able to form a hydrogen bond, depending on the initial position that it occupies in relation to the tetrameric chain, which is then optimized. Charge transfer is present for the Cl^– cases. For dication structures the effect of SO ₄ ^2– was analyzed. Our calculations showed that the distribution of the energy levels of tetraaniline radical cation can be comparable to the polyaniline ones by adding a counterion to the tetramer.     

给、吸电子基团对吡嗪衍生物电子结构影响的DFT研究

采用B3LYP方法在6—31G^#基组水平上优化了对位取代吡嗪衍生物的几何构型，利用TD—DFT方法计算了它们的前线分子轨道能级和电子光谱．结果表明，带有给、吸电子基团对吡嗪衍生物与苯、吡啶相比，也具有很好的共轭性；随着分子共轭链的增长，分子的偶极矩增大，前线分子轨道能级差减小，最大吸收波长发生红移．对于具有相同共轭链的同分异构体，推电子基团与具有给电子性质的共轭链相连，则分子的电荷转移明显，导致偶极矩增大，前线分子轨道能级间的电子跃迁更容易；吸电子基团与具有给电子性质的共轭链相连，情况正好相反，这些结果对分子设计有重要意义。     

Influence of chloromethyl substituent on structure and donor-acceptor properties of 10-methyl-10-chloromethylphenothiasiline

Summary From an x-ray structure study of crystals of 10-methyl-10-chloromethylphenothiasiline, it has been found that the presence of the electron-acceptor substituent CH₂Cl on the Si atom leads to destabilization of the heterocycle, an increase in nonplanarity of the molecule, and a weakening of its aromatic properties, both in the ground state and in the state with charge transfer.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2436–2441, November, 1981.The authors wish to thank V. F. Traven' for furnishing the crystals, and A. G. Kozlovskaya for participating in the work.     

Synthesis of sterically hindered aromatic aldehydes

Formylation of mesitylene, durene, and m-xylene derivatives containing electron-donor and electron-acceptor substituents by dichloromethyl methyl ether was studied in the presence of TiCl₄. A series of functionally substituted sterically hindered benzaldehydes was prepared from the products of these reactions.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1609–1615, July, 1991.     

Polarographic oxidation of triarylimidazoles

Ten series of triarylimidazoles were subjected to polarographic oxidation. It was found that electron-donor substituents facilitate polarographic oxidation, while electron-acceptor substituents hinder it. Correlation equations in coordinates of E_1/2 and ⁺ were found for all of the investigated series.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 387–390, March, 1973.The synthesis and characteristics of the investigated imidazoles were described in [7–10].     

Gas chromatography–mass spectrometric identification of iodine species arising from photo-chemical vapor generation

Ultraviolet irradiation of aqueous solutions of iodide/iodate ion containing low molecular weight organic acids generates volatile iodine species that are amenable to detection by atomic spectrometry. In the presence of formic, acetic or propionic acids, photo-chemical generation results in the formation of HI, methyl- and ethyl-iodide respectively, the latter two products being directly identified by gas chromatography–mass spectrometry. Deuterium and ¹³C-labeled reagents were employed to elucidate the provenance of the alkyl group. Use of ¹³CH₃–COOH produced ¹³CH₃–I; deuterated acetic acid (D₃C-COOD) resulted in the formation of CD₃–I. These observations indicate direct transfer of the alkyl group from the carboxylic acid to iodide, consistent with the suggestion that the mechanism of synthesis involves radical induced reactions.     

Charge-transfer complexes of chloranil with trialkylsilylmethyl esters of α-phenylbutyric and N-substituted aminoacetic acids

Conclusions ELectronic spectral data for charge-transfer complexes of choranil with trialkylsilyl-methyl esters of -phenylbutyric and N-substituted aminoacetic acids indicate that the CH₂CO₂CH₂SiAlk₃ group has an electron-donor effect, leading to an increase in electron density of the aromatic ring and arylamino group.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1670–1671, July, 1986.     

Quantum Chemical Calculation of Conformations and Rotation Barriers of Functional Groups in Arylsulfonyl Halides

The semiempirical PM3 method is used to calculate the potential functions of internal rotation of the functional groups –SO₂Cl, –NO₂, –CH₃, –OCH₃, and –NH₂ of benzenesulfonyl halide molecules (PhSO₂Hal, Hal = F, Cl, Br, I) and twelve substituted derivatives of benzenesulfonyl chloride. Molecular conformations have been determined and internal rotation barriers of the functional groups have been calculated. For meta- and para-substituted benzenesulfonyl chlorides, the projection of the S–Hal bond is perpendicular to the plane of the benzene ring. The rotation barriers of the –SO₂Hal group of benzenesulfonyl halides increase in the series Hal = F, Cl, Br, I. The rotation barriers of the –SO₂Cl group of benzenesulfonyl chloride with meta- and para-substituents slightly increase with the electron-donor properties of the substituent. The rotation barriers of the functional groups of ortho-substituted benzenesulfonyl chlorides are 3 or 4 times as high as those of the meta- and para-isomers. For para-substituted benzenesulfonyl chlorides, the rotation barriers of the functional groups increase in the order –CH₃, –NO₂, –SO₂Cl, –OCH₃, –NH₂.     

The interaction of water with sulfonium ions and the effects of hydration on the energetics of methyl group transfer: An ab initio molecular orbital study of the hydration of (CH3)3S+ and (CH3)2S+CH2CO2 −

The interactions of the sulfonium ions (CH₃)₃S⁺, (CH₃)₂S⁺CH₂CO₂ ^–, and (CH₃)₂S⁺-CH₂CH₂CO₂ ^– with up to four water molecules have been studied by ab initio molecular orbital methods. Complexes of (CH₃)₃S⁺ with one to three water molecules involve strong electrostatic sulfur-oxygen interactions; in contrast, the sulfide (CH₃)₂S interacts with water molecules via weak S-H hydrogen bonds, suggesting that methyl-group transfer from (CH₃)₃S⁺ in aqueous solution involves a significant alteration of the hydration pattern around the sulfur atom. Two conformers of (CH₃)₂S⁺CH₂CO₂ ^– were found that display sulfur-oxygen distances which are approximately 0.3 å less than the sum of the sulfur and oxygen van der Waals radii, indicating a strong intramolecular electrostatic interaction. For the complexes (CH₃)₂S⁺CH₂CO₂ ^–·nH₂O(n =1–4), water interacts primarily with the carboxylate group via hydrogen bonds, rather than electrostatically with the sulfur atom, although in complexes with the three- and four-water complexes, the proximity of the positively charged sulfur atom to the carboxylate group significantly alters the hydration pattern compared to that in the corresponding of complexes CH₃SCH₂CO₂ ^–· Thus, methyl transfer from (CH₃)₂S⁺CH₂CO₂ ^– to an acceptor in aqueous solution also involves substantial changes in the hydration pattern around the carboxylate group.     

Kinetics and mechanism of the addition of the phthalimid-n-oxyl radical to the double bond of vinyl compounds

The kinetics of the decomposition of the phthalimid-N-oxyl radical (PINO) in acetic acid has been studied. The rate constants of the addition of the radical to T bonds of molecules of vinyl compounds – styrene, methyl methacrylate, acrylonitrile, and methyl acrylate – have been measured. It was shown that electron-donor substituents in the monomer molecule increase, while electron-acceptor substituents decrease the rate of addition. The reactivity of monomers in the elementary step of addition of the PINO radical decreases in the order CH₂=C(CH₃)C₆H₅ > CH₂=CHC₆H₅ > CH₂=C(CH₃)COOCH₃ > CH₂=CHCOOCH₃ > CH₂=CHCN.     

Syntheses of di- and tetrahydropyrroles

The constants and thermodynamic parameters of the ring-chain tautomeric equilibrium of p-substituted (benzene ring) 2,3,3-trimethyl-1-aryl-2-hydroxy-5-pyrrolidones in aqueous pyridine solution were determined by PMR spectroscopy. Conversion of the ring tautomer to the open form is accompanied by an increase in the enthalpy and entropy. The AH value decreases by a factor of 2.8 kcal/mole on passing from electron-donor substituents to electron-acceptor substituants, whereas the AS value remains approximately constant and decreases by 2–4 eu only for strong electron acceptors (COOCH₃, CN, and NO₂). The correlation between the free energies and the a substituent constants in the benzene ring is discussed.See [1] for communication XII.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 634–638, May, 1977.     

Intramolecular charge transfer complexes—25. Copolymers of N-ethyl-3-hydroxymethyl phenothiazinyl acrylate and methacrylate with acryloyl and methacryloyl-β-hydroxyethyl-3,5-dinitrobenzoate

Copolymers with pendant electron-donor and electron-acceptor groups (phenothiazine and dinitrobenzoate type respectively) have been studied. The formation and the participation in the reaction of an intermonomer charge transfer complex was indicated by considering the copolymerization data and by means of electronic absorption and ¹H-NMR spectra. It was concluded from NMR spectra that the acrylate-acrylate copolymers are stronger charge transfer complexes than the methacrylate-methacrylate copolymers.     

Influence of solvation and adsorption on acid-base properties of o-nitrophenol

Transmission spectra were obtained of o-nitrophenol in aqueous solutions at various pH values and in the adsorbed state on the surface of monocation-substituted forms of kaolinite. An interpretation of the electronic spectra of the adsorbed indicator was carried out using quantum-chemical calculations by the CNDO/2 and PPP SCF MO LCAO methods, taking into account the disturbing effect of cations within a point charge model. It was found that the mechanism of the interaction of the dye molecules with active centers on a solid suface differs from its behavior in solution, and this results in changes in the acid-base properties of o-nitrophenol due to changes in the phase composition of the medium. It was concluded that the indicator molecules are adsorbed simultaneously on electron-acceptor and electron-donor centers of the aluminosilicate surface.Translated from Teoreticheskaya i Éksperimental'naya, Khimiya, Vol. 25, No. 2, pp. 226–230, March–April, 1989.     

An energy decomposition scheme applicable to strongly interacting systems

An energy decomposition scheme useful for the analysis of the coupled types of interactions in strongly interacting systems is developed within the Hartree-Fock approximation. A dominant characteristic of the scheme is that it involves the interactions between vacant orbitals of component molecules, as can be justified from the third-order perturbation theory. On the basis ofab initio molecular orbital calculations, the utility of the scheme is illustrated for the BH₃-NH₃ complexation and the S_N2 reaction of CH₄ with H^–. It is found that the charge transfer from electron donor (i.e. NH₃ or H^–) to acceptor (i.e. BH₃ or CH₄) is strongly coupled with the polarization of the acceptor, to contribute appreciably to the stabilization of the entire system. A specific role of this coupling mode in the progress of reactions is discussed.     

Copolymers with Pendant Electron-Donor and Electron-Acceptor Groups

This paper is concerned with charge transfer complex properties of copolymers with pendant electron-donor and electron-acceptor groups obtained by radical copolymerization. The complexing groups were carbazolyl, anthryl, phenothiazinyl, and p-dimethyl-aminobenzyl as electron-donor groups, and picryl, dinitrophenyl, dinitrobenzoyl, and trinitrofluorenyl as electron-acceptor groups. The microstructure of such copolymers, including the tendency to alternating and coisotactic addition, together with the influence of monomer structure and reaction conditions, is discussed. Intramolecular complexation interactions are analyzed. These properties were measured by means of ¹H-NMR and electronic absorption spectra. Finally, some physical properties, e.g., color, solubility, density, and photoconductivity, are presented to illustrate the intramolecular and intermolecular complexation interactions. It is concluded that such copolymers are weak charge transfer complexes of the π-π type. They are of theoretical interest for study of the correlation between synthesis, structure, and properties, and of practical interest due to their optoelectric properties.     

Research on perinone compounds

11-Substituted 14H-benz[4,5]isoquinolino[2,1-a]perimidin-14-ones were synthesized, and their spectra were studied. In contrast to electron-acceptor substituents, electron-donor substituents have little effect on the shift of the absorption maxima. In the reactions of 1,8-naphthalenediamine with various 4-substituted naphthalic anhydrides, electron-donor substituents have little effect on the shift of the absorption maxima. In the reactions of 1,8-naphthalenediamine with various 4-substituted naphthalic anhydrides, electron-donor substituents lead primarily to 10-substituted naphthaloperinones, whereas electron-acceptor substituents lead primarily to 11-substituted naphthaloperinones. An assumption regarding the mechanism of the formation of 10- and 11-substituted naphthaloperinones is expressed.See [1] for communication IV.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1649–1654, December, 1974.     

Stereoelectronic effect in reactions of phosphoester bond rupture

The potential surface profile of the interaction of the anion (CH₃O)₂PO₂ ^– with the nucleophile CH₃O^– in the gas phase and in aqueous solution has been calculated by the AMl method. The energy of the transition state of the reaction in the gas phase is very much dependent on the position of the equatorial methoxy group; the change in the activation barrier amounts to 6 kcal/mole. The stereoelectronic effect is due to electrostatic interaction of the dipole moment of the equatorial substituent with the charge of the attacking or leaving group. An accounting for solvation gives a considerable decrease in the stereoelectronic effect.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2528–2532, November, 1990.     

Modified molecular charge similarity indices for choosing molecular analogues

Toward the goal of defining a molecular charge similarity idex that best quantifies the concept of molecular similarity as it relates to biological activity, we have evaluated a variety of definitions of the molecular charge distribution function, ρ, for use in the charge similarity index formalism. Spatially distributed nuclear charges are incorporated into electron distribution functions to approximately account for the screening of core electronic charge and to model the net effect of the total charge distribution in a manner that better reflects the inherent relation to the molecular electrostatic potential. The resulting charge similarity indices are evaluated based on their sensitivity to relative molecule displacement and their ability to meaningfully group or order a simple set of molecular structures: CH₃CH₂CH₃, CH₃OCH₃, and CH₃SCH₃.     

A theoretical approach to substituent effects. Interactions between directly bonded groups in the neutrals X?NH2, X?OH,and X?F and the anions X?NH− and X?O−

Ab initio molecular orbital calculations have been carried out for the neutrals X? NH₂, X? OH, and X? F and the anions X? NH^? and X? O^? with substituents X = Li, BeH, BH₂, CH₃, NH₂, OH, and F. All structures have been fully optimized with the 4-31G basis set which is found to perform considerably better than the minimal STO-3G basis in predicting the lengths of strongly polar bonds. A quantitative analysis of interactions between the directly bonded groups, utilizing energy changes in hydrogenation reactions, is presented and rationalized with the aid of perturbation molecular orbital theory. Favorable interactions occur when electron-donor groups bond to electron-acceptor groups. This applies to both σ and π interactions, the relative importance of which depends on the particular substituents.