A quantum-mechanical study of the inductive and steric effects for the example of <Emphasis Type="Italic">tert</Emphasis>-butylalkanes

A relation between the inductive and steric effects (concepts of the classical theory of molecular structure) and electron density distribution parameters was revealed by quantum chemistry methods. The propagation of the inductive and steric influence of the (CH₃)₃C and CH₃ groups along carbon chains in tert-butylalkanes was analyzed. The steric effect of the (CH₃)₃C group was shown to extend to two CH₂ groups, and the inductive effect, to one CH₂ group. Definitions of the standard (CH₃)₃CCH₂ and (CH₃)₃C(CH₂)₂ groups were given. Configurations of transferable groups decreasing additive approach errors were suggested. Additive procedures for calculating the properties of molecules containing (CH₃)₃C were refined.     

Inductive effects on molecular ionization potentials—X: Alkyl and hydrogen halides

The ionization potentials of alkyl and hydrogen halides are found to be excellent linear fractions of the polar and inductive substituent constants, indicating that the effect of alkyl substituents on the electron density of the halogen atoms is inductive. The slopes of the four regression lines vary widely in the order RF ? RCl > RBr > RI, which shows that the susceptibility of the halogen atoms to inductive effects varies in the same order. Values of σ_I and σ^* for alkyl groups not previously available are estimated.     

Acidities of 1-indolylacetic and carbazolylacetic acids. Inductive constants of indolyl and carbazolyl groups

The pK_a values of 1-indolylacetic, 3-(9-ethyl)carbazolylacetic, and a number of 3,6-disubstituted 9-carbazolylacetic acids in aqueous ethanol solutions were determined by potentiometry.The inductive constants of the corresponding heterocyclic fragments were calculated from the values obtained. It is shown that annelation of the benzene ring with the pyrrole ring of indole gives rise to a decrease in the negative inductive effect of the heteroring. A linear relationship between the acidic properties of carbazoles and the corresponding 9-carbazolylacetic acids was established.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1654–1657, December, 1981.     

Polar Effects in the Solvolysis of 4-Substituted Bicyclo [2.2.2]octyl p-Nitrobenzenesulfonates. Polar effects. VII

Hydrolysis of bicyclo[2.2.2]octylp-nitrobenzenesulfonate ( 14a , X = p-NO₂C₆H₄SO₃), and nineteen 4-R-substituted derivatives 14b–14t in 70% aqueous dioxane yield the corresponding bicyclo[2.2.2]octanols 14 (X = OH), exclusively. The 7-center fragmentation to 1,4-dimethylidene-cyclohexane ( 15 ) is not observed. The logarithms of most of the rate constants, measured in 80% ethanol, correlate well with the corresponding inductive substituent constants σ of R. Hence, in these cases ionization rate is controlled by the inductive effect of R only. Poor correlations result when the substituents are potentially electrofugal groups, such as COO^?, CH₂OH, CH₂NH₂, CONH₂ and H, the deviations from the inductive regression line corresponding to rate enhancements of 1.6 to 8. These exalted substituent effects are tentatively ascribed to extended hyperconjugation involving two σ-bonds. This study corroborates previous evidence that the inductive effect alone does not fully account for the polar effect of some substituents in reactions involving carbocations.     

石墨烯/尖晶石LiMn2O4纳米复合材料制备及电化学性能

采用溶胶凝胶法和还原氧化石墨法制备尖晶石LiMn2O4纳米晶和石墨烯纳米片,并采用冷冻干燥法制备了石墨烯/尖晶石LiMn2O4纳米复合材料,利用XRD、SEM、AFM等对其结构及表面形貌进行表征;利用CV、充放电、EIS研究纳米复合材料的电化学性能和电极过程动力学特征。结果表明:纳米LiMn2O4电极材料及其石墨烯掺杂纳米复合材料的放电比容量分别为107.16 mAh.g-1,124.30 mAh.g-1,循环100周后,对应容量保持率为74.31%和96.66%,石墨烯可显著改善尖晶石LiMn2O4电极材料的电化学性能,归结于其良好的导电性。纳米复合材料EIS上感抗的产生与半导体尖晶石LiMn2O4不均匀地分布在石墨烯膜表面所造成局域浓差有关,并提出了感抗产生的模型。     

Influence of the polarization effect on the donor properties of 1-phenylsilatrane

A new mechanism of the dipole—induced dipole polarization interaction was considered to explain an anomalous increase in the +I effect in a 1-phenylsilatrane molecule with the pentacoordinated Si atom. The interaction through the space between the silatrane cage having a high dipole moment and easily polarizable aromatic phenyl substituent induces dipole that adds the influence of the inductive effect along the bonds, which is characteristic of usual silatranes. The high inductive constant σ_I calculated for 1-phenylsilatrane on the basis of chemical shifts δ_C of aromatic carbon atoms was interpreted as a superelectronodonor effect in silatranes. However, the polarization effect through the space leads to a substantial change in the chemical shifts δ_C for the phenyl group in the direction that formally corresponds to the enhancement of the +I effect transmitted via the bonds. It is shown for the first time that the inductive effect in silatranes is not constant and varies according to the polarizability of the substituent at the Si atom.     

Correlations of substituent parameters with the carbonyl stretching force constant in arenetricarbonylchromium complexes

Correlations are established between selected substituent parameters (σ_I,σ_P, σ_R^P,σ_P^O,σ_R^O) and the carbonyl stretching force constant, k(CO), for 28 mono and poly-substituted tricarbonylchromium-complexed arene compounds. On the basis of the statistical results it is concluded that the overall electronic substituent effect transmitted to the carbonyl groups involves both mesomeric and inductive mechanisms. Within the restricted domain, including substituent group and benzene ring, transmission proceeds largely by resonance, with a minor inductive (through-bond and field) effect operative in the same domain. Further transmission from the substituted arene ring to the chromium atom predominantly involves an inductive mechanism. This result, in support of existing literature data, suggests appreciable participation of the ring carbon σ framework in the metal—ring bond formation.     

Inductive substituent constants σji from olefinic geminal 1h, 1h nmr coupling constants

Theoretical and experimental arguments are presented supporting the postulate that olefinic NMR coupling constants ²J_HH are insensitive to β-substituent influences on the olefinic π orbital. A new set of substituent constants, σ^J_I, is proposed to measure directly the inductive substituent effect transmitted by σ-bonds. The previously available range of inductive substituent constants can be appreciably extended in this way. Comparisons of σ^J_I with other observables and parameters for selected substituents are made as a test of consistency.     

Substituent effect on the formation of organically-modified silicate-phosphate alternating copolymer through nonaqueous acid–base reaction

Organically-modified silicate-phosphate and silicate-phosphite copolymers were prepared through nonaqueous acid–base reaction. The inductive effect of the organic substituent of the starting materials such as organically-modified chlorosilane and phosphorous acid on the acid–base reaction was investigated by ³¹P NMR measurement and ab initio molecular orbital calculation. The condensation reaction takes place by nucleophilic addition of phosphate ion (or phosphite ion) to chlorosilane through S_N2 mechanism to form silicate-phosphate (or phosphite) network. The reactivity of the acid–base pair can be controlled by changing the inductive effect of the organic substituents on the starting materials.     

关于在钾与负氢混合物中钾钙嬗变的检测

报道了在室温下钾与负氢混合物中钾钙发生嬗变的现象，负氢是由NaBH₄、LiBH₄和NH₃BH₃提供的.实验中的钾和钙的浓度分别用诱导耦合等离子发射光谱法（ICP-OES）和诱导耦合等离子质谱法（ICP-MS）进行检测.ICP-OES结果表明随着混合物中钾浓度的降低伴随着钙的浓度增加.此外ICP-MS结果还表明⁴⁰Ca浓度的增加伴随着⁴¹K浓度的增加，可能表明在负氢存在的条件下混合物中⁴⁰Ca的生成与⁴¹K物种有关.     

A 19F NMR study of the transmission of electronic effects in triarylantimony and triarylbismuth compounds. A comparison with the nitrogen- and carbon-containing analogues

A ¹⁹F NMR study of the transmission of electronic effects has been made for the systems Ar₂EC₆H₄F-4 (E = Sb, Bi, CH, N). The fluorine chemical shifts obtained are correlated with the polar constants (Σσ^o and Σσ) of the substituents, suggesting that electronic effects are transmitted through the SbC_ar, BiC_ar and CC_ar bonds predominantly by an inductive mechanism, whereas the transmission through the NC_ar bonds is contributed to significantly by classical resonance effects due to competitive conjugation of the lone pair with the aromatic rings, and the substituents therein. A dual parameter correlation of the fluorine chemical shifts with the inductive (σ_I) and resonance (σ^o_R and σ_R) parameters of the substituents in the aromatic rings has led to similar conclusions. The inductive transmission through the bridging Sb and Bi atoms has been assigned to the absence of conjugation of lone pair and vacant d-orbitals of the metals with π-electron systems of the aromatic rings. On the basis of the values of the ? coefficients for the correlation equations obtained it has been established that the transmitting ability of the BiC_ar bonds is close to that of the C_alC_ar bonds and considerably lower than the transmitting ability of the NC_ar bonds.     

Silane. XII. Alkalische Solvolyse von substituierten Benzylsilanen

Alcaline solvolysis of substituted phenyl and benzyl silanes listed in “Inhaltsübersicht” is compared. The inductive transfer coefficient of the CH₂ group is fixed.     

Interactions of different heterocyclic compounds with monoionic forms of montmorillonite

Interactions of 3-R-and 2-R pyridine (R=CH₃, Cl, NH₂) with Ni(II)-exchanged montmorillonite have been studied. Thermal and X-ray analyses indicate that pyridine derivatives are intercalated into the interlayer spaces of montmorillonite. Infrared spectral data shown that the Lewis and/or Brönsted type of interactions of pyridine derivatives is connected with different steric and inductive effects of the substituents (R) on the pyridine ring. The alkylpyridines increase the electron density on the donor nitrogen atom and support the coordination to the central atom. The halogen substituents have a negative inductive effect (–I), so that those ligands show a lower basicity and weaker σ-bonding properties than pyridine and also the lower possibility of the coordination.     

n-π Interactions in homoallylic methyl ethers a photoelectron spectroscopic study

The He I photoelectron spectra of several monocyclic and bicyclic methoxy compounds have been interpreted in terms of inductive effects and n-π interactions between the π_cc molecular orbital and the oxygen lone pair orbital n_o. The n-π interactions appear to be small, and are mainly through bond.     

On the stabilization of carbanions by adjacent phenyl,cyano, methoxy-carbonyl,and nitro groups in the gas phase

Institute of Mass Spectrometry, University of Amsterdam, Amsterdam, The Netherlands By using the method of Fourier transform ion cyclotron resonance mass spectrometry, substituent stabilization energies of homologous series of cycloalkyl carbanions, Ξ-c-C_nH_2n?2 (n = 3, 4, 5, 6, 7) with π-accepting substituents (Ξ = Ph, CN, COOMe, NO₂) have been determined experimentally in the gas phase as the difference between the proton affinity of the substituted and corresponding unsubstituted (Ξ = H) cycloalkyl carbanions. The stabilization energy data have been analyzed in terms of Taft’s parametrization of polarizability, field/inductive, and resonance effects. The linear regression analyses show excellent correlations within the ΞCH₂ ^? Ξ-c-C_nH_2n?2 ^? (n = 4, 5, 6, 7), and Ξ-c-C₃H₄ ^? carbanion series, from which it appears that the contributions of polarizability effects are independent of the above type of carbanions and only depend on the nature of the substituent. Further, it follows that inductive stabilization is more effective in the substituted methyl, ΞCH₂ ^?, than in the substituted cycloalkyl, Ξ-c-C_nH_2n?2 ^? (n = 4, 5, 6, 7) carbanions. This result suggests that inductive stabilization is counteracted by the electron releasing effect of alkyl groups. Resonance stabilization is significantly more effective in the substituted cycloalkyl, Ξ-c-C_nH_2n?2 ^? (n = 4, 5, 6, 7), than in the substituted methyl, ΞCH₂ ^?, carbanions, which suggests that m contrast to inductive stabilization, resonance stabilization is assisted by the electron releasing effect of alkyl groups. Finally, it appears that substitutent stabilization in the geometrically restricted substituted cyclopropyl carbanions, Ξ-c-C₃H₄ ^?, is dramatically less effective than in the corresponding geometrically unrestricted larger substituted cycloalkyl carbanions, Ξ-c-C_nH_2n?2 ^? (n = 4, 5, 6, 7). The linear regression analyses of the substituted cycloalkyl carbanions indicate that reduction of the stabilization energy is caused not exclusively by a geometrically hindered resonance stabilization, but also to a smaller extent by a less efficient inductive stabilization in the substituted cyclopropyl carbanions.     

Acetolyses of π-irontricarbonyl complexes of 2,3-dimethylidene-7anti-norbornyl and 5,6-dihethylidene-2exo-morbornyl esters.

Homodonjugative stabilization of a carboction by the exocyclic diene-Fe(CO)₃ group can compete with its destabilizing inductive effect.     

A HeI photoelectron spectroscopy and theoretical study of 2,6-dichloropyrazine, 2,3-dichloropyrazine, 4,6-dichloropyrimidine and 3,6-dichloropyridazine

The electronic structures of C₄H₂Cl₂N₂ isomers have been studied by HeI photoelectron spectroscopy (PES) combined with the outer valence Green’s function (OVGF) calculations at 6-311++G(d,p) basis sets. The vertical first ionization potentials for 2,6-dichloropyrazine, 2,3-dichloropyrazine, 4,6-dichloropyrimidine and 3,6-dichloropyridazine are determined to be 9.93, 9.89, 10.45 and 10.07 eV, respectively, and the PE spectra were assigned based on molecular orbital analysis and by comparison with related compounds. The effects of chlorine substituent and different positions of nitrogen atoms in these C₄H₂Cl₂N₂ isomers have been carefully analyzed by comparing the C₄H₂Cl₂N₂ isomers with their matrixes (pyrazine, pyridazine, pyrimidine). The inductive effect of chlorine substituent leads to the stabilization of the nitrogen lone pair orbitals. The resonance effect predominates over the inductive effect, and the consequence is the destabilization of the π orbitals. Owing to the different positions, the effects of nitrogen atoms are different and lead to the different sequence of π orbitals.     

A successful separation of position-dependent inductive effects for the basicities of quinolines

The substituent effects on the basicities of 3-, 4-, 5-, 6-, and 7-substituted quinolines were separated into inductive(ρ_iσ_i) and pi-electronic(ρ_πσ_π) components for each position by means of the LSFE equation, whose C_ij (=ρ_i/ρ_i,4α) set derived was essentially equal to that for the solvolysis of 1-(1-naphthyl)ethyl chlorides.