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1.
Summary Several carboxy-substituted ferrocene compounds are prepared and investigated by cyclic voltammetry in acetonitrile solution. The half-wave potentials of most of the acids studied (E 1/2=0.34–0.58 V versus s.c.e.) are more positive than that of ferrocene (0.33 V), reflecting a diminished susceptibility to oxidation of these compounds relative to the parent metallocene. Only -ferrocenylpropionic acid (0.325 V) is effectively identical with the latter in its oxidation behaviour, and -ferrocenylbutyric acid (0.31 V) tends to be more readily oxidized. The results are of interest for subsequent chemical oxidation studies of ferrocenylcarboxylic acids.  相似文献   

2.
Distribution of the unpaired electron in the first free MO, the partial bond orders created by this electron, and the energy level corresponding to it in anion radicals of the nitrofuran series have been examined on the basis of quantum-chemical calculations by the MOH method of the -electron system of 5-nitrofuran and its 2-substituted derivatives. Distribution of the spin density of the electrons in the anion radicals has also been calculated by McLachlan's method. The parameters of the first free MO obtained by calculation agree satisfactorily with the physicochemical characteristics of the corresponding particulars measured experimentally (HFS constants in the EPR spectra and polarographic half-wave potentials).  相似文献   

3.
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.  相似文献   

4.
Zusammenfassung Die polarographischen Halbwellenpotentiale der Perchlorate von Tl(I), Rb(I), K(I), Na(I), Ba(II), Zn(II), Cd(II), Mn(II), Co(II), Ni(II) sowie von Bisbiphenylchrom(I)jodid wurden in Dimethylsulfoxid, Dimethylformamid, Trimethylphosphat und Nitromethan gemessen. Die gemeinsame Diskussion mit den schon bekannten Werten der Halbwellenpotentiale dieser Ionen in Äthylensulfit, 1,2-Propandiolcarbonat, Acetonitril und Wasser führt zum Ergebnis, daß die Lage des Halbwellenpotentials eines Ions, bezogen auf dasjenige von Bisbiphenylchrom(I) mit steigender Donorzahl des Lösungsmittels zu negativeren Werten verschoben wird. Die Kurven imE 1/2 vs. -Diagramm nehmen bei vorwiegend elektrostatischer Solvatation einen anderen Verlauf, als bei stärker kovalentem Bindungscharakter der Solvatbindungen.
Polarographic half-wave potential and solvation of metal ions
The polarographic half-wave potentials are reported for the perchlorates of Tl(I), Rb(I), K(I), Na(I), Ba(II), Zn(II), Cd(II), Mn(II), Co(II), Ni(II) as well as for bisbiphenylchromium(I) iodide in dimethyl sulphoxide, dimethylformamide, trimethyl phosphate and nitrobenzene. For the discussion the half-wave potentials of these ions in ethylene sulphite, 1.2-propanediol carbonate, acetonitrile and water are included. It is shown that the value for the half-wave potential of an ion referred to that of bisbiphenylchromium(I) iodide is shifted to more negative potentials, by increasing donor number of the solvent. The curves in theE 1/2 vs. -diagram are different for ions solvated mainly due to electrostatic ion-solvent interactions from those with more covalent character of the solvate bonds.
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5.
Polyacetylene, (CH)x, has been doped with trimethyloxonium hexachloroantimonate, (CH3)3O+SbCl(1), in dichloromethane and acetonitrile. The maximally doped (CH)x films have moderate conductivities [σRT(CH2Cl2) = 10, σRT(CH3CN) = 0.7 Ω?1 cm?1]. Reactions between 1 and (CH)x CH2Cl2 or CH3CN were followed in situ by 1H nuclear magnetic resonance spectroscopy and x-band electron spin resonance spectroscopy. It was found that the reactions in the two solvents are different. In dichloromethane the dopant is SbCl5, which forms from the decomposition of 1, and doping proceeds by electron removal from (CH)x chains. Based on the ESR signal loss, an estimate can be made of the diffusion rate of SbCl5, into the (CH)x fibrils in CH2Cl2; it is found to be ca. 10?17 cm2/s. In acetonitrile the dopant appears to be either CH3CNCH, H+, CH, or a combination of one or more of these dopants. It is postulated that the CH3CNCH, CH, and/or H+ dopant covalently binds to the (CH)x chain. X-ray photoelectron spectra show that films doped with excess 1 in both solvents have approximately one SbCl per 33 CH units.  相似文献   

6.
The electronic effect of substituents on the acid-base properties of 6- and 7-substituted 2-thionolepidines and 4-thionoquinaldines were investigated. It is shown that the pK a (–H+) values for 6- and 7-substituted 2- and 4-thioquinolones and the pK a (+H+) values for 7-substituted 2-thionolepidines and 6-substituted 4-methylmercaptoquinaldines correlate with the M substituent constants of Jaffe and Taft. The effect of a substituent is transmitted primarily via an inductive mechanism, regardless of its position.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 399–402, March, 1974.  相似文献   

7.
Hydrogenation of 6- or 8-R-substituted quinaldines [R=H, CH3, CH(CH3)2, C(CH3)3, or CF3] over platinum in trifluoroacetic acid gave higher yields (90%) of 5,6,7,8-tetrahydroderivatives than hydrogenation of the corresponding quinolines. ThepKa-values of 20 quinolines and quinaldines were determined by measuring the half-neutralization potentials in acetic anhydride. More basic quinolines gave higher yields of 5,6,7,8-tetrahydroproduct; exceptions are 6- and 8-methylquinoline and 8-tert. butylquinoline. Explanations for these observations are suggested.Dedicated to Prof. Dr.K. Schlögl on the occasion of his 60th birthday.  相似文献   

8.
The natural abundance 13C n.m.r. spectra of a series of para-substituted ethylbenzenes, 4-substituted-1-ethylnaphthalenes and a limited series of 6-substituted-2-ethylnaphthalenes have been examined at low dilution in deuterochloroform solvent. The ethyl carbons and Cipso in the phenyl series (i.e. have been assigned, and substituent chemical shifts for these carbons calculated and analysed by the Dual Substituent Parameter treatment. (Chemical shifts of all ring carbons have been obtained, but not assigned). Generally speaking, electron-withdrawing substituents lead to positive (i.e. downfield) substituent chemical shifts for CH 2 and negative substituent chemical shifts for C H3, i.e. ‘normal’ and ‘inverse’ behaviour respectively. Cipso in the phenyl series exhibits a ‘normal’ dependence. The dependences of the various substituent chemical shifts on inductive and resonance parameters are discussed, and compared with the behaviour of side chain carbons in other substituted benzene systems.  相似文献   

9.
Radical polymerization of 4-pentamethyldisilylstyrene ( 1 ) and 4-pentamethyldisilyl-α-methylstyrene ( 2 ) have been conducted. Monomer reactivity ratious (r1 and r2) of 1 and 2 with styrene (M1) were measured with Fineman-Ross plots. The resonance factor (Q) and polar factor (e) of a Q–e scheme for 1 were conculated with the r1 and r2 values. The inductive effect (σI) resonance effect (σ) of the pentamethyldisily group were monitored with the 1H- and 13C-NMR spectra of 1 . The magnitudes of σI and σ were found to be analogous to those of the trimethylsilyl group, indicating that the disilyl group shows a net electron-withdrawal effect  相似文献   

10.
The solvolysis rates and products of 4- and 5-exo-substituted 2-exo- and 2-endo-norbornyl tosylates 9 and 10 , respectively, are reported. The logarithms of the rate constants (log k) correlate linearly with the inductive constants σ for the substituents. A comparison of the reaction constants p1 for the 4-, 5-, 6-, and 7-substituted 2-exo- and 2-endo-tosylates 9 , 10 , 1 , and 2 respectively, indicates that inductivity is higher for 2-exo-ionization than for 2-endo-ionization in all series. This observation is attributed to the more favorable alignment of neighbouring C-atoms for dorsal participation in exo-ionization, especially, in the case of C(6).  相似文献   

11.
Kinetics of oxidation of twenty six S-arylmercaptoacetic acids (SAMA) (I) by sodium perborate (PB) have been studied in acid medium. The product of oxidation is the corresponding thiophenol. The rate data of meta-and para-substituted acids have been correlated with DSP equations. While the para-compounds correlate well with σI and σR° values, the meta-compounds correlate well with σI and σ values. The reaction constants are negative and of smaller magnitudes. Further, the ortho-substituted acids show a good correlation with a triparametric equation involving Taft's σI and R° and Charton's steric parameter ν. There is a considerable steric contribution to the total ortho-substituent effect. Based on these observations, mechanism involving the formation of protonated arylsulfinylacetic acid intermediate, followed by an intramolecular rearrangement leading to the product thiophenol has been proposed. © 1995 John Wiley & Sons, Inc.  相似文献   

12.
The mass spectra of a series of thirteen m- and p-substituted benzils have been determined at several ionising voltages below 20 eV and at 70 eV. At ionising voltages up to 5 eV above the ionisation potentials the benzil molecular ions decompose entirely by two pathways to give substituted and unsubstituted benzoyl ions. Fractional intensities of the molecular ion (FM), substituted (FX) and unsubstituted (FH) benzoyl ions were obtained for each benzil as a function of energy from measured ionisation efficiency curves, and ionisation and appearance potentials for all major ions determined from the ionisation efficiency curves by a semilogarithmic method. Various correlations of ion intensity and energy parameters with δ+ and δ constants are examined; these are generally poor. Fair correlations are obtained between log (FX/FH) or (AP – AP) and δ or δ+, and these are interpreted in terms of the expected effect of substituents on the stabilities of the product ions in the decompositions. A good correlation is observed between log (FX/FH) and AP · AP; this suggests that substituents affect FX/FH mainly by changing the activation energies for the competing decompositions of the molecular ions. The competitive shift has a marked effect on these appearance potentials so that in this system AP – IP is not a good measure of the activation energy for the primary decompositions.  相似文献   

13.
《Thermochimica Acta》1987,119(2):273-283
The electron transfer processes in the oxidation reactions of a series of N,N-dimethyl-4-substituted anilines in liquid and gaseous phases were studied. By means of a linear regression analysis, half-wave oxidation potentials in acetonitrile. ionization potentials in the gaseous phase, substituent constants and ionization constants of conjugated acids in water or water-alcohol mixtures are related. A thermodynamic cycle allows the calculation of the solvation energies of both radical cations and parent free bases.  相似文献   

14.
Peaks of molecular ions that generally have the maximum intensity are observed in the mass spectra of most of the investigated 5- and 6-substituted uracils and 5-substituted orotic acids and their deutero analogs and methylated derivatives. The principal pathway of the fragmentation of the molecular ions is retrodiene fragmentation with the formation of [O=C(4)C(5)R5C(6)R(6)N(1)R1]+ (F1) ions. The stabilities of the latter depend on the nature and position of the substituents attached to the C(5) and C(6) atoms. The fragmentation of the F1 ions can be realized via four principal pathways (B-E) with the detachment of N-CR6 (B), O=C=CR5 (C), CO (D), and R6 (E) fragments. The most general pathway for the fragmentation of 5-substituted uracils is pathway C, whereas the most general pathway for 6-substituted uracils is pathway E. In the spectra of 5-substituted orotic acids the intensities of the molecular-ion peaks are high (100%) only in the case of electron-donor R5 and decrease sharply with an increase in the electron-acceptor strength of the substituent. The principal pathways of fragmentation of the molecular ions are decarboxylation (F) and retrodiene fragmentation (A), the contribution of which is appreciably smaller. The M-CO2 ions formed after decarboxylation undergo fragmentation via a scheme similar to that observed for 5-substituted uracils.See [1] for Communication 75.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 520–531, April, 1990.  相似文献   

15.
Ultraviolet irradiation of the aldehydes 6 – 11 in degassed solutions results exclusively in decarbonylation to the major products 34, 35 and 37 – 40 , and to small amounts of 2, 3-diphenyl-2, 3-dimethyl-butanes 36 from the phenyl aldehydes 6 and 7 . In the presence of tri-n-butylstannane, incorporation of stannane hydrogen competes, to substrate-specific limits, with the intramolecular deuterium transfer in 7 → 35 and 11 → 40 . The quantum yields for decarbonylation are Φ ~ 0.4–1.0 for the phenyl aldehydes 6 and 9 , and 0.02 for 8. Hammett correlations of Φ with resonance constants ( R ) for 6 (X = H, p-CH3, ? OCH3) and (? CF3) and with ωm+ values for the meta-substituted isomers are in agreement with the proposed α-cleavage to an associated radical pair with only moderate free radical character as the primary photochemical step. Φ for 10 (X = H) is 0.11, and for 10 (X = OCH3) 0.065. It is noteworthy that decarbonylation of 10 (X = OCH3) occurs also at 3340 Å (Φ? CO = 0.11) i.e., upon excitation in an absorption band which is presumably lower in energy than the n → π* transition and corresponds to the aromatic Lb transition of 2-methoxynaphthalene. Singlet multiplicity of the reactive excited states is probable on the basis of the fact that the decarbonylation of 6 (X = H) and 10 (X = H and OCH3) could be sensitised neither by acetone nor acetophenone, and could be quenched neither by naphthalene nor by cis-1, 3-pentadiene and nor by 1, 3-cyclohexadiene.  相似文献   

16.
17.
The influence of substituents on the 13C NMR chemical shifts of 2-substituted 1-methylbenzimidazoles has been investigated. The electronic effects of the substituents are transmitted to C-4 and C-7 mainly by the resonance mechanism, and to C-5, C-6 and N-CH3, by approximately equal contributions of the resonance and inductive components. A critical analysis of the share in the transmission of substituent effects through the ‘pyridine-type’ and ‘pyrrole-type’ nitrogen atoms is given.  相似文献   

18.
The barrier to internal rotation around the phenyl–carbonyl bond in a series of stable protonated p-substituted acetophenones has been determined by means of low temperature 13C NMR and total bandshape analysis resulting in a value of ΔG = 48.1 kJ mol?1 for the unsubstituted protonated compound. The energy results and the 13C chemical shifts are in good agreement with the quasi-planarity of the ground state in p-substituted protonated acetophenones. The barrier heights are discussed in terms of contributions from steric and resonance effects.  相似文献   

19.
The magnesium bromide-diethyl etherate-catalyzed ring-opening of (3-(naphthalen-2-yl)-2,2-bis(trimethylsilyl)oxiran 2 with thiophenols affords (1-trimethylsilylvinyl)sulfides 3 and the (1-bromovinyl)silane 4. Nucleophilic attack occurs regioselectively at the position α- to silicon. The compound 2 has been converted into the (1-trimethylsilylvinyl)amide 5 with an excess of acetonitrile and into the (1-trimethylsilylvinyl)acetate 6 with acetic acid/acetic anhydride. These reactions proceed with catalytic amounts of boron trifluoride-diethylether. Treatment of 2 with acetic acid alone gives naphthaldehyde. The epoxide 2 reacts also with MgBr2·OEt2, MeLi/CuI, HX (XBr or Cl) and LiAlH4 with nucleophilic attack at the bis(trimethylsilyl)-substituted carbon.  相似文献   

20.
Summary Half-wave potentials for a one-electron reduction of copper(II) complexes containing polydentate ligands can be calculated using the equationE 1/2=E 0(Cu2+/+)+ i j E i where E i are contributions related to the electronic and steric properties of the ligands. The values of 18 E i contributions are presented and explained, and the effect of the solvents on the half-wave potentials is exemplified.Dedicated to Prof. Dr. Viktor Gutmann to his 70th birthday  相似文献   

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