薄层光谱电化学法测定辅酶B12模型化合物的生成速率常数

用薄层光谱电化学方法和单电位-计时吸收光谱法(SPS-CA),测得钴四苯基卟啉(CoTPP)分别与碘甲烷、苄基氯和氯丁烷形成含σ钴-碳键辅酶B₁₂模型化合物的速率常数为11.09、1.62×10²和6.93×10^-2mol^-1·L·s^-1。钴卟啉与这3种卤代烷的反应是二级反应,对各自的反应物Co(Ⅰ)TPP和卤代烷都是一级反应。     

The ν(OH/OD) band shape of strong hydrogen bonded dimers of phosphinic acids. Phenomenology and formation models

The infrared spectra of phosphinic acid R₂POOH dimers (R=CH₃, CH₂Cl, C₆H₅) have been studied in CCl₄ and CH₂Cl₂ solutions (T=300 K). The infrared spectra of deuterated R₂POOD dimers (R=CH₃, CH₂Cl) were also studied in the gas phase (T=400–550 K) and solid state (T=100–300 K). They are compared with previously studied spectra of the light (non-deuterated) dimers in the gas phase, in the solid state and in low-temperature argon matrices (T=12–30 K) in the 4000–400 cm⁻¹ spectral region. It is found that the strong and broad ν(OH) dimer bands have similar shapes, nearly equal values of bandwidth and low-frequency shift, and possess the Hadzi ABC structure irrespective of the type of acid, significant differences of dimerization enthalpies, influence of solvent, the type of H-bonded complexes (cyclic dimers in the gas phase, in solutions, and in inert matrices, and infinite chains in the solid state), and temperature in the range 12–600 K. Isotopic ratio of the first moments of light and deuterated acid bands has been measured. Analysis of the ν(OH/OD) band of hydrogen bonded dimers of phosphinic acids shows that the interaction between the two intermolecular bonds O–HOP in a cyclic complex plays virtually no role in the mechanism of the ν(OH/OD) band formation; the shape of ν(OH/OD) band is controlled mainly by the POOH(D)O fragment; and the band shape of strong hydrogen bonded complexes is formed by a number of vibrational transitions from the ground state to different combination levels in the region 3500–1500 cm⁻¹.     

Chemie polyfunktioneller moleküle : LXXXVII. Synthese und reaktionsverhalten von 4-methyl-1,2,6-tristiba-tricyclo[2.2.1.0]heptan (Sb3-nortricyclan) gegenüber chrom-, molybdän- und wolframhexacarbonyl

The reaction of CH₃C(CH₂Cl)₃ and NaSb(C₆H₅)₂ in liquid ammonia leads to Sb₂(C₆H₅)₄ (I). Using CH₃C(CH₂Br)₃ instead of CH₃C(CH₂Cl)₃ results in the formation of I and CH₃C[CH₂Sb(C₆H₅)₂]₃ (II). Treatment of II with gaseous HCl in dry CH₂Cl₂ yields CH₃C(CH₂SbCl₂)₃ (III) under elimination of benzene. The reduction of III with Na in THF gives the first all-cis-organocyclotristibane (Sb₃-nortricyclane) CH₃C(CH₂Sb)₃ (IV) which forms the new CH₃C(CH₂Sb)₃M(CO)₅ complexes (Va---Vc) with M(CO)₅THF (M = Cr, Mo, W).     

脂族酰基过氧化物分解动力学的研究(Ⅷ)——过氧化辛酰、过氧化己酰热分解产物的CIDNP效应

测定了过氧化辛酰(1)和过氧化己酰(2)在邻二氯苯中,分别在碘、碘乙烷、2-碘丙烷和3-溴丙烯存在下,90℃时热分解产物的¹HNMR谱,观察到自由基捕获产物(RX,R=n-C₇H₁₅、n-C₅H₁₁;X=I,Br)和歧化产物(R_-H)的CIDNP多重效应。讨论了过氧化酰热分解生成自由基对及相互作用的机理。     

Organopolysilane oligomers bearing transition-metal moieties: Synthesis, reactivities and molecular structure of [η-Me3SiMe2SiC5H4(CO)Fe(CO)2Fe(CO)-η-C5H4SiMe2SiME3]

Reaction of Me₃SiMe₂SiC₅H₅ (4), prepared from Me₃SiMe₂SiCl and C₅H₅Na, with Fe(CO)₅ in refluxing xylene afforded the title compound (3). The silicon-silicon bond in 3 is exceptionally stable in refluxing xylene and also in succeeding reactions to prepare a series of its derivatives. Thus, 3 reacted with I₂ in either chloroform or benzene, giving [η⁵-Me₃SiMe₂SiC₅H₄Fe(CO)₂I] (6). Compound 3 was reduced by sodium amalgam and reacted subsequently with CH₃I, PhCH₂Cl, CH₃COCl, PhCOCl, Cy₃SnCl (Cy = cyclohexyl) and Ph₃SnCl, producing [η⁵-Me₃SiMe₂SiC₅H₄Fe(CO)₂R][7 : R = CH₃ (a), PhCH₂ (b), CH₃CO (c), PhCO (d), Cy₃Sn (e) and Ph₃Sn (f), respectively]. The molecular structure of 3 has been determined by X-ray diffraction crystallography. It was found that 3 has a trans-configuration with a symmetrical centre located at the middle of the Fe---Fe bond. It is abnormal that the conformation of the disilane part around the Si---Si bond is almost eclipsed rather than staggered.     

IR, Raman and theoretical ab initio RHF study of aminoglutethimide — an anticancer drug

A comparative analysis of the IR and Raman spectra of aminoglutethimide (AG) dissolved in CCl₄, CHCl₃ and CH₃CN was performed. Most of the absorption bands were assigned to characteristic group vibrations with the use of the IR and Raman spectra of deuterated AG, glutethimide, N-methyl glutethimide and glutarimide. The AG samples very weakly interacting with the environment were studied with the use of the Ar matrix isolation IR spectra. For comparison, the IR and Raman spectra of the crystalline samples formed by hydrogen-bonded AG molecules were recorded. The spectra were analyzed also in terms of normal modes and the harmonic approximation with the use of the ab initio restricted Hartree-Fock theory. It was found that increasing the solute concentration in CCl₄ and CHCl₃ leads to formation of the autoassociates. In CH₃CN the solute–solvent AG–CH₃CN dimers occur. Possible structures of the associates were theoretically studied on the model systems: the centrosymmetric glutarimide dimer and the linear AG–CH₃CN dimer. By a comparison of the theoretical and experimental spectra we were able to identify several peaks originating from the solute–solvent interactions.     

A flow tube study of methyl iodine uptake on soot surface

The black carbon aerosols are now recognized for their potential impact on climate and the halogenated compounds are thought to be very important in atmospheric chemistry. However, there are very few studies on the interactions between soot aerosols and halogenated compounds. We report the measurement of the uptake of CH₃I on soot. The measured uptake coefficient is 0.0103 ± 0.0015 at a total pressure of 2–4 Torr and 298 K. The results suggest that the uptake of CH₃I occurs efficiently on soot particles. The present work suggests that heterogeneous loss of CH₃I on soot may influence the concentration of CH₃I throughout the atmosphere.     

Anchimeric assistance by γ-substituents Z, Z=MeO, PhO, MeS or PhS, in reactions of the bromides (Me3Si)2(ZMe2Si)CSiMe2Br with AgBF4

The new organosilicon bromides (Me₃Si)₂(ZMe₂Si)CSiMe₂Br with Z=PhO or MeS have been prepared and new spectroscopic data obtained for the previously reported compounds with Z=H, F, Br, Me, Ph, MeO or PhS. Competitions between pairs of bromides for a deficiency of AgBF₄ in Et₂O, with the determination of the ratio of the fluoride products by ¹⁹F-NMR spectroscopy, have led to the following approximate relative reactivities of the bromides and so to the relative abilities of the γ-Z groups to provide anchimeric assistance to the leaving of Br⁻ in this reaction: Me, 1; Ph, 40; PhO, 3400; PhS, 5000; MeS, 7000; MeO, 54 000. In methanolysis in CH₂Cl₂, (Me₃Si)₂(MeOMe₂Si)CSiMe₂Cl has been found to be roughly 120 times as reactive as (Me₃Si)₂(PhOMe₂Si)CSiMe₂Cl. Combination of the results with previously available information suggests the following approximate order of ability of γ-groups Z to provide anchimeric assistance in reactions at the Si---X bonds in compounds (Me₃Si)₂(ZMe₂Si)CSiMe₂X: OCOMe>OMe>OCOCF₃>MeS>PhS, PhO>N₃, Cl>NCS>Ph>CH=CH₂>Me.     

Intermolecular potentials obtained from high-energy alkali scattering

Intermolecular potentials have been obtained from high-energy total cross sections for several alkali metal systems: CS + He, Ne, Ar, CH₃NO₂; K + CH₄, C(CH₃)₄, C₆H₆, c-C₆H₁₂, CH₃I, CCl₄, SF₆, N₂. For the CS-rare gas cases and K + N₂ only the repulsive part was determined. For the rest both attractive and repulsive parts were seen.     

The rearrangement of polyhaloalkyl radicals in solution with 1,2-chlorine atom migration

Radicals XCCl₂CYCH₂Z (l; X=Cl,H,F,CH₃; Y=H,CH₃,Cl,Br; Z=Br,Cl,CCl₃,SR) were generated by homolytic addition of addition of various addenda to unsaturated compounds XCCl₂CY=CH₂. Radicals (I) were shown to rearrange in solution into radicals XCCl---CYCl---CH₂Z (II), the latter being more stable than the former. It was found that compounds XCCl₂CBr=CH₂ with X=Cl,CH₃,F could isomerize under the action of initiators of radical processes to compounds XCCl=CClCH₂Br. This isomerization was proved to be of a radical chain character and involves the 1,2-chlorine migration in the intermediate radical XCCl₂CBrCH₂Br (III). The dependence between the structure of starting radicals and their ability to undergo rearrangement in solution has been established and the effect of the nature of addendum on the reaction course investigated. The polyhaloalkyl radicals were arranged in a sequence according to their relative stability.     

光引发阳离子聚合反应的研究——Ⅱ.硫鎓盐DPTS引发乙烯基正丁醚光聚合动力学

以二苯基-4-苯硫基代苯基硫鎓盐(DPTS)为光引发剂,研究了乙烯基正丁醚的本体和溶液光聚合。在本体聚合中,聚合速率(R_p)与引发剂浓度成正比;在15～35℃范围内,聚合活化能几乎为零。分别以CHCl₃(CH₂Cl)₂和C₆H₅Cl作溶剂的溶液聚合,其R_p均比本体聚合者大,同时单体浓度对R_p的影响则表现出复杂的关系。根据普遍接受的硫鎓盐光解机理并假设溶剂和单体均可不同程度地参与引发反应,解释了溶液聚合中单体影响的动力学规律。     

The performance of B3-LYP density functional theory in describing SN2 reactions at saturated carbon

The performance of the B3-LYP variant of density functional theory when used in conjunction with the 6-31G(d) and 6-311 + G(3df, 2p) basis sets in describing the prototypical gas-phase S_N2 reactions of Cl⁻ + CH₃Cl and CH₃Br has been examined in detail. Reasonable values of the complexation energies (ΔH_comp) for the ion-molecule complexes formed in these reactions are obtained. However, the overall (ΔH_ovr^#) and central (ΔH_cent^#) barriers for these reactions calculated using the B3-LYP functional are significantly underestimated when compared with G2(+) or experimental results. This implies that the B3-LYP energies for the Cl(H₃C)Cl⁻ (D_3h) and Cl(H₃C)Br⁻ (C_3v) transition structures are relatively too low. The B3-LYP errors appear to be systematic, with similar errors being found for corresponding quantities for the two reactions examined.     

Free Rotor Model or Rigid Rotor Model for CH3F-Ne Complex and Comparison with Other CH3F-Rare Gas Systems

The assignment of the rovibrational spectra of molecule-Ne complexes is always a challenge to study van der Waals systems, since they usually exhibit behavior intermediate between free rotor and rigid rotor. In this paper, the microwave and infrared spectra of CH₃F-Ne, a model system for symmetric-top-atom dimer, were firstly predicted and analyzed based on the four-dimensional ab initio intermolecular potential energy surfaces(PESs), which explicitly incorporate the v₃(C-F) stretch normal model coordinate of the CH₃F monomer. Analytic three-dimensional PESs were obtained by least-squares fitting vibrationally averaged interaction energies for v₃(CH₃F)=0 and 1 to the Morse/long-range(MLR) potential function for symmetry top impurity with atom model. These PESs fitting to 2340 points have root-mean-square(RMS) deviations of 0.07 cm^-1, and require only 167 parameters. Based on the analytical vibrationally averaged PESs, the rovibrational energy levels were calculated by employing Lanczos algorithm, with combined radial discrete variable representation and parity-adapted angular finite basis representation. Based on the wavefunction analysis and comparison of CH₃F-Ne with CH₃F-He and CH₃F-Ar complexes, the bound states were assigned. Spectral parameters for CH₃F-Rg(Rg:rare gas, Rg=He, Ne, Ar) complexes were fitted and discussed. Temperature dependent transition intensities for CH₃F-Ne were also reported and analyzed. The complete microwave and infrared spectra information for CH₃F-Ne made it possible to provide important guidance for future experimental spectroscopic assignments.     

Synthesis and characterization of new oligosilane derivatives of iron and molybdenum

By use of salt elimination, the transition metal substituted oligosilanes (η⁵-C₅Me₄Et)Fe(CO)₂SiMe₂SiMe₂Cl 1, (η⁵-C₅Me₄Et)Mo(CO)₃SiMe₂SiMe₂Br 2, (η⁵-C₅Me₄Et)Fe(CO)₂(SiMe₂)₆(CO)₂Fe(η⁵-C₅Me₄Et) 3 and (η⁵-C₅Me₄Et)Fe(CO)₂(SiMe₂)₆Br 4 were prepared and characterized. Compound 1 is well crystallized from pentane and its structure has been determined by X-ray diffraction analysis.     

Effect of fluorine substitution on the OH-radical-induced electron-transfer reaction in aqueous solutions of fluorinated alkyl iodides

The transient optical absorption bands formed at λ_max=340 and 435 nm, on reaction of ^√OH radicals in aerated acidic aqueous solutions of 1,1,1-trifluoro-2-iodoethane at low and high solute concentration, have been assigned to monomer and dimer radical cations, respectively. The deprotonation of the solute radical cations is the rate-determining step for the decay of the dimer radical cations. The stability constant for the dimer radical cation is determined to be 50 dm³ mol⁻¹ at 25°C. The dimer radical cation is a strong one-electron oxidant. Quantum chemical calculations and experimental results confirm that fluorine reduces the electron density at iodine and the ^√OH-radical-induced oxidation of fluoroiodoalkanes becomes a difficult process compared to iodoalkanes.     

Kinetics and mechanism of the gas phase reaction of Cl atoms with iodobenzene

Smog chamber/FTIR techniques were used to study the kinetics and mechanism of the reaction of Cl atoms with iodobenzene (C₆H₅I) in 20–700 Torr of N₂, air, or O₂ diluent at 296 K. The reaction proceeds with a rate constant k(Cl+C₆H₅I)=(3.3±0.7)×10⁻¹¹ cm³ molecule⁻¹ s⁻¹ to give chlorobenzene (C₆H₅Cl) in a yield which is indistinguishable from 100%. The title reaction proceeds via a displacement mechanism (probably addition followed by elimination).     

锗硅烯与CH3OH加成反应机理及区域选择性

采用密度泛函理论方法,在B3LYP/6-311++G(d, p)水平,研究了几种锗硅烯与CH₃OH的加成反应的微观机理和势能剖面,分析了锗硅烯中Si=Ge双键的极性对加成反应区域选择性的影响.研究结果表明,锗硅烯可分别与CH₃OH的单聚体或二聚体发生加成反应.所有加成反应均从初始亲核或亲电复合物的形成开始.母体锗硅烯H₂Si=GeH₂与CH₃OH二聚体的加成反应比其与CH₃OH单聚体的相应反应在动力学上更容易些,但在其它锗硅烯与CH₃OH的反应中情况则相反.用Ph或SiMe₃基团取代H₂Si=GeH₂中的H原子在动力学上使反应变得不利且SiMe₃基团的影响更显著.加成反应的区域选择性与锗硅烯中Si=Ge双键的极性以及Si-O(Ge-H)和Ge-O (Si-H)键的相对强弱都有关.     

Analysis of pπ → dπ bonding in halogen compounds of silicon, germanium and tin

Halogen lone pair ionization potentials for the main-group IV compounds MX₄ and MH₃Cl are corrected for the effects of potencial and relaxation energy using the corresponding halogen core binding energies. The corrected data indicate significant pπ --- dπ bonding in MX₄ (for M = Si, Ge and Sn), significant repulsion between the lone pairs and CH₃ group in CH₃Cl. and little or no pπ --- dπ bonding in SiH₃Cl and GeH₃Cl.     

Polymer chemistry. Part 1. Model compounds related to hexafluoropropenevinylidene fluoride elastomer

Model compounds related to the important elastomer derived from CH₂2=CF₂/CFCF₃ are synthesised from telomers (CF₃)₂CF(CH₂CF_2nI, by coupling and by fluorodeiodination reactions. These models, in reactions with bases, give information relating to mechanism of cross-linking of the polymer and indications of factors that limit its working life. Novel use of SbF₅ for dehydrofluorination in synthesis of fluorinated mono-enes and di-enes is described.     

Preparation of certain chloromethyl- and dichloromethyl-substituted chlorodisilanes and their behavior toward aluminum halides

Four new (chloromethyl)disilanes, (ClCH₂)Cl₂SiSiCl₂Me (I), (Cl₂CH)Cl₂SiSiCl₂Me(II), (ClCH₂)MeClSiSiClMe₂(III) and (ClCH₂)Me₂SiSiCl₃(IV), have been prepared and studied as to their attitude toward intramolecular rearrangement with aluminum chloride. The reactivity decreases in the order: (III) > (IV) > (II) (I). Similar reactivity to rearrangement of Me₃SiSiMe₂(CH₂Br)(V), ClMe₂SiSiMe₂(CH₂Br) (VI) and Me₃SiSiMeCl(CH₂Br) (VII) in the presence of aluminum bromide has been found to decrease in the order: (V) > (VI) > (VII). The results are discussed in terms of a mechanism favoring initial rate-determining step of ionization of the carbon-halogen bond in which the migrating group plays a minor role, if any, followed by migration of a silyl group from silicon to carbon. Disilanes (I) and (II) enter into the Friedel-Crafts reaction with benzene to give, after methylation, PhCH₂SiMe₂SiMe₃ and Ph₂CHSiMe₂SiMe₃, respectively.