某些全卤代氟氯烷与硫酚钠的自发反应——-苯硫基阴离子对氯原子的进攻

全卤代的氟氯烷以其化学稳定性著称。在实验室中,氟利昂-113通常不是用作反应试剂而是作为惰性溶剂来使用。迄今,除了氟氯烷与某些金属和路易斯酸等的反应外,其他类型的反应研究得很少。全氟和多氟型氟卤烷难以进行碳原子上的S_N2取代,因而在与亲核试剂的反应中,卤素原子便成为亲核进攻对象。氟卤烷中的溴原子受亲核试剂进攻的例子已有报道,但氯原子是否也可受进攻则仍属未知。本文首次报道1,1,2-三氟三氯乙烷(1a),1,1,1-三氟三氯乙烷(1b)和1,1-二氟四氯乙烷(1c)与硫酚钠在室温下反应生成相应的苯硫基取代氟氯烃的研究结果。     

The reaction of thiophenoxide with amino-substituted chloro-cyclotriphosphazenes

In the present work, a series of aminocyclotriphosphazene containing sulfur group compounds have been synthesised and characterised by elemental analysis, mass (MS), ¹H and ³¹P NMR spectroscopies. The formation of thiophenoxy-substituted aminocyclotriphosphazenes could be explained by different mechanisms based on primary or secondary amino-substituted cyclotriphosphazenes. Compounds 3, 5 and 7 could be formed by a proton abstraction-chloride elimination and 9, 11 and 13 may be constituted both the S_N² and S_N¹ reaction mechanisms, respectively. These mechanisms are supported by the crystal structures of 5 and 13. Molecular and crystal structures of 5 and 13 have been characterised by X-ray crystallography. The structures of 5 and 13 are monoclinic and have space groups P2₁/n.     

Slow photoelectron velocity-map imaging spectroscopy of the phenoxide and thiophenoxide anions

High resolution anion photodetachment spectra of the phenoxide and thiophenoxide anions were obtained with slow electron velocity-map imaging. The spectra show transitions to the X(2)B(1) neutral states of both species and to the ?(2)B(2) state of the thiophenoxy radical. Comparison of the spectra with Franck-Condon simulations allows several gas-phase vibrations to be assigned. The adiabatic electron affinities are determined to be 2.2538(8) eV and 2.3542(6) eV for phenoxy and thiophenoxy, respectively. The term energy of the ?(2)B(2) state of thiophenoxy is found to be 0.3719(9) eV, higher than the values reported in photodissociation experiments of thiophenol.     

Micellar catalysis of the reaction of 2,4-dinitrofluorobenzene with phenoxide and thiophenoxide ions

The reactions of 2,4-dinitrofluorobenzene with phenoxide and thiophenoxide ion in water are strongly catalyzed by micelles of cetyltrimethylammonium bromide (CTABr) by factors of 230 and 1100 respectively. Nonionic micelles of Brij weakly catalyze the reaction with thiophenoxide ion. Spectral measurements show that phenoxide, and especially thiophenoxide, ions interact strongly with micelles of CTABr which also markedly change the acid dissociation of phenol under given buffer conditions.     

Reactions of triethylsilyl thiophenoxide with ketones having an electron-with-drawing group on the α-carbon

Triethylsilyl thiophenoxide has been found to react with easily enolizable ketones to give silyl enol ethers; these have also been synthesized by a Rh^I complex catalysed reaction of triethylsilane with enolizable ketones in the presence of a small amount of silyl thioether or thiophenol.     

Halophilic reactions of nucleophiles: 2. Crown ether promoted reactions of dibromodifluoromethane and sodium thiophenoxide1

In ether and benzene, CF₂Br₂ reacts with PhSNa either very slowly or not at all. However, catalytic amounts of dibenzo-18-crown-6 can accelerate the reactions dramatically, and more notably, the desired product PhSCF₂Br (1) can be obtained in high yield, whereas the formation of the by-products PhSSPh (2) and PhSCF₂H (3) is significantly suppressed. In ethereal solution containing 2.8 × 10^?3 M of the crown ether, ranges of the yields of 1, 2, and 3 were 78–85%, 5–10%, and 1–2%, respectively. These results represent significant improvements over those most recently reported. Possible reaction pathways were discussed and new evidence for an anionic chain mechanism is presented, e.g.: (1) Moisture and other proton-donating species retard the desired reaction but increase the yields of 2 and 3. (2) Protium-donating solvents, light, oxygen and di-tert-butyl nitroxide do not affect the reactions significantly. (3) With CCl₄ as the solvent, PhSCF₂Cl, BrCCl₃ and HCCl₃ were also formed, but not CCl₃-CCl₃. Evidently, PhSCF₂Cl was formed from a chlorophilic attack by PhSCF₂^? on solvent molecules.     

Thiophene series. XV The effect of leaving groups on the reactivity of nitro-activated thiophene derivatives with sodium thiophenoxide

The effect of leaving groups on the reactivity of 3-X-2-nitrothiophene (1), 2-X-3-nitrothiophene (II) and 2-X-5-nitrothiophene (III) (X = Cl, Br, I, OC₆H₄NO₂(p), SO₂C₆ H₅) with sodium thiophenoxide has been examined. The results show that the reactivity ratio kIII/kII is always greater than unity and is relatively uninfluenced by changing leaving groups compared to the ratio kI/kII. The ratio kI/kII is greater or smaller than unity, according to following patterns of leaving groups Examination of the reactivity of the three series of compounds having Cl, Br, I and C₆H₄NO₂(p) as leaving groups showed the absence of an “element effect” which indicates that in the transition states of these displacement reactions there is little breaking of the bond to the group being displaced.     

Reactivity of 2-fluoro-5-nitrothiophene towards sodium thiophenoxide and piperidine. Comparison with other 2-halogeno-5-nitrothiophenes

2-Fluoro-5-nitrothiophene reacts with sodium thiophenoxide and piperidine much faster than other 2-halogeno-5-nitrothiophenes. In methanol the reactions with both nucleophiles follow overall second order kinetics, while in benzene the observed second order rate constants of the reaction with piperidine show a linear dependence by the piperidine concentration. Such a dependence, which is mild for the chloro, bromo and iodo derivative, becomes strong for the fluoro compound. Moreover, the reaction of 2-fluoro-5-nitrothiophene with [1-²H]piperidine shows the absence of a primary isotope effect. The results are interpreted within the framework of the two-stage, intermediate-complex mechanism, the first stage (attack of the nucleophile on the substrate) being rate determing for the reactions of 2-fluoro-, -chloro-, -bromo- and -iodo-5-nitrothiophene with thiophenoxide in methanol and of 2-chloro-, -bromo- and -iodo-5-nitrothiophene with piperidine in benzene. In the case of the reaction of 2-fluoro-5-nitrothiophene with piperidine in benzene the data are in agreement with a mechanism in which the rate determining step is the decomposition of the tetrahedral intermediate into products. The intervention of a second amine molecule in the transition state of the rate determining step can be rationalized in terms of bifunctional catalysis. A comparison of reactivity of thiophenoxide and piperidine towards 2-halogeno-5-nitrothiophenes (Hal = F, Cl, Br, I) indicates a greater sensitivity of the reaction with piperidine than that with thiophenoxide to the change of the leaving group.     

Ring-closure reactions through intramolecular substitution of thiophenoxide by oxygen and nitrogen nucleophiles: simple stereospecific synthesis of 4,5-dihydroisoxazoles and 4,5-dihydropyrazoles

A new and simple method for the stereospecific synthesis of 3,5-disubstituted-4,5-dihydro-isoxazoles (chiral isoxazolines) from readily available oximes of chiral Michael adducts of thiophenol to chalcones is reported. An analogous reaction with the N-arylhydrazones of the Michael adduct gave nonracemic 1-(aryl)-3,5-diphenyl-4,5-dihydro-1H-pyrazoles (chiral pyrazolines), but these products are configurationally unstable. The key step of the synthesis is the ring-closure reaction, which occurs by a stereospecific intramoleculer nucleophilic substitution of thiophenoxide.     

The effect of inert salts on the structure of the transition state in the SN2 reaction between thiophenoxide ion and butyl chloride

The effect of inert salts on the structure of the transition state has been determined by measuring the secondary alpha deuterium and the chlorine leaving group kinetic isotope effects for the S(N)2 reaction between n-butyl chloride and thiophenoxide ion in both methanol and DMSO. The smaller secondary alpha deuterium isotope effects and very slightly larger chlorine isotope effects found in both solvents when the inert salt is present suggests that the S(N)2 transition state is tighter and more product-like, with a shorter S-C(alpha) and very a slightly longer C(alpha)-Cl bond when the added salt is present. The salt effect on the reaction in methanol where the reacting nucleophile is the solvent-separated ion-pair complex is much greater than the salt effect on the reaction in DMSO where the reacting nucleophile is the free ion. This greater change in transition-state structure found when the inert salt is present in methanol is consistent with the solvation rule for S(N)2 reactions. The greater change in the S-C(alpha) bond is predicted by the bond strength hypothesis. A rationale for the changes found in transition-state structure when the inert salt is present is suggested for both the free-ion and the ion-pair reactions.     

利用手持技术改进测定乙醇分子结构实验

利用压强传感器代替排水集气法,改进测定乙醇分子结构实验的仪器装置,并探索最佳反应条件。另外,设计两个空白实验,结合压强变化曲线对实验误差进行相关讨论。     

光谱仪测试范围的扩展

由于石化行业的生产需要，其材质的使用具有多样性和广泛性，经常会出现顾客委托的测试样品的一个或几个元素跨越光谱仪现有测试程序测量范围的情况。本法通过对光谱仪测试原理的认识，根据光谱仪的测试能力及标样的采集，实现了一个或几个元素测量范围的扩展，并对其测量的影响因素进行了研究。     

Neutral diterpenoids of oleoresins of five species of conifers of Transcarpathia

The compositions of the neutral diterpenoids of the oleoresins of five species of conifers growing in the Transcarpathia have been studied. It has been found that the oleoresins ofAbies alba M.,Larix decidua M., andPicea excelsa L. contain more than 50% of neutral diterpenoids. The group and qualitative compositions of the oxygen-containing diterpenoids have been determined. In the oleoresins ofAbies alba,Picea excelsa, andPicea abies tertiary alcohols — cis-abienol and isocembrol — predominate, while inLarix decidua the main component is the hydroxy ester larixyl acetate. Primary alcohols related to the resin acids have been found in all the oleoresins investigated. Features of the distribution of diterpenoids according to the species of conifers have been revealed. The results obtained are necessary for the chemotaxonomy of conifers of the family Pinceae.Novosibirsk Institute of Organic Chemistry, Siberian Branch, Academy of Sciences of the USSR. Translated from Khimiya Prirodynkh Soedinenii, No. 6, pp. 812–816, November–December, 1988.     

Dichroism of absorption and polarization of phosphorescence of molecules of the closed form of nitrobenzospirothiopyran

The spectral-polarization characteristics of absorption and phosphorescence of molecules of the initial form of nitro-substituted indolinospirobenzothiopyran were studied in oriented polyethylene films and in solutions with different polarity. An oscillator model of the electron transitions responsible for the formation of absorption and luminescence spectra was suggested. It was established that the principal differences in the spectral and photophysical properties of the compound studied and its oxygen-containing analog are associated with the fact that the electronegativity of the S atom is lower than that of the O atom. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1143–1146, June, 1997.     

Influence of viscosity of medium on processes of oxygen quenching of excited states of mesoporphyrin

The oxygen quenching rate constants for singlet and triplet excited states of the dimethyl ester of mesoporphyrin IX increase with decreasing viscosity of the medium and reach a maximum at a viscosity of approximately 0.4 mPa·sec, after which the rate constants begin to decrease. The drop in rate constant with increasing fluidity of the medium may be related to a nonequilibrium character of the elementary act in the interaction of the reactants in the solvent cage. In viscous media such as isopropyl alcohol, isobutyl alcohol, and isoamyl alcohol, the reaction radius is greater than the sum of the radii of the reacting particles. The long-range character of these processes is due to the relatively weak dependence of the quenching probability on distance.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 25, No. 2, pp. 161–167, March–April, 1989.     

Determination of heats of detonation and influence of components of composite explosives on heats of detonation of high explosives

The heats of detonation of 20 simple high explosives and explosive mixtures were determined by means of an adiabatic detonation calorimeter designed by the authors. The results indicated that the performance of the instrument was reliable and the experimental data were very accurate. For explosive mixtures, there was a linear accumulative relationship between the heats of detonation of the explosive mixture and its components. Accordingly, the heats of detonation of explosive mixtures could be calculated directly from the heats of detonation of simple explosives and the characteristic heats of other components. The experiments showed that the gold or brass shell of the cylindrical charge could be substituted by a thick-walled porcelain shell, which had the advantage of cheapness.

     

物质分配系数的测定实验改进

实验教学目的是从解决实际问题出发,以实验技术训练和实验设计思想培养为目标。介绍了将单一的物质分配系数测定实验改进为综合实验,提高了实验效果及实验资源利用率。