HPLC检定二氨基甲苯参考物质纯度的研究

应用高效液相色谱法研究分离2,6—、2,4—、2,3—和3,4—二氨基甲苯异构体的色谱系统条件和检定二氨基甲苯参考物质纯度的试验方法     

Ab Initio studies on the rotational equilibria of 2-substituted furan and thiophene carbonyl derivatives

Summary The relative stabilities of syn- and anti-isomers of 2-substituted furan and thiophene carbonyl derivatives are investigated by theab initio MO method. The energy differences between the rotamers are 1–3 kcal mol^–1 but the barriers to rotation are ca. 10 kcal mol^–1 so that free rotational mode is predicted to be a rather difficult process. Application of the self-consistent reaction field (SCRF) method to account for the solvent effect indicates that the isomer with a higher dipole moment (syn) is favored in solution. An electron withdrawing 2-substituent favors syn-isomers for furan carbonyls in contrast to thiophene carbonyls for which anti-isomers are favored. These trends are ascribable to a decrease in electrostatic repulsive and attractive interactions, respectively, in the syn forms of furan and thiophene carbonyls. Contribution of non-bonded repulsive interaction in the anti-isomer is important for the relative stability of the syn-isomer of furan carbonyl derivative. Solvent effects due to higher dielectric continuum are small on the absolute values of energy differences but can reverse the order of stability of the two isomers due to a greater stability acquired by an isomer (syn) with higher dipole moment in solution. The major factor determining stability, or instability, of syn-isomer is a repulsive electrostatic interaction between the two oxygen atoms for furan carbonyls and an attractive electrostatic interaction between the sulfur and oxygen atoms for thiophene carbonyls.     

用硫酸酯酶进行α－和β－萘酚的分离

用硫酸酯酶进行α－和β－萘酚的分离姜忠义，陈洪钫（天津大学化工系天津３０００７２）关键词硫酸酯酶，萘酚，异构体，分离，反应机理萘酚有α－和β－两种异构体，两者均为重要的有机原料和染料中间体，但又各有专门用途，须将其分离［１］．传统的分离方法条件苛刻、...     

Inorganic Benzene Valence Isomers

It has been computationally proposed that there are more than 200 possible isomeric structures for the C₆H₆ molecule, among which benzene (CH)₆ represents the most thermodynamically stable molecule and its chemistry has been extensively developed. Three benzene valence isomers (CR)₆, namely, prismane, Dewar benzene, and benzvalene, have also been synthesized to date. Incorporation of heteroatoms in the skeletal frameworks allows access to inorganic analogues of benzene and its valence isomers, which have attracted considerable attention due to their peculiar structural and electronic features. Experimentally, more than 30 examples of inorganic benzene and its valence isomers have been developed and characterized so far. In this contribution, their synthesis and characterization, as well as their stability and chemical properties, are discussed.     

Half-lives of ground and isomeric states in Cd and the astrophysical origin of Ru

First experimental evidence for a high-spin isomer (25/²⁺$25/2^{+}$) in ⁹⁷Cd, a waiting point in the astrophysical rapid proton capture process, is presented. The data were obtained in β-decay studies at NSCL using the new RF Fragment Separator system and detecting β-delayed protons and β-delayed γ rays. Decays from ground and isomeric states were disentangled, and proton emission branches were determined for the first time. We find half-lives of 1.10(8) s and 3.8(2) s, and β-delayed proton emission branches of 12(2)% and 25(4)% were deduced for the ground and isomeric states, respectively. With these results, the nuclear data needed to determine an rp-process contribution to the unknown origin of solar ⁹⁶Ru are in place. When the new data are included in astrophysical rp-process calculations, one finds that an rp-process origin of ⁹⁶Ru is unlikely.     

Prediction of Redox Potentials and Isomer Distribution Yields for Reductive Dechlorination of Chlorobenzenes

Abstract

Gibbs free energies of reductive dechlorination processes of chlorobenzenes are calculated from thermodynamic data. The results are utilized to predict redox potentials and isomer distribution yields.

The model predicts a standard redox potential of 0.680 V for the reduction of hexachlorobenzene to pentachlorobenzene, tapering off to 0.535 V for the reduction of monochlorobenzene to benzene. It is shown that under anaerobic conditions, reductive dechlorination is more likely to occur, while aerobic conditions favour the formation of chlorophenols.

An isomer distribution yield is predicted for each of the reductive dechlorination processes of chlorobenzenes. Predicted yields correspond to experimental values within 10%. The model includes a possibility to establish a temperature dependence of the relative isomer yields.     

Accelerator Disaster Scenarios, the Unabomber, and Scientific Risks

The possibility that experiments at high-energy accelerators could create new forms of matter that would ultimately destroy the Earth has been considered several times in the past quarter century. One consequence of the earliest of these disaster scenarios was that the authors of a 1993 article in Physics Today who reviewed the experiments that had been carried out at the Bevalac at Lawrence Berkeley Laboratory were placed on the FBI’s Unabomber watch list. Later, concerns that experiments at the Relativistic Heavy Ion Collider at Brookhaven National Laboratory might create mini black holes or nuggets of stable strange quark matter resulted in a flurry of articles in the popular press. I discuss this history, as well as Richard A. Posner’s provocative analysis and recommendations on how to deal with such scientific risks. I conclude that better communication between scientists and nonscientists would serve to assuage unreasonable fears and focus attention on truly serious potential threats to humankind. Joseph I. Kapusta: Joseph I. Kapusta received his Ph.D. degree at the University of California at Berkeley in 1978 and has been on the faculty of the School of Physics and Astronomy at the University of Minnesota since 1982. He is the author of over 150 papers in refereed journals and conference proceedings and of Finite Temperature Field Theory (Cambridge University Press, 1989; second edition with Charles Gale, 2006).     

对环芳烷二氯化产物组成的GC-MS表征

对环芳烷([2,2]Paracyclophane,简称PCP）是指苯环对位桥联的化合物,PCP及其氯代PCP的重要用途是通过升华、裂解、聚合等步骤沉积于物体表面形成聚合膜,该聚合膜具有透湿和透气小、抗化学腐蚀和抗辐射等优良性能[1,2].