Theoretical study of the unimolecular decomposition mechanisms of energetic TNAD and TNAZ explosives

Calculation methods based on hybrid Density Functional Theory (DFT) with the basis sets of the B3LYP/6‐31+G(d)//B3LYP/4‐31G(d) method and the differential overlap (INDO) program were used to derive reasonable decomposition mechanisms of 1,4,5,8‐tetranitro‐1,4,5,8‐tetraazadecalin (TNAD) and 1,3,3‐trinitroazetidine (TNAZ) explosives. All possible decomposition species and transition states, including intermediates and products, were identified and their corresponding enthalpy of formation and Gibbs free energy of formation were obtained using polyparametric modification equations. INDO bond energy calculation results reveal the weakest bonding site for reference and determine where cleavage can occur easily. This work is concerned mainly with eliminating HONO (cis or trans form). The activation energy for trans‐form HONO elimination is lower than that of cis‐form HONO elimination in the initial steps of both TNAD and TNAZ decomposition, being 18.5 kJ/mol and 33.3 kJ/mol, respectively. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2005     

Stereochemical effects in mass spectrometry. Part 10-reaction mass spectrometry of cyclic glycols and monosaccharides with methylene chloride as reagent gas

The reaction mass spectrometry of cyclic glycols and monosaccharides with methylene chloride as reagent was studied. In the presence of ammonia, it was found that methylene chloride reacted stereoselectively with the quasi-molecular ions of cyclic glycols and monosaccharides to form characteristic ions, by comparison of the relative abundances of which the stereoisomers of cyclopentane-l,2-diols and cyclohexane-l,2-diols and some monosaccharides could be definitely distinguished.     

配合物稳定性与配体酸碱强度之间的直线自由能关系 XIII. N-(间位取代苯基)氨基乙酸，邻菲啰啉(α,'α-联吡啶)与镍(II),钴(II)和锌(II)生成三元配合物的稳定性研究

The formation constants of ternary mixed ligand complex compounds (logK_(MAB~(MA)) formed from 1,10-phenanthroline or 2,2'-bipyridyl (A), N-(meta-substituted phenyl) glycines, (B, m-RphG, R=CH_3, H, CH_3O, Cl) with Nickel(Ⅱ), Cobalt(Ⅱ) and Zinc(Ⅱ) were determined by pH method at 25 ℃ in 30% (Volume) ethanol solution in presence of 0.1 mol·dm~(-3) NaClO_4 or 0.1 mol·dm~(-3) KNO_3. It was found that linear free energy relationships exist between the stability of ternary complex compounds and the base strengths of ligands in all six ternary systems investigated. The stability of the ternary complex compounds was discused in terms of ΔlogK_M values and HSAB theory. It was found that linear relationships also exist between ΔlogK_M and pK_2 in the Ni(II)-phen-m-RPhG ternary system.     

芳香族重氮盐氧化还原引发体系的研究——Ⅲ.芳香族重氮盐与亚铁盐氧化还原引发丙烯腈聚合过程中微量铜离子的影响

以苯重氮硼氟酸盐与亚铁盐在微量铜离子存在时能引发丙烯腈聚合,聚合速率服从:R∝[φN_2~+]~(1/2)[Fe~(++)]~(1/4)[Cu~(++)]~(1/4),氧化还原引发历程为: Fe~(++)+Cu~(++) Fe~(+++)+Cu~+ φN_2~++Cu~+→φ·+N_2+Cu~(++) φ·+M→φM·→φMM·…该历程符合上述动力学关系。但使用对硝基苯重氮硼氟酸盐时,微量铜离子对聚合反应速率影响不大,与亚铁盐浓度在一定范围呈R∝[Fe~(++)]~(1/2)的关系,因此例的引发历程为: φN_2~++Fe~(++)→φ·+N_2+Fe~(+++) φ·+M→φM·→φMM·…苯环上推电子取代基降低了重氮基的氧化势,如对位取代甲氧基、甲基或没有取代基都不能用纯亚铁盐引发丙烯腈聚合,需有微量铜盐存在才能聚合。而拉电子取代基如对位取代硝基、羧基可用纯亚铁盐引发聚合。     

Molecular simulation of surfactant-assisted protein refolding

Protein refolding to its native state in vitro is a challenging problem in biotechnology, i.e., in the biomedical, pharmaceutical, and food industry. Protein aggregation and misfolding usually inhibit the recovery of proteins with their native states. These problems can be partially solved by adding a surfactant into a suitable solution environment. However, the process of this surfactant-assisted protein refolding is not well understood. In this paper, we wish to report on the first-ever simulations of surfactant-assisted protein refolding. For these studies, we defined a simple model for the protein and the surfactant and investigated how a surfactant affected the folding behavior of a two-dimensional lattice protein molecule. The model protein and model surfactant were chosen such that we could capture the important features of the folding process and the interaction between the protein and the surfactant, namely, the hydrophobic interaction. It was shown that, in the absence of surfactants, a protein in an "energy trap" conformation, i.e., a local energy minima, could not fold into the native form, which was characterized by a global energy minimum. The addition of surfactants created folding pathways via the formation of protein-surfactant complexes and thus enabled the conformations that fell into energy trap states to escape from these traps and to form the native proteins. The simulation results also showed that it was necessary to match the hydrophobicity of surfactant to the concentration of denaturant, which was added to control the folding or unfolding of a protein. The surfactants with different hydrophobicity had their own concentration range on assisting protein refolding. All of these simulations agreed well with experimental results reported elsewhere, indicating both the validity of the simulations presented here and the potential application of the simulations for the design of a surfactant on assisting protein refolding.     

Novel construction of the brassinolide side chain

A stereoselective synthesis of brassinolide, which involves construction of the side chain by a highly stereoselective aldol reaction between 20S-6β-methoxy-3α,5-cyclo-5α-pregnane-20-carboxaldehyde 2 and ketone 3 or 4 catalyzed by l-proline, is described.     

Acidichromism in the Mixed Langmuir—Blodgett Films of Stearic Acid with a Carbazole—containing Schiff Base

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Studies of the electrochemical behavior of epinephrine at a homocysteine self-assembled electrode

The self-assembled electrode with the homocysteine monolayer (Hcy/Au) has been characterized by infrared spectroscopy and ac impedance spectroscopy in electrolyte. The Hcy/Au electrode is demonstrated to promote the electrochemical response of epinephrine (E) by cyclic voltammetry. A pair of well-defined redox waves was obtained and the calculated standard rate constant (k_s) is 2.1×10⁻² cm s⁻¹ at the self-assembled electrode. The reduction peak of E can be used to determine the concentration of E in presence of ascorbic acid (AA) owing to the Hcy/Au also promoting the electrochemical oxidation of AA.