（E）－2－甲基－1，3－戊二烯的振动光谱及其稳定构象的研究

记录了（Ｅ）－２－二甲基－１，３－戊二烯的固、液、气态ＦＴＩＲ光谱（４００～４０００ｃｍ~（－１））和固、液态Ｒａｍａｎ光谱（５０～４０００ｃｍ~（－１）），观测了６８５及６５８ｃｍ~（－１）谱线的变温ＦＴＩＲ光谱（－７３～１０℃）．对所得谱图进行的指认分析发现，该化合物存在两种单键旋转构象异构体ｓ－ｔｒａｎｓ和ｓ－ｃｉｓ，由变温ＦＴＩＲ光谱峰强度随温度的变化得到这两种构象互变的ΔＨ~０和ΔＳ~０。     

Molecular structure and conformational transitions of dichloroacetylchloride

RHF and MP2 techniques in 6–31G(d) basis set have been used to determine the structure of the isolated molecule CHCl₂COCl in two stable conformations (cis-and gosh-), as well as in transition states arising due to the rotary motion of CHCl₂ group around the C—C bond. The energy gap between the conformers and the relevant potential barriers has been calculated using the obtained potential dependence of the internal rotation. Plausible conformation of dichloroacetylchloride is discussed on the basis of ³⁵Cl NQR.     

S1←S0 Vibronic spectrum and structure of 2,2-difluoroethanal in the S1 state

The vibronic spectrum of the 2,2-difluoroethanal vapor was recorded using a multipass optical cell with an optical length of at least 140 m. The spectrum in the region of 300—364 nm was assigned to the S₁S₀ electronic transition (from the ground S₀ to the first excited singlet S₁ electronic state); the vibrational structure of the spectrum was analyzed. The spectrum bands were assigned to two systems of vibronic transitions, namely, transitions between the levels of the cis-conformer (S₀) and of the S₁ conformers, with the origins (0₀ ⁰ transitions between the zero vibrational levels of conformers) at 29192 and 29087 cm^–1, respectively. Analysis of the spectrum showed that the S₁S₀ electronic excitation of the cis-conformer was followed by rotation of the CHF₂ top and pyramidal distortion of the carbonyl fragment. A number of fundamental frequencies were found for S₁ conformers, in particular, torsion and inversion energy levels. The experimental data are in satisfactory agreement with the results of quantum-chemical calculations for the 2,2-difluoroethanal molecule in the S₀ and S₁ states.     

Conformations of dibenzylideneacetone: An IR spectroscopic study

The conformational analysis of dibenzylideneacetone has been carried out using IR spectroscopy. Appearance of a triplet C=O band is attributed to the coexistence of three conformers viz s-cis, cis, s-cis, trans and nonplanar s-trans, trans in contrast to the earlier findings which showed the existence of only two conformers. The relative proportions of the conformers are in the order s-cis, trans> nonplanar s-trans, trans> s-cis, cis in less polar solvents and nonplanar s-trans, trans> s-cis, trans> s-cis, cis in more polar solvents.     

Conformational polymorphism in thiophenyl substituted quinones and the disappearing NMR spectrum

The stepwise addition of thiophenol to benzoquinone gives thiophenylbenzoquinone (1b), 2,5-and 2,6-di-(thiophenyl)benzoquinone (2,3),2,3,6-tri(thiophenyl)benzoquinone (4) and 2,3,5,6-tetra(thiophenyl)benzoquinone. (5). Compounds1–4 can be crystallized, and the¹³C NMR spectra are readily interpreted. Compound5 could not be crystallized easily, and the NMR showed more than twice as many lines as the number of carbon atoms. Slow evaporation in an NMR tube produced three distinct crystals. X-ray analysis of two crystals (5a and5c) showed the compounds to be conformational polymorphs. Direct synthesis of5 from tetrachlorobenzoquinone and thiophenol yielded only conformer5a, and the¹³C NMR spectrum showed only the 6 lines expected for four equivalent phenyl substituents on benzoquinone. Subjecting5a to a variety of solvents, reagents and temperatures did not regenerate the original¹³C NMR spectrum. The crystal structures, conformations, and polymorphs are discussed.     

Conformational features of Cl3P=NC(CF3)3 and Cl3P=NCCl(CCl3)2 molecules according to results of non-empirical calculations

Non-empirical RHF/6-31G* and MP2/6-31G* quantum chemical methods are used to calculate the molecular structure of trichlorophosphazene compounds: Cl₃P=NC(CF₃)₃ (I) and Cl₃P=NCCl(CCl₃)₂ (II). The corresponding geometric parameters obtained from the calculations are compared with X-ray diffraction analysis data reported in the literature. Conformational differences between the molecules of I and II, previously found by X-ray diffraction in the crystals of these compounds, are confirmed by non-empirical calculations of the molecules in the free state. The features of their geometry caused by intramolecular interactions are discussed.     

基于邻苯二甲酰-L-丙氨酸配体的两例Cu(II)纯手性同质多晶配合物:合成与结构

合成了2例Cu（Ⅱ）的纯手性同质多晶[CuL₂（Phen）]（HL=邻苯二甲酰-L-丙氨酸,Phen=1,10-菲咯啉）,并对其进行了表征。X射线单晶衍射测定表明,邻苯二甲酰-L-丙氨酸在2例配合物中采取了相同的配位方式,Cu（Ⅱ）原子具有变形的八面体配位环境,分别和2个邻苯二甲酰-L-丙氨酸离子上的2个羧基氧原子,1个1,10-菲咯啉的2个氮原子配位。不同的是这2例同质多晶显示出不同的颜色,并且配合物1属于单斜晶系,C2空间群,配合物2属于正交晶系,P2₁2₁2₁空间群。配合物1通过π…π堆积作用形成一维链状结构,配合物2是简单小分子结构。此外,DFT理论研究表明,配合物1具有较低的能量,稳定性更高。     

CH3NO2和CH3ONO结构及互异化反应的理论研究

采用了B3LYP、MP2方法,详细地计算了硝基甲烷(CH3ONO)和亚硝基甲酯(CH3NO2)的稳定结构、能量和振动频率等,并分析了它们的相对稳定性和相互转换的机理.结构优化结果表明,CH3ONO有两种稳定的构象cis和trans,CH3NO2有一种稳定的结构.在B3LYP/6-31G(d,p)方法的基础上,作出了CH3ONO的能量随CH3O-NO单键旋转的变化曲线图,定性地讨论了CH3ONO可能存在的稳定构象以及两种稳定构象之间互异化的机理.研究了CH3NO2与CH3ONO之间互异化的反应机理,计算了该异化反应发生时几何结构的变化以及最小能量途径,确定了该互异化反应实际上是C-N键和C-O键的断裂或形成的一个过程.     

Advances in the combined application of enzymatic and physical treatments for reducing food allergenicity

Abstract

Enzymatic hydrolysis of allergenic food proteins (betalactoglobulin, ovalbumin) was carried out during treatment at different combinations of time, pressure and temperature, with the aim of hydrolyzing the protein conformers transiently formed in the course of physical treatment in conditions where no irreversible modification of the target protein occurs. The amount of residual intact betalactoglobulin after 10min at 600 MPa in the presence of trypsin or chymotrypsin was found to decrease markedly with increasing temperature (30–44°C). The temperature sensitivity of the enzymatic hydrolysis of ovalbumin during similar treatments was much less pronounced than that of betalactoglobulin. The effects of temperature on the accessibility of betalactoglobulin conformers to proteases were studied at higher temperatures (55-65°C), and indicated that complete hydrolysis of betalactoglobulin cannot be achieved in a short time in the absence of a pressure treatment. None of the hydrolysis products of either protein was immunoreactive in Western-blot immunoassays.