Reactivity of the 1,2-Diphenytethyl Radical in a Solvent Cage

The 1,2-diphcnylethyl radical and derivatives were generated from photolysis of tran-f-stilbene and its derivatives 1–13 with secondary amines as quenchers. The 1,2-diphenylelhyl radicals that escaped from the solvent cage were trapped by 2-methyl-2-nitrosopropane (MNP) and were detected by the HPLCEPR method. The yield of the spin adduct is greater for tertiary amines. The smaller yields of the spin adduct formed from secondary amines are ascribed to greater reactivities of the 1,2-diphenylethyl and dialkylamino radicals within the solvent cage.     

Spectrophotometric method for phosphine residue determination in coriander

Spectrophotometric method for the determination of phosphine (PH₃) residues in coriander has been developed based on the reaction of phosphine with silver nitrate in 2% aqueous isopropanol. The yellow chromophore formed has an absorption maximum at 430 nm and the linear relation between the absorbances at 430 nm and the concentration of PH₃ is obeyed in the range of 0.02 to 0.17 g. The method is sensitive with a detection limit of 0.008 g and can be applied for determination of 0.02 g/g residue in coriander. Recovery of added PH₃ from a closed system ranges from 96 to 101%.     

Osmotic and activity coefficients at 25°C for tetraalkylammonium bromides in deuterium oxide

Earlier work by Lindenbaum and Boyd has demonstrated the important role of hydrophobic interactions involving the water solvent in determining the osmotic coefficients and properties of aqueous solutions of the tetraalkylammonium halides. Osmotic coefficients of solutions of tetramethyl-, tetraethyl-, tetrapropyl-, and tetrabutylammonium bromides in the more highly structured solvent D₂O have now been determined by the gravimetric isopiestic method, using reference solutions of NaCl in D₂O. The data were fitted to the Rush-Johnson and Pitzer equations. Satisfactory agreement with the results for aqueous solutions at comparable concentrations indicates that the solution chemistry of these quaternary ammonium bromides is not highly dependent on the degree of structure of the pure solvents. Supplementary data for mixtures of Me₄NBr with Et₄NBr, Pr₄NBr, or Bu₄NBr in both H₂O and D₂O are consistent with this conclusion.On leave 1980–82 from Banaras Hindu University, India     

Recyclization of pyrimidinium salts into 1,2,4-triazole derivatives

The interaction of the iodomethylates of pyrimidinyl-2-acetic acid derivatives with monosubstituted hydrazines, in addition to the products of a Kost-Sagitullin rearrangement, leads also to N-substituted triazoles. The structure of the triazoles was demonstrated by NOESY NMR experiments. The structure of the reaction products was determined on the basis of the response observed in the spectra between the methyl group protons of the triazole ring and the spatially close proton of the substituent in position 1 and a conclusion was drawn on the direction of the primary attack of nucleophile in the recyclization process of the pyrimidinium salts into a 1,2,4-triazole. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1175–1179, August, 2007.     

主成分回归-紫外光度法同时测定食用香料麦芽酚和乙基麦芽酚

报道了一种快速、简便的同时测定食用香料麦芽酚、乙基麦芽酚光度法,方法基于在pH2.87的B R缓冲溶液中对麦芽酚和乙基麦芽酚两组分混合溶液进行光度测定,所得的重叠波谱数据用主成分回归法(PCR)、经典最小二乘法(CLS)和偏最小二乘法(PLS)等化学计量学方法进行处理,结果表明主成分回归法(PCR)的预报误差最小。对样品进行测定,获得了较好的定量分析结果。麦芽酚和乙基麦芽酚的线性范围均为1.0～20.0mg·L-1;检出限分别为0.4347和0 5589mg·L-1。     

LiMn2O4的湿法合成及锰的光度法测定研究

The LiMn₂O₄ spinel was prepared by wet method using Li₂CO₃， Mn(CH₃COO)₂·4H₂O and CO₂ as raw ma-terials. The products were measured by TG/DTA， XRD， IR. The results Showed that the sample calcined at 800℃ for 10h was well crystallized monophase product. The contents of Mn(Ⅲ) and Mn(Ⅳ) of LiMn₂O₄ spinel were determined simultaneously by spectrophotometric analysis with pyrophosphoric acid.     

0.6~T人体核磁共振成象及其图象的彩色化处理

在0.6~τ超导磁体人体核磁共振成象设备上获得了横断、矢状、冠状各种断层的成象。采用了直接两维傅里叶变换成象方法,应用了自旋回波脉冲序列。由于人体心脏跳动和呼吸运动会造成图象模糊而使用心电延迟触发及呼吸门控方法。作者用一种相位调制光密度分割的方法将原始黑白灰度表示的核磁共振成象进行彩色化处理。提高了原图象低密度梯度区的清晰度,为进行医学图象诊断及判读解译提供了方便度。山了光学系统图,解释了光学信息处理方法。由所处理的人体核磁共振成象图片可以看出,在低密度梯给区更易辨认。参考文献10种。     

Metal Oxide Thin Films Containing Au Nano-Particles Prepared with Gas Diffusion Method

Au particles dispersed thin metal oxide films were prepared from precursor films containing HAuCl₄ with H₂S gas diffusion method. HAuCl₄ was uniformly dissolved in the films as promoted by hydroxypropyl cellulose (HPC). The mechanism of the Au particle formation was studied. It was found that HAuCl₄ was converted directly to Au metal particles upon contacting with H₂S gas. Au particles generated by this method were characterized with small particle size, sharp size distribution and high volume fraction in the films. The surface plasma resonance absorption of Au particles shifted to longer wavelength when TiO₂ component was introduced in the matrix.     

Calculation of the proton affinities of polyfluorobenzenes and the activation energies for 1,2-hydrogen shifts in their carbocations

Isolated polyfluorobenzene (PFB) molecules and their protonated forms are investigated by the AM1 method with full geometry optimization. The proton affinities of PFB are estimated for different protonated positions. The proton affinity of PFB averaged over all isomers is shown to decrease monotonically as the number of fluorine atoms in the molecule increases. The relative populations of different isomers of arenonium ions (AI) formed by PFB protonation are determined. From the calculated data, the value of ⁺ for the F atom in theipso-position is estimated as 1.00. The activation energies of the 1,2-hydrogen shifts in AI are calculated. The dependences of the proton affinity and the activation energies of 1,2-hydrogen shifts on the number of halogen atoms are found to have distinct characters for PFB and polychlorobenzenes. The physical reasons for these difference are discussed.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 1878–1882, November, 1993.     

铬天青S共振光散射法测定脱氧核糖核酸

介绍在阳离子表面活性剂十六烷基三甲基溴化铵(CTMAB)存在下阴离子染料铬天青S(CAS)共振光散射(RLS)法测定脱氧核糖核酸(DNA)的方法。在pH=5．27的六次甲基四铵一盐酸缓冲溶液中，研究了CAS—CT-MAB—yDNA体系的RLS光谱特征、影响因素和最佳反应条件。在最佳条件下，体系的RLS强度增加值△I与yDNA的浓度在50～800μg／L和1000～2000μg／L呈线性关系，其线性回归方程分别为△I=0．48c 2．56和△I=0．14c 17．86，相关系数分别为0．9997和0．9991，检出限为4．3ng／mL。该方法简便、快速，应用于合成样品中yDNA的测定，测定结果的相对标准偏差为2．93％～4．71％，回收率为97．8％～105．2％。