摘要:

AbstractCondensation and crosslinking reactions of furfuryl alcohol (FA) and FA with tris (2‐hydroxyethyl )isocyanurate (THEIC) are studied by means of DSC, TG, TBA, NMR and elemental analysis. Four exothermic peaks are observed on the DSC curves of thermal condensation of FA and FA with THEIC in the presence of sulfuric acid. The peaks I, II (50–80°C), III (110–130°C) and IV (150–190°C) correspond to linear polycondensation of FA through head‐to‐tail condensation, head‐to‐head etherification, crosslinking dehydration reaction between methylene group and terminal hydroxy group of FA polymeric chain and to further crosslinking reaction at higher temperature, respectively. The reactivity of FA and THEIC increases sharply at 130–150°C and THEIC is reacted completely at 150°C. Addition of THEIC raises the initial decomposition temperature

ISSN:1001-604X    

DOI:10.1002/cjoc.19910090301

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA, Weinheim    

年代:1991

数据来源: WILEY

摘要:

AbstractYttrium forms with CPApM a 1:2 α‐complex instantaneously in acidic medium. At pH∼5 (buffer solution), the α‐complex is transformed to a β‐complex with an absorption peak at 755 nm after standing. The transformation reaction is a first‐order reaction. The rate constant and the apparent activation energy were found to be 9.67 × 10−1min−1and 52.3 kJ·mol−1respectively. The mechanism of the reaction shows that the β‐complex (Y:CPApM=2:4) is formed by combining two molecules of α‐complex with th

ISSN:1001-604X    

DOI:10.1002/cjoc.19910090302

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA, Weinheim    

年代:1991

数据来源: WILEY

摘要:

AbstractESR method was used to elucidate the mechanism of the reactions of alkyl, allyl or benzyl halides with dicyclopentadienyldicarbonyl titanium. The paramagnetic [intermediates of the reactions were identified during the course of the reactions. The reaction mechanism based on ESR findings and the products analyses is postulated to operate on radical pathways. When alkyl halides were used to react with the organometallic compound 1, the intermediate found was [Cp2Ti(CO)X] (C), and the main product was identified to be dicyclopentadienyl‐acyl‐halo titanium (3), an insertion of TiCO into R‐X,i.e.[Cp2Ti‐C(0)R] X. When allyl or benzyl halides were used, the intermediate found was [Cp2TiX] (B), and the main products were identified to be the dicyclopentadienyl titanium dihalides and the coupling products of allyl or benzyl

ISSN:1001-604X    

DOI:10.1002/cjoc.19910090303

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA, Weinheim    

年代:1991

数据来源: WILEY

摘要:

AbstractThe13C NMR study of the interaction between the trivalent lanthanide ions (from Dy to Lu) andD‐pantothenic acid in aqueous solution was presented. The unambiguous resonance assignments were made on the basis of pH dependence and the analysis of molecular geometry.13C paramagnetic shifts were separated into the contact and dipolar components by Reilley's method. The complex stability constant is 12.0 L / mol for the 1:1 ytterbium complex. An analysis of the shift data shows that heavy lanthanide ions form isostructural complexes with the substrate and the hyperfine coupling constant is independent of the ions used in the study.D‐pantothenic acid is coordinated to the metal via the two oxygens of the carboxyl group with 2.25Å of Ln—O distances. The electron spin density distribution and the structural details of the complex were elucidated from the shift data. It is stated that contact contributions, while small for nuclei of several bonds away from the metal, should not be dismisseda

ISSN:1001-604X    

DOI:10.1002/cjoc.19910090304

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA, Weinheim    

年代:1991

数据来源: WILEY

摘要:

AbstractA computer‐assisted method is presented for optimization of multicomponent solvent mobile phase selection for separation ofO‐ethyl‐N‐isopropyl phosphoro (thioureido) thioates in reversed‐phase HPLC and four geometric isomers of pesticides Decis in normal‐phase HPLC. The method is based on Snyder's solvent selection triangle concept using a statistical method. The optimization of the separation over the experimental region is based on a special polynomial estimation from seven experimental runs, and resolution (Rs) is used as the selection criterion. Excellent agreement was obtained between predicted data and experimen

ISSN:1001-604X    

DOI:10.1002/cjoc.19910090305

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA, Weinheim    

年代:1991

数据来源: WILEY

摘要:

AbstractIn this paper, the concept of reversed‐ or normal‐phase chiral stationary phase liquid chromatography has been put forward according to the polar strength of mobile and stationary phases. The statistical model developed in HPLC has been used to investigate the separation mechanism ofD‐ andL‐enantiomer in chiral stationary phase liquid chromatography. It has been observed that the variation of capacity factor of enantiomers with mobile phase composition in both reversed‐phase and normal‐phase chiral stationary phase liquid chromatography can be described by the fundamental elution equation lnk' =a+blnCb+cCb. The effect of mobile phase composition on the selectivity of enantiomersDandLin normal‐phase chiral stationary phase liquid chromatography can be described by the equation lnα =Δa+ΔblnCb, but in reversed‐phase chiral stationary phase liquid chromatography the selectivity is almost independant of the mobile

ISSN:1001-604X    

DOI:10.1002/cjoc.19910090306

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA, Weinheim    

年代:1991

数据来源: WILEY

摘要:

AbstractThe prediction of the peak width at half height is an important aspect in the optimization of the chromatographic operating conditions. In this paper, a linear relationship, between the peak widths at half height and the retention values with various isocratic elution is observed. In gradient elution, however, the relationship between the peak widths at half height and the so‐called invented retention values that correspond to the mobile phase composition by eluting the solute from the column end is developed. We believe that there is almost the same band width at half height inside the column (in unit of length) for different solutes. The peak width at half height in the chromatogram (in unit of time) is mainly determined by the capacity factor of the solute when it is eluted from the column end. The larger the capacity factor of a solute eluted from the column end, the more slowly will be the solute eluted from the column end and the wider will be the peak width at half height. It is possible to predict the peak width at half height in various isocratic and gradient elutions by using this linear relationshi

ISSN:1001-604X    

DOI:10.1002/cjoc.19910090307

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA, Weinheim    

年代:1991

数据来源: WILEY

摘要:

AbstractSolid state13C NMR spectra of a series of naphthol‐1 and naphthol‐2‐arylazo‐derivatives were studied and compared with respective results in solutions. Signals of carbon nuclei of naphthalene ring were assigned. Tautomeric forms of compounds were determined. It was shown that 4‐(p‐NO2C6H4)‐azonaphthol‐1 and 1‐(p‐NO2C6H4)‐azonaphthol‐2 in solid state existed exclusively in quinohydrazone form. The other two compounds—1‐(C6F5)‐azonaphthol‐2 and 2‐(p‐CH2C6H4)‐azonaphthol‐1 in solid state were not found in the form of individual tautomeric mixtures but in respective tautomeric equilibrium form. Thus, during transition from liquid to solid state, the tautomeric equilibrium was practically unchanged. In solid state it was found that rotation around aryl‐N bond was hinde

ISSN:1001-604X    

DOI:10.1002/cjoc.19910090308

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA, Weinheim    

年代:1991

数据来源: WILEY

摘要:

AbstractC‐Alkylation of some α‐acylamino ketones were achieved with alkyl halides by means of sodium ethoxide in ethanol. The present paper deals with theC‐alkylation ofN,N‐diformylamino ketones and the difference in stability of the ami

ISSN:1001-604X    

DOI:10.1002/cjoc.19910090309

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA, Weinheim    

年代:1991

数据来源: WILEY

摘要:

AbstractSix fulgides of indole series are prepared. Three of them are photochromic. The others in which R1is hydrogen atom do not show photochromism. OnlyZ‐Eisomerizations occur on irradiation at 365 nm. The effects of molecular structural modifications on photochromic properties are also discusse

ISSN:1001-604X    

DOI:10.1002/cjoc.19910090310

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA, Weinheim    

年代:1991

数据来源: WILEY