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231.
232.
The performance of Fourier transform infrared spectroscopy (FT-IR) detection coupled to high-performance liquid chromatography for the analysis of C60 and C70 fullerenes was investigated. The isocratic separation method involved an octadecylsilane (ODS) column and an acetonitrile–toluene (1:1) mobile phase. The hyphenated system was designed with a split valve to control eluent volume leading to the FT-IR detector; this allowed for additional coupling of the liquid chromatograph to ultraviolet–visible detection. On-line FT-IR spectra of C60 and C70 were matched with standard off-line FT-IR spectra from the literature. In addition, with band chromatograms individual fullerenes can be identified using FT-IR active modes known specifically for each fullerene. Few changes to a pre-existing HPLC–UV method were necessary for the HPLC–FT-IR method, and there was no need for fraction collection to identify the fullerenes C60 and C70. 相似文献
233.
J. Epsztajn A. Bieniek J. A. Kowalska 《Monatshefte für Chemie / Chemical Monthly》1996,127(6-7):701-715
Summary The reaction of benzyl bromide withbis-(N- and C-ortho)-lithiated chloroanilides4,5, and6 has been examined. It has been found that in the case where the lithiated compound was derived frommeta-methoxyanilides, pre-addition of LiBr orTMEDA was required to achieve C-benzylation. These results were accounted for by the conversion of the usually formed dimer into a mixed dimer with the LiBr orTMEDA complex in which the C-lithium bond appears to be more accessible towards electrophiles. The practical synthesis of -benzylchlorobenzoic acids10,11, and12 was accomplishedvia ionic reductive cleavage (Et3SiH/TiCl4) of the corresponding phthalides18,19, and20. The acids10,11b, and11c afforded the corresponding anthrones, upon treatment with trifluoroacetic anhydride which were oxidized by chromium trioxide to the new chloroantraquinones21,22, and23.
Anwendung von Organolithium und verwandten Reagenzien in organischen Synthesen, 16. Mitt.: Synthesen mittels aromatischer Metallierung. Eine bequeme regiospezifische Umwandlung von Chlorbenzoesäuren in ihre Benzylderivate
Zusammenfassung Die Reaktion von Benzylbromid mit denbis-(N- und C-ortho)-lithiierten Chloraniliden4,5 und6 wurde untersucht. Im Falle lithiierter Verbindungen ausmeta-Methoxyaniliden ist die Zugabe von LiBr oderTMEDA während des Lithiierungsprozesses für die C-Benzylierung erforderlich. Diese Ergebnisse werden durch Umwandlung des gewöhnlich enstehenden Dimers in ein gemischtes Dimer mit dem LiBr- oderTMEDA-Komplex erklärt, in welchem die C-Li-Bindung für Elektrophile leichter zugänglich ist. Diese praktische Synthese dero-Benzylchlorbenzoesäuren10,11 und12 wird durch reduktive Spaltung der entsprechenden Phthalide18,19 und20 mit Et3SiH/TiCl4 ergänzt. Bei der Reaktion der Säuren10,11b und11c mit Trifluoressigsäureanhydrid entstehen die erwarteten Anthrone, die durch Oxidation mit Chromtrioxid in die neuen Chloranthrachinone21,22 und23 umgewandelt wurden.相似文献
234.
The comparison was made of the dissociation degree values for the hydrogen-bond multimers of two geometrical isomers: cis- and trans-9-octadecenoic acids. The measurements were performed for the series of solutions of the discussed substances in the inactive solvents: carbon tetrachloride and n-hexane. The applied technique was ir absorption spectroscopy. The general statement is that trans-9-octadecenoic acid in both carbon tetrachloride and n-hexane shows greater tendency towards dissociation of multimers than cis-9-octadeconoic acid. 相似文献
235.
Joanna Kowalska 《Tetrahedron letters》2007,48(31):5475-5479
A straightforward method for the synthesis of nucleotide analogues bearing a phosphorothioate moiety at the terminal position of the polyphosphate chain is described. Several nucleoside 5′-(2-thiodiphosphates) and 5′-(3-thiotriphosphates) were synthesized by treatment of the appropriate nucleotide imidazolide derivative with a ca. 4-fold excess of thiophosphate triethylammonium salt in DMF in the presence of zinc chloride. The HPLC reaction yields varied from 80% to 100%, in the majority of cases exceeding 90%. Separation was accomplished by Sephadex ion-exchange chromatography or reverse-phase HPLC with preparative yields of about 70%. 相似文献
236.
Chromatographic and spectroscopic characteristics were determined for the following stearic acid derivatives: cis- and trans-9,10-epoxystearic acids and their methyl esters, and erythro- and threo-9,10-dihydroxystearic acids and their methyl esters. It will be helpful in the further identificational investigations of the autoxidation process of oleic acid and its derivatives. 相似文献
237.
Anna Migda?-Mikuli Edward Mikuli Aneta Kowalska 《Journal of solid state chemistry》2004,177(8):2733-2739
[Ni(ND3)6](ClO4)2 has three solid phases between 100 and 300 K. The phase transitions temperatures at heating (TC1h=164.1 K and TC2h=145.1 K) are shifted, as compared to the non-deuterated compound, towards the lower temperature of ca. 8 and 5 K, respectively. The ClO4− anions perform fast, picosecond, isotropic reorientation with the activation energy of 6.6 kJ mol−1, which abruptly slow down at TC1c phase transition, during sample cooling. The ND3 ligands perform fast uniaxial reorientation around the Ni-N bond in all three detected phases, with the effective activation energy of 2.9 kJ mol−1. The reorientational motion of ND3 is only slightly distorted at the TC1 phase transition due to the dynamical orientational order-disorder process of anions. The low value of the activation energy for the ND3 reorientation suggests that this reorientation undergoes the translation-rotation coupling, which makes the barrier to the rotation of the ammonia ligands not constant but fluctuating. The phase polymorphism and the dynamics of the molecular reorientations of the title compound are similar but not quite identical with these of the [Ni(NH3)6](ClO4)2. 相似文献
238.
Teresa Kowalska 《Microchemical Journal》1977,22(2):131-134
Infrared absorption spectroscopy belongs to these analytical methods, which have wide application in estimating hydrogen-bond energies (1). In the present paper an effort was undertaken to apply the dielectric constant measurements to evaluate the mean hydrogen-bond energy levels of some selected homologous groups of chemical compounds. The chemical compounds examined in our experiment were higher fatty alcohols and acids, which showed hydrophobic properties. 相似文献
239.
The comparison of association was made for the oleyl alcohol-oleic acid systems composed in several molar ratios. The ir spectroscopy and dielectric constant measurements were applied as analytical techniques. It was stated that oleyl alcohol and oleic acid interact in a number of molar ratios giving the hydrogen-bonded associates. In the range of temparatures 30–60 °C the most stable hydrogen-bonded associate is formed in a ratio of alcohol to acid of 9:1. 相似文献
240.
Teresa Kowalska 《Monatshefte für Chemie / Chemical Monthly》1987,118(8-9):879-882
Using selected examples we demonstrate the determination of solubility of low soluble substances with the help of planar chromatography, which is a new, simple and rapid approach to the problem, to a certain extent challenging the established methods. Our approach is a practical consequence of the thermodynamic view of the chromatographic processes, involving either the adsorption or partition mechanism of separation.
Chromatographische Bestimmung der Löslichkeit von schwerlöslichen Substanzen — eine praktische Möglichkeit
Zusammenfassung An den gewählten Beispielen wird die Bestimmung der Löslichkeit schwerlöslicher Substanzen mit Hilfe der planaren Dünnschichtchromatographie demonstriert. Dieses Verfahren stellt eine neue, einfache und schnelle Methode dar, die in einem gewissen Maß in Konkurrenz zu den älteren und anerkannten Methoden tritt. Die Methode ist die praktische Konsequenz der thermodynamischen Betrachtung des chromatographischen Prozesses in der Adsorptions- und Verteilungsdünnschichtchromatographie.相似文献