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1.
Marilena Vasilescu Titus Constantinescu Mariana Voicescu Helge Lemmetyinen Elina Vuorimaa 《Journal of fluorescence》2003,13(4):315-322
The spectrophotometric study of luminol (LH2) in dimethyl sulfoxide (DMSO), DMSO-water solutions, and alkaline DMSO and DMSO-water solutions has been done, focusing on the effect of the KOH additon on LH2 absorption and fluorescence properties. The absorption spectra indicate an acid-base equilibrium, and the luminol dianion (L2–) formation at 3 × 10–4 – 2.4 × 10–3
M KOH. The decrease of the fluorescence intensity and the variation of the excitation spectra of LH2-DMSO-KOH solutions with KOH concentration have been similarly explained. The acid-base process is reversible. The addition of HCl to the solution with 3.0 × 10–3 M KOH leads to an increase of the fluorescence intensity to its highest value, observed in pure DMSO. The addition of HCl to the LH2-DMSO solution leads to the decrease of the fluorescence intensity as a result of the LH+
3 cation formation. In LH2-DMSO-water, the fluorescence band is shifted from 405 nm to 424 nm and increased in the intensity. In the presence of KOH (in LH2-DMSO-water-KOH solution) a new band appears, with the maximum at 485 nm and the band at 405 nm decreased. The changes in fluorescence lifetimes also evidence the different chemical species formed. 相似文献
2.
Maximiliano A. Burgos Paci Gustavo A. Argüello Plcido García Helge Willner 《国际化学动力学杂志》2003,35(1):15-19
Thermal decomposition of bis(trifluoromethyl) peroxydicarbonate has been studied. The mechanism of decomposition is a simple bond fission, homogeneous first‐order process when the reaction is carried out in the presence of inert gases such as N2 or CO. An activation energy of 28.5 kcal mol?1 was determined for the temperature range of 50–90°C. Decomposition is accelerated by nitric oxide because of a chemical attack on the peroxide forming substances different from those formed with N2 or CO. An interpretation on the influence of the substituents in different peroxides on the O? O bond is given. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 35: 15–19, 2003 相似文献
3.
The mechanism of ozone formation has been studied using 16O and 18O2. High-resolution microwave spectroscopy was used to measure the amounts of the isotopomeric ozone species formed. The study is hampered by the very rapid exchange process between the reactants, that tends to scramble the isotopes and hence give a 2:1 statistical ratio between the two possible isotopomers. We have found a strategy to come around this difficulty and conclude that the mechanism is a simple end-on-addition. 相似文献
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Torsten Küppers Martin Köckerling Prof. Dr. Helge Willner Prof. Dr. 《无机化学与普通化学杂志》2007,633(2):280-284
The new tetracyanoborate K[B(CN)4]·CH3CN was synthesized by dissolution of the solvent‐free K[B(CN)4] in acetonitrile and subsequent careful crystallization. The crystal structure has been determined by single‐crystal X‐ray diffraction. It crystallizes in the orthorhombic space group P212121 with Z = 4. Some comparisons with related structures are made, and the vibrational spectrum is discussed. 相似文献
8.
Yannick Ortin Paul O'Donohue Helge Müller-Bunz Anthony R. Manning 《Journal of organometallic chemistry》2004,689(9):1657-1664
Treatment of the aldehyde (η4-C4Ph4)Co(η5-C5H4-CHO) (4b) with tert-butyllithium or phenyllithium yields the secondary alcohols (η4-C4Ph4)Co(η5-C5H4-CH(R)OH), where R=tert-butyl (5) or phenyl (6). Protonation of 5 and 6 at −80 °C furnishes the deep purple, cobalt-stabilized cations, 7 and 8, respectively, both of which exhibit restricted rotation about the external C5H4-CHR+ linkage on the NMR time-scale. These data indicate a minimum value for the barrier to rotation of 15 kcal mol−1, but it is certainly much higher, indicating a considerable degree of C-C double bond character. X-ray crystal structures of 4b, 5 and also of the ketone (η4-C4Ph4)Co(η5-C5H4-C(O)CH3 (4a) are reported. The secondary alcohol 5 exhibits disorder in the solid state because of the presence of diastereomers as a consequence of the stereogenic center at the α-carbon and the clockwise or anticlockwise propeller orientations of the tetraphenylcyclobutadiene ligand. 相似文献
9.
[reaction: see text] A novel, mild, ecofriendly protocol for the deoxygenation of epoxides to alkenes using indium metal and indium(I) chloride or ammonium chloride in alcohol has been developed. It was necessary for the presence of good radical-stabilizing groups adjacent to the oxirane ring for the deoxygenation reaction to occur. It is proposed that this reaction occurs through an SET process with indium as an electron donor. 相似文献
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