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Hydroxy Derivatives (hydroxy + derivative)

Distribution by Scientific Domains

Chemistry	100%

Selected Abstracts

Hydroxy Derivatives of Diamantane, Triamantane, and [121]Tetramantane: Selective Preparation of Bis-Apical Derivatives,

EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 28 2007
Natalie A. Fokina
Abstract Functionalizations of diamantane, triamantane, and tetramantane with electrophilic reagents (Br2, nitric acid) lead to various apical and medial disubstituted products that were separated and characterized individually. The highly desirable and otherwise inaccessible thermodynamically more stable apical bis-derivatives were obtained with high preparative yields through acid catalyzed isomerizations. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source]

4- and 4,5-Substituted N -Methoxythiazole-2(3H)-thiones , Preparation,UV/Vis Spectra, and Assignment of Electronic Transitions in Comparison to N -Methoxypyridine-2(1H)-thione Using Time-Dependent Density Functional Theory Calculations

EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 5 2005
Jens Hartung
Abstract Experimentally observed absorptions in UV/Vis spectra of N -methoxy-4-methylthiazole-2(3H)-thione, N -methoxy-5-(p -methoxyphenyl)-4-methylthiazole-2(3H)-thione, N -methoxypyridine-2(1H)-thione, and selected N -hydroxy derivatives thereof have been assigned to ,,,*-type transitions as dominating character, using the results from ab initio calculations [time-dependent density functional theory (TD)RI-BLYP/TZVPP]. Theory further predicts that electronic excitations in N -methoxythiazole-2(3H)-thiones on one side and N -meth-oxypyridine-2(1H)-thione on the other side differ significantly with respect to character and statistical weight of contributing transitions. These effects originate predominantly from contributions of the endocyclic sulfur atom onto orbital energies and shapes in thiazole-2(3H)-thiones, and may be intensified by substituents such as a p -methoxyphenyl group located in position 5. Since the majority of the calculated spectral differences between thiazole- and pyridinethiones refers to excitations of low intensity, the findings from the present study correlate with two important experimental facts: (i) Apart from minor shifts in the exact spectral location of UV/Vis absorptions, electronic spectra of N -hydroxy- or N -methoxy-substituted pyridine-2(1H)-thiones and thiazole-2(3H)-thiones are surprisingly similar in shape. (ii) N -alkoxypyridine-2(1H)-thiones and N -alkoxythiazole-2(3H)-thiones liberate upon UV/Vis excitation oxygen-centered radicals with a comparable efficiency. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source]

Raman and surface-enhanced Raman spectra of flavone and several hydroxy derivatives

JOURNAL OF RAMAN SPECTROSCOPY, Issue 7 2007
Tatyana Teslova
Abstract The Raman and surface-enhanced Raman spectra (SERS) of flavone and three of its hydroxy derivatives, 3-hydroxyflavone (3-HF) and 5-hydroxyflavone (5-HF) and quercetin (3,5,7,3,,4, pentahydroxyflavone) have been obtained. The normal Raman (NR) spectra were taken in the powder form. The SERS spectra were obtained both on Ag colloids and Ag electrode substrates. Assignments of the spectrally observed normal modes were aided by density functional theory (DFT) calculations using the B3LYP functional and the 6-31 + G* basis, a split valence polarized basis set with diffuse functions. Excellent fits were obtained for the observed spectra with little or no scaling. The most intense lines of the NR spectra are those in the CO stretching region (near 1600 cm,1). These lines are often weakened by proximity to the surface, while other lines at lower wavenumbers, due to in-plane ring stretches, tend to be strongly enhanced. The SERS spectrum of flavone is weak both on the colloid and on the electrode, indicating weak attachment to the surface. In contrast, the SERS spectra of the hydroxy derivatives of flavone are intense, indicating the assistance of OH groups in attachment to the surface. The spectra of the various species are compared, and a case study of application to detection of a textile dye (Persian berries), which contains quercetin, is presented. Copyright © 2007 John Wiley & Sons, Ltd. [source]