Search results for "Spectroscopy."
showing 10 items of 9110 documents
Regioselective Synthesis of 2-Imino-1,3-thiazolidin-4-ones by Treatment ofN-(Anthracen-9-yl)-N′-ethylthiourea with Bromoacetic Acid Derivatives
2002
The reaction between N-(anthracen-9-yl)-N′-ethylthiourea (1) and methyl bromoacetate yielded mainly 2-[(anthracen-9-yl)imino]-3-ethyl-1,3-thiazolidin-4-one (2), together with some of the regioisomeric 3-(anthracen-9-yl)-2-ethylimino-1,3-thiazolidin-4-one (3). The structures of the products were elucidated by NMR techniques and, for 3, X-ray crystallographic analysis. Treatment of 1 with bromoacetyl bromide again yielded 2 and 3, but with a reversed product distribution ratio, thus providing an interesting and unexpected regioselectivity, depending on the electrophile selected. The underlying cause of the observed regioselectivity is a result of different reaction pathways taken by the two e…
13C nuclear magnetic resonance spectra of several podocarpane and cassane diterpenoids
1990
The 13C NMR spectra of several diterpenic derivatives having the podocarpane and cassane skeleton were recorded and interpreted. The most significant effects due to substituent orientation, B/C ring junction stereochemistry and conformational changes are briefly discussed.
Antidiabetische wirkstoffe. V Lang- und verzweigtkettig substituierte chlor-dihexylamino-1,3,5-triazine
1985
Die nucleophile Substitution eines Chloratoms in 2,4-Dichlor-6-dihexylamino-1,3,5-triazin (1) durch Amine (2a-c) fuhrt zu den Alkylamino-chlor-dihexylamino-1,3,5-triazinen 3a-c. Fur Strukturtyp 3 typische Signale in den 1H-NMR-Spektren sind das Triplett bei 0,9 ppm fur die endstandigen Methylgruppen und das Multiplett bei 3,3-3,65 ppm fur die den Stickstoffatomen benachbarten Methylengruppen. In Verbindungsklasse 3 finden sich Vertreter mit antidiabetischer, trichomonazider, antiviraler und anthelminthischer Wirksamkeit. The nucleophilic substitution of one chlorine atom in 2,4-dichloro-6-dihexylamino-1,3,5-triazine (1) by amines 2a-c leads to the alkylamino-chlorodihexylamino-1,3,5-triazin…
ChemInform Abstract: COMPLEXES OF ORGANOMETALLIC COMPOUNDS PART 42, SPECTROSCOPIC STUDIES OF N,N′-ETHYLENEBIS(ACETYLACETONEIMINE) AND N,N′-ETHYLENEBI…
1975
Abstract The nature of the 1 1 adducts formed from the ligands N,N′-ethylenebis(acetylacetonemine) and N,N′-ethylenebis(salicylideneimine) with Ph2PbCl2 and PhTlCl2 was investigated in the solid state and in methanol solution by IR, electronic and PMR spectroscopy, and by osmometry and conductivity. The adducts exist only in the solid state and dissociate fully into the parent compounds in solution. Polymeric structures are proposed for the solids, in which bis-monodentate ligands bridge the organometallic moieties.
On the Occurrence of Flavonoids in the acrocarpous Mosses
1978
Summary By means of paper chromatography two flavonoids were isolated from the methanolic extract of the moss Mnium undulatum. One substance was identified by chromatographic data, absorption spectra and acid hydrolysis as isovitexin-7-0-glucoside (saponarin). The second substance resists acid hydrolysis and is by chromatography and absorption spectrum identical with apigenin-6,8-di-C-glycoside (viccnin).
Some observations on the determination of the methyl parathion-parathion ratio in binary mixtures by infrared spectroscopy
1989
Abstract The determination of the methyl parathion/parathion ratio in binary mixtures has been carried out by infrared spectroscopy using a simple and easy model for the treatment of the spectra obtained from sample thin films using sodium chloride windows. The model is based on the use of two bands, one at 974 cm−1, characteristic of parathion, and other at 1348 cm−1, common to both compounds. From the spectra of pure parathion samples and mixtures of known composition of methyl parathion and parathion, two constants have been obtained. These constants relate the absorption of each compound at 1348 cm−1 to the absorption of parathion at 974 cm−1. Eighteen synthetic samples have been analyz…
1988
Hydrolysis of Phytic Acid by Microwave Treatment: Application to Phytic Acid Analysis in Pharmaceutical Preparations
1998
Abstract The acid hydrolysis of phytic acid in a Teflon reactor using a domestic microwave oven has been studied and compared with other reported procedures. In 0.44 M HCl quantitative hydrolysis was achieved with six heating stages of 2 min each. A lower yield was obtained with H 2 SO 4 and HNO 3 . The analytical use of this hydrolysis to determine phytic acid by indirect determination of phosphate has been demonstrated by analysis of three pharmaceutical formulations. No sample pretreatment other than obtaining a homogeneous suspension was necessary.
New Sesquiterpene Lactones and Other Constituents fromCentaurea paui
1997
Aerial parts of Centaurea paui afforded, in addition to several known sesquiterpene lactones, the two new elemanolides 2–4, the new elemane derivative 5 as well as the five new heliangolides 14–18. Their structures were elucidated by spectroscopic methods, especially high-field NMR spectroscopy. The structure of the heliangolide 12 previously isolated from this plant, has been confirmed by X-ray diffraction.