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Hydroxy Groups (hydroxy + groups)
Selected AbstractsFluorous Glycopeptide Synthesis Without Protection of Sugar Hydroxy Groups.CHEMINFORM, Issue 31 2005Mamoru Mizuno No abstract is available for this article. [source] Unusual Regioselective Acylation of the Primary Hydroxy Groups of ,-Cyclodextrin.CHEMINFORM, Issue 24 2003A. E. Glazyrin No abstract is available for this article. [source] ChemInform Abstract: An Efficient Method for the p-Methoxybenzylation of Hydroxy Groups with 2-(4-Methoxybenzyloxy)-3-nitropyridine.CHEMINFORM, Issue 42 2001Masakazu Nakano Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] ChemInform Abstract: Nonenzymatic Kinetic Resolution of Secondary Alcohols: Enantioselective SN2 Displacement of Hydroxy Groups by Halogens in the Presence of Chiral BINAP.CHEMINFORM, Issue 30 2001Govindasamy Sekar Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Two New Iron(II) Spin-Crossover Complexes with N4O2 Coordination Sphere and Spin Transition around Room TemperatureEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 36 2009Birgit Weber Abstract The reaction of iron(II) acetate with the tetradentate Schiff base like ligand H2L1 {[3,3,]-[4,5-dihydroxy-1,2-phenylenebis(iminomethylidyne)bis(2,4-pentanedion)]} leads to the formation of the complex [FeL1(MeOH)]. Reaction of this complex with pyridine (py) or N,N,-dimethylaminopyridine (dmap) leads to the two N4O2 -coordinated complexes [FeL1(py)2]·py (1) and [FeL1(dmap)2]·MeOH·0.5dmap (2). Both complexes are spin-crossover compounds that were characterised by using magnetic measurements, X-ray crystallography and temperature-dependent 1H NMR spectroscopy. Special attention was given to the role of the two hydroxy groups on the phenyl ring in the formation of a hydrogen-bonding network and the influence of this network on the spin-transition properties. Although only a gradual spin crossover was observed for both complexes, the transition temperature was shifted to higher temperatures relative to that of the complexes with no additional hydroxy groups at the Schiff base like ligand. The hydrogen-bonding network was responsible for this effect.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Base-Induced Formation of Two Magnesium Metal-Organic Framework Compounds with a Bifunctional Tetratopic LigandEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 23 2008Pascal D. C. Dietzel Abstract Two coordination polymers constructed from magnesium and the tetratopic organic linker 2,5-dihydroxyterephthalic acid are reported, denominated CPO-26-Mg and CPO-27-Mg. The organic component carries two different types of protic functional groups. The degree of deprotonation of the organic component can be regulated by the amount of sodium hydroxide employed in the synthesis, thus determining which of the compounds forms. In CPO-26-Mg, only the carboxylic acid groups of the linker are deprotonated and take part in the construction of the three-dimensional framework. The structure is non-porous, and its topology is based on the PtS net. In CPO-27-Mg, both the carboxylic acid and the hydroxy groups are deprotonated and involved in the construction of a microporous three-dimensional framework which is based on a honeycomb motif containing large solvent-filled channels. The metal atoms are arranged in chiral chains along the intersection of the honeycomb and contain one water molecule in their coordination sphere, which allows for the creation of coordinatively unsaturated metal sites upon dehydration. CPO-27-Mg is a potentially useful lightweight adsorbent with a pore volume of 60,% of the total volume of the structure and an apparent Langmuir surface area of up to 1030 m2,g,1. Its thermal stability was investigated by thermogravimetry and variable-temperature powder X-ray diffraction, which shows framework degradation to commence at 160 °C in air, at 235 °C under nitrogen, and at 430 °C in a dynamic vacuum. Thermogravimetric dehydration and re-hydration experiments at miscellaneous temperatures indicate that it is possible to obtain open metal sites in CPO-27-Mg, but the water is more tightly bound in this material than in the previously reported isostructural nickel compound.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Diastereopure Cationic NCN-Pincer Palladium Complexes with Square Planar ,4 - N,C,N,O CoordinationEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 22 2006Silvia Gosiewska Abstract Neutral NCN-pincer palladium bromide complex 2 containing the monoanionic, enantiopure pincer ligand 2,6-bis{[(S)-2-hydroxymethyl-1-pyrrolidinyl]methyl}phenyl bromide (1) with bis- ortho -(S)-prolinol substituents was synthesized and isolated as a mixture of three stereoisomers [(SN,SN,SC,SC), (RN,SN,SC,SC), and (RN,RN,SC,SC)] in a 1:1:1 ratio. Upon abstraction of the bromide ion from the unresolved mixture of 2, single diastereoisomers of the cationic complexes [3]BF4 and [3]PF6, respectively, were formed with a unique,4 - N,C,N,O coordination mode of ligand 1. X-ray crystal structure determination established the intramolecular,4 - N,C,N,O coordination of 1 to palladium where the typical mer -,3 - N,C,N pincer coordination is accompanied by coordination of one of the hydroxy groups of the (S)-prolinol moieties. The water molecule that was cocrystallized in the crystal structure of [3]PF6 does not coordinate to palladium, but instead is involved in a hydrogen bonding network. The catalytic potential of both cationic complexes, [3]BF4 and [3]PF6, was tested in an aldol reaction of aldehydes with methyl isocyanoacetate to yield the oxazoline products as racemic mixtures.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] First (Peroxo)vanadium(V) Complex with Heteroligand Formed in Reaction System , Synthesis, Structure and Reactivity of K[VO(O2)(omeida)]·H2O {omeida = N -[2-(2-oxomorpholine-4-yl)ethyl]iminodiacetato(2,)}EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 11 2003Michal Sivák Abstract The crystalline peroxo complex of vanadium(V), K[VO(O2)(omeida)]·H2O, where omeida is a ,-lactone derivative, N -[2-(2-oxomorpholine-4-yl)ethyl]iminodiacetate(2,), has been obtained by reaction of vanadate with H2O2 and N -(2-hydroxyethyl)ethylenediaminetriacetic acid (HEDTA) in acidic aqueous solution at pH = 3 and 278 K. X-ray analysis revealed a distorted pentagonal-bipyramidal coordination around the vanadium atom, with a typical cis arrangement of oxo and peroxo ligands in apical and equatorial positions, respectively. Two amino nitrogen atoms of the tetradentate omeida(2,)-N1,N2,O1,O2 ligand occupy the neighbouring equatorial positions of the pentagonal plane, and two oxygen atoms of carboxymethyl groups bound to the same N1 nitrogen atom are in equatorial and apical positions. The six-membered lactone ring in omeida was formed in the reaction solution from carboxy and hydroxy groups not involved in coordination with the vanadium atom. The 51V NMR spectra of K[VO(O2)(omeida)]·H2O, and of peroxovanadate/HEDTA/H2O and vanadate/HEDTA/H2O solutions, as well as the 1H NMR spectrum of HEDTA, proved that lactone ring closure proceeds only in peroxovanadate but not vanadate solutions. Spectroscopic investigation of the oxygen transfer reaction from the peroxo ligand in [VO(O2)(omeida)], to the thiolato sulfur atom in [Co(en)2{S(CH2)2NH2}]2+ or [Co(en)2(cyst)]+, and of the oxidation of N -acetyl- L -cysteine by K[VO(O2)(omeida)]·H2O, revealed much more complicated reaction mechanisms than those of other (amino-polycarboxylato)monoperoxo complexes of vanadium(V). (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source] N -methyl-1-(1,3-benzodioxol-5-yl)-2-butanamine (MBDB): its properties and possible risksADDICTION BIOLOGY, Issue 3 2000L. A. G. J. M. Van Aerts MBDB (N -methyl-1-(1,3-benzodioxol-5-yl)-2-aminobutane) is the ,-ethyl homologue of MDMA (3,4-methylenedioxy-N-methylamphetamine). MBDB is metabolized and excreted similarly to MDMA: presumably, the majority of oral MBDB is excreted in urine unmetabolized. The main metabolic routes in man are thought to be O-dealkylation and subsequent methylation, sulphation and glucuronidation of the newly formed hydroxy groups. The major acute neuropharmacological effects of MBDB in the rat are an increase in serotonin release in the brain and an inhibition of serotonin and noradrenaline re-uptake. These effects compare well with those of MDMA, although the latter is more potent. MBDB may also slightly increase dopamine release and inhibit dopamine re-uptake, but to a lesser extent than MDMA. This is important, as dopamine release has been implicated in the reinforcing qualities of substances such as cocaine and amphetamine. The neuroendocrine effects of MBDB resemble those of MDMA. Both substances increase plasma ACTH, corticosterone, prolactin and renin. The neurophysiological effects of MBDB are characterized by a decrease in electrical activity throughout the brain, most notably in the alpha 2 and delta frequency bands. In contrast, hallucinogens increase the activity in the alpha 1 band, especially in the corpus striatum. In drug discrimination tests in the rat, MBDB, like MDMA, can be distinguished clearly from both stimulants and hallucinogens. The class of substances to which MBDB belongs may be named entactogens. MBDB dose-dependently increases locomotor activity and decreases exploratory behaviour in the rat and causes distress vocalization and wing extension in the newly hatched chicken. The rewarding properties of MBDB appear to be smaller than those of MDMA, as suggested by a 2.5 times weaker potency in the conditioned place preference test in rats. The main subjective effects of MBDB in man are a pleasant state of introspection, with greatly facilitated interpersonal communication and a pronounced sense of empathy and compassion between subjects. In this respect, MBDB again resembles MDMA. However, there are also differences. MBDB has a slower and more gentle onset of action than MDMA, produces less euphoria and has less stimulant properties. The few toxicological data available suggest that MBDB may cause serotonergic deficits in the brain, although the potency of MBDB to cause this neurotoxic effect is smaller than that of MDMA. Severe acute reactions in man as have been reported for MDMA have not been published for MBDB. The dependence potential of MBDB appears to be small, probably even smaller than that of MDMA. MBDB has been available at least since 1994 but its position on the synthetic drugs market is marginal. Subjective reports indicate that MBDB is less popular among users than MDMA. The reason may be that MBDB produces less euphoria than MDMA. Another possible explanation is that MBDB largely lacks the stimulant properties of MDMA. We calculated a margin of safety with a method similar to one used in the risk assessment of pharmaceuticals. The results suggest that MBDB is three times less likely to cause serotonergic brain deficits than MDMA. However, it should be noted that for both substances the margin of safety is less than one, indicating that the risk of neurotoxicity is not negligible. In animals, serotonergic brain deficits after exposure to MDMA have been linked to the degeneration of serotonergic nerve terminals. [source] Towards Selective Recognition of Sialic Acid Through Simultaneous Binding to Its cis -Diol and Carboxylate FunctionsEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 17 2010Martín Regueiro-Figueroa Abstract A series of receptors containing phenylboronic acid and urea or thiourea units have been designed for simultaneous recognition of the cis -diol and carboxylate functions of sialic acids, which are known to be overexpressed on the surfaces of tumor cells. The interaction of the receptors with 5-acetylneuraminic acid (Neu5Ac) and 2-,- O -methyl Neu5Ac (MeNeu5Ac) in DMSO solution has been investigated bymeans of spectrophotometric titrations and 1H, 13C, and 11B NMR spectroscopy. Additionally, we have also investigated the binding of these receptors with competing monosaccharides such as D -(+)-glucose, D -fructose, methyl ,- D -galactoside, and methyl ,- D -mannoside. Our results show that 2-{[3-(4-nitrophenyl)thioureido]methyl}phenylboronic acid (3a) recognizes both Neu5Ac and MeNeu5Ac with good selectivity with regard to the remaining monosaccharides investigated. DFT calculations performed at the B3LYP/6-31G(d) level show that this selectivity is due to a cooperative two-site binding of Neu5Ac through 1) ester formation by interaction at the phenylboronic acid function of the receptor and 2) hydrogen-bond interaction between the thiourea moiety and the carboxylate group of Neu5Ac. Compound 3a can therefore be considered a promising synthon for the design of contrast agents for magnetic resonance imaging of tumors. In contrast, the analogue of 3a containing a urea moiety , compound 3b , displays strong binding to all monosaccharides investigated, due to two-site binding through interaction on the phenylboronic acid function of the receptor and a hydrogen-bond interaction between the urea moiety and the sugar hydroxy groups. [source] Silylene/Oxazolidinone Double-Locked Sialic Acid Building Blocks for Efficient Sialylation Reactions in DichloromethaneEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 25 2009Shinya Hanashima Abstract We describe efficient sialylation reactions in CH2Cl2 with the use of silylene/oxazolidinone double-locked sialic acid building blocks. The building blocks were synthesized from 4,5-oxazolidinone-protected phenylthiosialoside. In sialylation reactions towards primary and relatively reactive secondary hydroxy groups on the galactosides, the double-locked building blocks provided desired coupling products in good yields with excellent ,-selectivities. In the sialylation reaction with the C3-OH of the galactoside, the double-locked building blocks expressed significantly better ,-selectivity in comparison with the results obtained by using the oxazolidinone-locked building block. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Crystal Structures of Conformationally Locked Cyclitols: An Analysis of Hydrogen-Bonded Architectures and their Implications in Crystal EngineeringEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 3 2007Goverdhan Mehta Abstract A qualitative study has been carried out on selected polycyclitols to evaluate the potential of conformational locking of hydroxy groups in lending predictability to the O,H···O hydrogen-bonding network observed in the crystal structures of such compounds. The polycyclitols employed in this study are conformationally locked with all the hydroxy groups destined to be axial owing to the trans ring fusion(s) in the polycyclic carbon framework. The consequent formation of intramolecular O,H···O hydrogen bonds between the 1,3- syn diaxial hydroxy groups now permits any packing pattern in the polycyclitols to be described in terms of a small group of intramolecularly bonded molecular motifs linked to their respective neighbors by four O,H···O bonds. By using this model and the results of CSD analyses of polyols as a guide, the O,H···O hydrogen-bonded packing motifs most likely to be observed in the crystal structure of each polycyclitol were proposed and compared with those obtained experimentally. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Macrocyclic Cyclo[n]malonates , Synthetic Aspects and Observation of Columnar Arrangements by X-ray CrystallographyEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 10 2006Nikos Chronakis Abstract A variety of achiral and chiral macrocyclic oligomalonates were synthesised in a one-step procedure through condensation of malonyl dichloride with ,,,-diols. We have investigated the applicability of this method by varying the length and type of the spacers in the diol. Product distribution analysis revealed that the preferential formation of monomeric, dimeric, or trimeric macrocyclic malonates can be controlled by choosing diols with specific spacers connecting the hydroxy groups. Of special interest are the macrocyclic bismalonates, as they show pronounced crystallisability and arrange into columnar motifs in the solid state. They feature distinctive dihedral angles: all ester moieties adopt anti conformations whereas the planes of the carboxy moieties of each malonate residue arrange in an approximately orthogonal fashion. The latter geometry is enforced by the macrocyclic structures, as revealed by a conformational search in the Cambridge Structural Database. The X-ray diffraction data show that C=O···H,C, and C,O···H,C hydrogen bonds stabilise the columnar arrangement of the dimeric rings with formation of tubular assemblies. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] New Functionalised Hydroxymethyl Ketones from the Mild and Chemoselective KMnO4 Oxidation of Chiral Terminal OlefinsEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 1 2006Carlo Bonini Abstract Various terminal olefinic compounds are directly converted into the corresponding ,-hydroxy ketones in good yields by potassium permanganate oxidation. The reaction is also highly chemoselective in the presence of differently protected hydroxy groups and can be utilised for the preparation of polyfunctional compounds such as polyols. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Solution Synthesis of Two Orthogonally Protected Lactosides as Tetravalent Disaccharide-Based ScaffoldsEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 13 2004Sergio Castoldi Abstract Two tetravalent lactosidic scaffolds have been synthesised in solution from commercial lactose. Careful manipulation of the protecting groups allowed us to orthogonally protect four OH groups for their use as diversity sites for the development of broad screening libraries of sugar mimics. The selective access to each of these hydroxy groups has been demonstrated on scaffold 2 by deprotection and functionalisation with p -fluorophenyl isocyanate. Finally, the 6-OH derivative of compound 2 was covalently attached to a polymeric support. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] Palladium-Catalyzed Aryl Amination Reactions of 6-Bromo- and 6-Chloropurine NucleosidesADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 10 2010Abstract Palladium-catalyzed CN bond forming reactions of 6-bromo- as well as 6-chloropurine ribonucleosides and the 2,-deoxy analogues with arylamines are described. Efficient conversions were observed with palladium(II) acetate/Xantphos/cesium carbonate, in toluene at 100,°C. Reactions of the bromonucleoside derivatives could be conducted at a lowered catalytic loading [5,mol% Pd(OAc)2/7.5,mol% Xantphos], whereas good product yields were obtained with a higher catalyst load [10,mol% Pd(OAc)2/15,mol% Xantphos] when the chloro analogue was employed. Among the examples evaluated, silyl protection for the hydroxy groups appears better as compared to acetyl. The methodology has been evaluated via reactions with a variety of arylamines and by synthesis of biologically relevant deoxyadenosine and adenosine dimers. This is the first detailed analysis of aryl amination reactions of 6-chloropurine nucleosides, and comparison of the two halogenated nucleoside substrates. [source] A theoretical investigation on the structures, densities, detonation properties, and pyrolysis mechanism of the nitro derivatives of phenolsINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 9 2010Guixiang Wang Abstract The nitro derivatives of phenols are optimized to obtain their molecular geometries and electronic structures at the DFT-B3LYP/6-31G* level. Detonation properties are evaluated using the modified Kamlet,Jacobs equations based on the calculated densities and heats of formation. It is found that there are good linear relationships between density, detonation velocity, detonation pressure, and the number of nitro and hydroxy groups. Thermal stability and pyrolysis mechanism of the title compounds are investigated by calculating the bond dissociation energies (BDEs) at the unrestricted B3LYP/6-31G* level. The activation energies of H-transfer reaction is smaller than the BDEs of all bonds and this illustrates that the pyrolysis of the title compounds may be started from breaking OH bond followed by the isomerization reaction of H transfer. Moreover, the CNO2 bond with the smaller bond overlap population and the smaller BDE will also overlap may be before homolysis. According to the quantitative standard of energetics and stability as a high-energy density compound, pentanitrophenol essentially satisfies this requirement. In addition, we have discussed the effect of the nitro and hydroxy groups on the static electronic structural parameters and the kinetic parameter. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010 [source] Exploring the Biocatalytic Scope of Alditol Oxidase from Streptomyces coelicolorADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 10 2009W. van Hellemond Abstract The substrate scope of the flavoprotein alditol oxidase (AldO) from Streptomyces coelicolor A3(2), recombinantly produced in Escherichia coli, was explored. While it has been established that AldO efficiently oxidizes alditols to D -aldoses, this study revealed that the enzyme is also active with a broad range of aliphatic and aromatic alcohols. Alcohols containing hydroxy groups at the C-1 and C-2 positions like 1,2,4-butanetriol (Km=170,mM, kcat=4.4,s,1), 1,2-pentanediol (Km=52,mM, kcat=0.85,s,1) and 1,2-hexanediol (Km=97,mM, kcat=2.0,s,1) were readily accepted by AldO. Furthermore, the enzyme was highly enantioselective for the oxidation of 1,2-diols [e.g., for 1-phenyl-1,2-ethanediol the (R)-enantiomer was preferred with an E -value of 74]. For several diols the oxidation products were determined by GC-MS and NMR. Interestingly, for all tested 1,2-diols the products were found to be the ,-hydroxy acids instead of the expected ,-hydroxy aldehydes. Incubation of (R)-1-phenyl-1,2-ethanediol with 18O-labelled water (H218O) revealed that a second enzymatic oxidation step occurs via the hydrate product intermediate. The relaxed substrate specificity, excellent enantioselectivity, and independence of coenzymes make AldO an attractive enzyme for the preparation of optically pure 1,2-diols and ,-hydroxy acids. [source] Development of a Supported Ionic Liquid Phase (SILP) Catalyst for Slurry-Phase Friedel,Crafts Alkylations of CumeneADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 3 2009J. Joni Abstract A supported ionic liquid phase (SILP) catalyst material has been developed based on a silica support coated with an acidic chloroaluminate ionic liquid. Compared to the results in a liquid-liquid biphasic reaction these materials showed in the isopropylation of cumene a clearly different selectivity which was found to be related to a reduction of the ionic liquid's acidity by the untreated silica support. By pretreating the support with a defined amount of ionic liquid for neutralization and removal of surface hydroxy groups, a well defined, very active and also very selective SILP catalyst for slurry phase Friedel,Crafts alkylation was obtained. [source] A Convenient and Effective Method for the Regioselective Deuteration of AlcoholsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 14-15 2008Tomohiro Maegawa Abstract The convenient and regioselective deuteration of hydroxy groups on vicinal carbons was achieved by the combination of 5% ruthenium on carbon (Ru/C), hydrogen gas and deuterium oxide (D2O). [source] The crystal structure of perdeuterated methanol hemiammoniate (CD3OD·0.5ND3) determined from neutron powder diffraction data at 4.2 and 180,KJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 2 2010A. D. Fortes The crystal structure of perdeuterated methanol hemiammoniate, CD3OD·0.5ND3, has been solved from neutron powder diffraction data collected at 4.2 and 180,K. The structure is orthorhombic, space group Pn21a (Z = 4), with unit-cell dimensions a = 12.70615,(16), b = 8.84589,(9), c = 4.73876,(4),Å, V = 532.623,(8),Å3 [,calc = 1149.57,(2),kg,m,3] at 4.2,K, and a = 12.90413,(16), b = 8.96975,(8), c = 4.79198,(4),Å, V = 554.656,(7),Å3 [,calc = 1103.90,(1),kg,m,3] at 180,K. The crystal structure was determined by ab initio methods from the powder data; atomic coordinates and isotropic displacement parameters were subsequently refined by the Rietveld method to Rp, 2% at both temperatures. The crystal structure comprises a three-dimensionally hydrogen-bonded network in which the ND3 molecules are tetrahedrally coordinated by the hydroxy moieties of the methanol molecule. This connectivity leads to the formation of zigzag chains of ammonia,hydroxy groups extending along the c axis, formed via N,D···O hydrogen bonds; these chains are cross-linked along the a axis through the hydroxy moiety of the second methanol molecule via N,D···O and O,D···O hydrogen bonds. This `bridging' hydroxy group in turn donates an O,D···N hydrogen bond to ammonia in adjacent chains stacked along the b axis. The methyl deuterons in methanol hemiammoniate, unlike those in methanol monoammoniate, do not participate in hydrogen bonding and reveal evidence of orientational disorder at 180,K. The relative volume change on warming from 4.2 to 180,K, ,V/V, is + 4.14%, which is comparable to, but more nearly isotropic (as determined from the relative change in axial lengths, e.g.,a/a) than, that observed in deuterated methanol monohydrate, and very similar to what is observed in methanol monoammoniate. [source] Shade darkening effect of polyorganosiloxane modified with amino and hydroxy groups on dyed polyester microfiber fabricJOURNAL OF APPLIED POLYMER SCIENCE, Issue 2 2007Kongliang Xie Abstract The novel polyorganosiloxane material S-101 modified with amino and hydroxy groups is synthesized. Shade darkening effect of modified polyorganosiloxane on dyed polyester microfiber fabric is investigated by reflectance spectrum, color yield (K/S), and the color differences (,E). The colorimetric data of CIELAB is discussed. The results show that the novel material of silicone polymer modified with amino and hydroxy groups has excellent shade darkening effect on dyed polyester microfiber fabric. The rates of the color yield increase (I%) of all dyed fabric with four dyes (Disperse Yellow S-4RL, Red GS, Blue 2BLN, and Black SF-R) exceed 10%. The shapes of the reflectance spectra curves of the dyed fabrics before and after treated with S-101 are not noticeable change. The dyed fabrics with the polymer have not significant effect on the wash fastness and wet rubbing fastness. The low reflectance thin film on dyed fabrics is formed. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007 [source] Designer drug 2,4,5-trimethoxyamphetamine (TMA-2): Studies on its metabolism and toxicological detection in rat urine using gas chromatographic/mass spectrometric techniquesJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 9 2006Andreas H. Ewald Abstract Studies are described on the metabolism and the toxicological detection of the amphetamine-derived designer drug 2,4,5-trimethoxyamphetamine (TMA-2) in rat urine using gas chromatographic/mass spectrometric (GC/MS) techniques. The identified metabolites indicated that TMA-2 was metabolized by oxidative deamination to the corresponding ketone followed by reduction to the corresponding alcohol, O -demethylation followed by oxidative deamination, and finally O,O -bis-demethylation. All metabolites carrying hydroxy groups were found to be partly excreted in urine as glucuronides and/or sulfates. The authors' systematic toxicological analysis (STA) procedure using full-scan GC/MS after acid hydrolysis, liquid-liquid extraction, and microwave-assisted acetylation allowed the detection, in rat urine, of an intake of TMA-2 that corresponds to a common drug users' dose. Assuming similar metabolism, the described STA procedure in human urine should be suitable as proof of an intake of TMA-2. Copyright © 2006 John Wiley & Sons, Ltd. [source] Mass spectrometry of steroid glucuronide conjugates.JOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 9 2001-diol 3-, -steroid-, -steroid-17- O -, 17-glucuronides, 3-keto-, Electron impact fragmentation of 3-keto-4-en-, glucuronides Abstract The steroid glucuronide conjugates of 16,16,17-d3 -testosterone, epitestosterone, nandrolone (19-nortestosterone), 16,16,17-d3 -nortestosterone, methyltestosterone, metenolone, mesterolone, 5,-androstane-3,,17,-diol, 2,2,3,4,4-d5 -5,-androstane-3,,17,-diol, 19-nor-5,-androstane-3,,17,-diol, 2,2,4,4-d4 -19-nor-5,-androstane-3,,17,-diol and 1,-methyl-5,-androstane-3,/,,17,-diol were synthesized by means of the Koenigs,Knorr reaction. Selective 3- or 17- O -conjugation of bis-hydroxylated steroids was performed either by glucuronidation of the corresponding steroid ketole and subsequent reduction of the keto group or via a four-step synthesis starting from a mono-hydroxylated steroid including (a) protection of the hydroxy group, (b) reduction of the keto group, (c) conjugation reaction and (d) removal of protecting groups. The mass spectra and fragmentation patterns of all glucuronide conjugates were compared with those of the commercially available testosterone glucuronide and their characterization was performed by gas chromatography/mass spectrometry and nuclear magnetic resonance spectroscopy. For mass spectrometry the substances were derivatized to methyl esters followed by trimethylsilylation of hydroxy groups and to pertrimethylsilylated products using labelled and unlabelled trimethylsilylating agents. The resulting electron ionization mass spectra obtained by GC/MS quadrupole and ion trap instruments, full scan and selected reaction monitoring experiments are discussed, common and individual fragment ions are described and their origins are proposed. Copyright © 2001 John Wiley & Sons, Ltd. [source] The role of specific interactions in crystalline complex formation.JOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 5 200210-bis(4-bromophenyl)-, 10-dihydroanthracene with dimethyl sulfoxide, 10-dihydroxy-, Structural, thermochemical analysis of inclusion compounds of cis -, trans - Abstract Referring to a crucial problem in crystal engineering and co-crystallization of host,guest complexes, whether the non-covalent supramolecular interactions existing in a pre-crystalline solution state may determine the subsequent crystal structure, the particular inclusion properties of host compounds 1, cis - and 2, trans -9,10-bis(4-bromophenyl)-9,10-dihydroxy-9,10-dihydroanthracene, with dimethyl sulfoxide (DMSO) were studied by using x-ray structure analysis and calorimetric methods. Both hosts form crystalline inclusion complexes with DMSO showing 2:3 (1·DMSO) and 1:4 (2·DMSO) host:guest composition. The crystal structure of 1·DMSO (2:3) is dominated by a strong bifurcated acceptor-type H bond interaction involving 1 and one of the DMSO molecules. Titration calorimetric investigations in solution also confirm the formation of a stable 1·DMSO (1:1) complex unit, suggesting that for crystal nuclei of 1·DMSO (2:3) the pre-formed 1:1 host,guest complex is the relevant building block while the additional molecules of DMSO fill lattice voids. In contrast, compound 2 with a trans configuration of the two hydroxy groups gives much weaker complexation with DMSO in solution, which is in agreement with single H-bond interaction, also realized in the crystal structure of the respective inclusion complex. Thermal decomposition (TG,DSC) measurements of the crystalline complexes supply supporting data for these findings. Copyright © 2002 John Wiley & Sons, Ltd. [source] Poly(lactic acid) brushes grow longer at lower temperaturesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 15 2010Lebo Xu Abstract Poly(lactic acid) (PLA) brushes prepared by the ring opening of lactide were thicker when polymerized at a lower temperature (25 °C) than was typically used for polymerization in solution. The molecular weight of solution polymerized lactide was also higher when lactide was polymerized at 25 °C compared with polymerization at higher temperatures. However, the yield of PLA was low at this temperature. These results highlight the different requirements for solution polymerization and brush growth. In the former case, both percentage of conversion and molecular weight are important considerations. In the latter case, however, percentage of conversion is unimportant as a brush represents a very small amount of polymer. It was also shown during the course of these studies that the native hydroxy groups on silicon substrates and silanols in solution were equally good initiators when compared with hydroxy terminated self-assembled monolayers on gold and alcohols, respectively. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3362,3367, 2010 [source] Catalytic reactions of oxetanes with protonic reagents and aprotic reagents leading to novel polymersJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 5 2007Hiroto Kudo Abstract This paper reports new addition reactions of oxetanes with certain protonic reagents such as carboxylic acid, phenol, and thiol, and with certain aprotic reagents such as acyl chloride, thioester, phosphonyl dichloride, silyl chloride, and chloroformate using quaternary onium salts as catalysts. The kinetic study of the addition reactions of oxetanes was also investigated. These new addition reactions were applicable to the synthesis of new polymers. These polyaddition systems could also construct both polymer main chains and reactive side chains. The alternating copolymerization of oxetanes with carboxylic anhydride was performed. Furthermore, it was found that anionic ring-opening polymerization of oxetanes containing hydroxy groups proceeded to afford the hyperbranched polymer (HBP) with an oxetanyl group and many hydroxy groups at the ends of the polymer chains. Alkali developable photofunctional HBPs were synthesized by the polyaddition of bis(oxetane)s or tris(oxetane)s, and their patterning properties were examined, too. The photo-induced cationic polymerization of the polymers with pendant oxetanyl groups and the thermal curing reactions of polyfunctional oxetanes (oxetane resins) were also examined to give the crosslinking materials quantitatively. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 709,726, 2007 [source] Multisensitive polymers based on 2-vinylpyridine and N -isopropylacrylamide ,JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 21 2001Sebastian Wohlrab Abstract Poly(2-vinylpyridine) (P2VP) containing functionalized end groups was synthesized using nitroxyl-mediated radical polymerization with a hydroxy-functionalized stable free radical. It was shown that P2VP could be synthesized with variable molar masses and low polydispersities. The transformation of the hydroxy groups to an acrylic ester led to the formation of macromonomers. A free-radical copolymerization of these macromonomers with N -isopropylacrylamide gave a graft copolymer with a poly(N -ispopropylacrylamide) backbone and P2VP side chains. Polymers containing different amounts of the monomers were synthesized. It was possible to vary both the amount of P2VP side chains at a constant chain length of the macromonomer and the chain length at a nearly constant chain number. The behavior of the multifunctional macromolecules at different temperatures and pH values was investigated using dynamic light scattering and DSC. The macromolecules were found to retain the specific properties of the homopolymers. The hydrodynamic radii of the synthesized graft copolymers were both dependent on the temperature and pH value. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3797,3804, 2001 [source] Synthesis, characterization, and thermal properties of ladderlike polyepoxysiloxanesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 13 2001Yuhui Lin Abstract Starting from trichlorosilanes and using 1,4-phenylenediamine as a template, we have synthesized some ladderlike poly(glycidyl- co -alkyl/aryl)siloxanes (polyepoxysiloxanes or polyepoxies for short). The structures of copolymers were confirmed through IR, 1H NMR, elemental analyses, and gel permeation chromatography. Curing behaviors of these polyepoxies in the absence and presence of a curing agent have been studied with DSC. It was shown that these epoxies could be cured without any curing agent. Copolymers having aromatic groups showed higher curing reactivity than those having alkyl groups. The experimental results also demonstrate that the curing reaction occurred solely via epoxy functionality, not via the condensation reaction of the hydroxy groups located at the end of polymer main chains. The thermal stability of the cured polymers was examined by thermogravimetric analysis. The results confirm that polyepoxies with aromatic groups had better thermal stability than those with alkyl groups. It was also found that polyepoxies cured with a diamine have a higher thermal stability than those cured in the absence of a curing agent. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2215,2222, 2001 [source] Effects of Saccharide Set Retarders on the Hydration of Ordinary Portland Cement and Pure Tricalcium SilicateJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 1 2010Linghong Zhang The effects of aliphatic sugar alcohols (e.g., threitol, xylitol, sorbitol) on the hydration of tricalcium silicate (C3S) and ordinary portland cement (OPC) were investigated and compared with those of sucrose, a well-established cement set retarder. Only sugar alcohols which contain threo diol functionality retarded the setting of C3S and OPC, their efficacy increasing with the number of threo hydroxy pairs and, to a smaller extent, with the overall population of hydroxy groups. None, however, were as effective as sucrose. The initial and final setting times increased exponentially with the concentration of saccharide, although the hydration of OPC was less inhibited than that of C3S. Saccharides function as "delayed accelerators," that is, cement hydration is first inhibited and then proceeds faster than in saccharide-free cement. This behavior is consistent with the theory that the induction period is controlled by slow formation and/or poisoning of the stable calcium silicate hydrate (CSH) nuclei. The early inhibiting influence of saccharides on CSH precipitation is apparently stronger than on the growth of crystalline calcium hydroxide. Saccharides did not negatively affect the degree of hydration and compressive strength of fully set OPC paste; on the contrary, sorbitol yielded modest increases. [source] | ||||||||||||||||||||||||||||||||||