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Molecular Formula (molecular + formula)
Selected AbstractsFormaldehyde-releasers: relationship to formaldehyde contact allergy.CONTACT DERMATITIS, Issue 5 2010Formaldehyde-releasers in clothes: durable press chemical finishes. This is one of a series of review articles on formaldehyde-releasers and their relationship to formaldehyde contact allergy and in this paper formaldehyde-releasers used as durable press chemical finishes (DPCF) in textiles are discussed. The literature on allergy to DPCF since 1980 is presented in two parts. Part 1 (this article) presents a short historical overview of the problems with formaldehyde in clothes and discusses the chemistry of durable press chemical finishes, legislation in various countries, and studies on the amount of formaldehyde present in clothes. In addition, the DPCF that have caused contact allergy are presented with CAS, synonyms, molecular formula, chemical structure, applications, and patch test studies. In the forthcoming part 2, the frequency of sensitization to DPCF, occupational contact sensitization, relevance of patch test reactions, and relationship to formaldehyde contact allergy will be reviewed, followed by a discussion of both parts of the article together. [source] Syntheses, Crystal Structures and Magnetic Properties of Carboxylato-Bridged Polymeric Networks of MnIIEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 2 2006Subal Chandra Manna Abstract Three new carboxylato-bridged polymeric networks of MnII having,molecular formula [Mn(ox)(dpyo)]n (1), {[Mn2(mal)2(bpee)(H2O)2]·0.5(bpee)·0.5(CH3OH)}n (2) and {[Mn3(btc)2(2,2,-bipy)2(H2O)6]·4H2O}n (3) [dpyo, 4,4,-bipyridine N,N,-dioxide; bpee, trans -1,2 bis(4-pyridyl)ethylene; 2,2,-bipy, 2,2,-bipyridine; ox = oxalate dianion; mal = malonate dianion; btc = 1,3,5-benzenetricarboxylate trianion] have been synthesized and characterized by single-crystal X-ray diffraction studies and low temperature magnetic measurements. Structure determination of complex 1 reveals a covalent bonded 2D network containing bischelating oxalate and bridging dpyo; complex 2 is a covalent bonded 3D polymeric architecture, formed by bridging malonate and bpee ligands, resulting in an open framework with channels filled by uncoordinated disordered bpee and methanol molecules. Whereas complex 3, comprising btc anions bound to three metal centers, is a 1D chain which further extends its dimensionality to 3D via - and H-bonding interactions. Low temperature magnetic measurements reveal the existence of weak antiferromagnetic interaction in all these complexes. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Comparison of the hydrolytic stability of S -(N,N -diethylaminoethyl) isobutyl methylphosphonothiolate with VX in dilute solutionJOURNAL OF APPLIED TOXICOLOGY, Issue S1 2001M. D. Crenshaw Abstract The stability of S -(N,N -diethylaminoethyl) isobutyl methylphosphonothiolate,a V-type nerve agent developed by the former Soviet Union,in the environment is an important parameter in threat assessment analysis and for the determination of use, production, testing and storage of this chemical warfare agent. S -(N,N -Diethylaminoethyl) isobutyl methylphosphonothiolate is a structural isomer of the nerve agent VX developed by the USA and the UK and will be referred to as VXA (VX analog) in this presentation. Because VXA and VX differ structurally, even though they do have the same molecular formula, it is expected that their physical and chemical properties would be different. This preliminary investigation was undertaken to determine the relative hydrolysis rate of VXA compared with VX. The hydrolysis of each compound at approximately 1 mg ml,1 in unbuffered water at pH 7 was determined side-by-side. The half-lives for VXA and VX were determined to be 12.4 days and 4.78 days, respectively. Agent VXA hydrolyzed 2.6 times more slowly than VX, and each agent followed second-order hydrolysis kinetics. These results imply that VXA is more persistent in the environment and therefore poses a greater threat. These results also imply that VXA is more likely to be detected, if present, during an inspection in support of the Chemical Weapons Convention. Copyright © 2001 John Wiley & Sons, Ltd. [source] Mechanistic studies of branched-chain alkanols as skin permeation enhancersJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 3 2004Doungdaw Chantasart Abstract As part of a long-term effort to understand the structure/function relationship between chemical permeation enhancers and skin permeation enhancement, the present study examined the influence of hydrocarbon chain branching on the effectiveness of skin permeation enhancers of the type that possesses a polar group (e.g., the hydroxyl group) attached to a hydrocarbon chain(s). The effects of x -hexanol, x -heptanol, x -octanol, and x -nonanol (where x is the position of the hydroxyl group ranging from 1 up to 5) on the transport of a probe permeant, corticosterone, across hairless mouse skin (HMS) were investigated. Isoenhancement concentrations are defined as the aqueous concentrations for which different enhancers induce the same extent of permeant transport enhancement, E, across the lipoidal pathway of stratum corneum (SC). The isoenhancement concentrations of 2-alkanol, 3-alkanol, 4-alkanol, and 5-alkanol to induce E,=,10 were approximately 1.9-, 2.6-, 3.1-, and 3.9-fold higher, respectively, than those of the 1-alkanols of the same molecular formula. This suggested that the branched-chain alkanols have lower enhancer potency than the 1-alkanols of the same molecular formula; the potency decreases as the hydroxyl group moves from the end of the chain towards the center of the enhancer alkyl chain. To further investigate the mechanism(s) of action of the branched-chain alkanols as skin permeation enhancers, the equilibrium uptake of the enhancers into the hairless mouse skin stratum corneum (HMS SC) from aqueous enhancer solutions of E,=,10 was determined. The data from these experiments provided a direct measure of the "intrinsic" potency of the enhancer. In the same experiments, the equilibrium partitioning (distribution) of a surrogate permeant, estradiol (E2,), into the HMS SC was also determined and compared to the partitioning from PBS (no enhancer present). The uptake amounts (micromole/mg SC) for 1-alkanols into the intercellular lipids of the SC were found to be essentially the same at their isoenhancement concentrations. However, at their isoenhancement concentrations, the uptake amounts of the branched-chain alkanols into the intercellular lipids of HMS SC were higher than those of the 1-alkanols. These results support the view that: (1) the intrinsic potencies of the 1-alkanols are essentially the same and independent of their 1-alkyl chain length at their isoenhancement concentrations, (2) the intrinsic potencies of the branched-chain alkanols are lower than those of the normal alkanols, and (3) branching of the alkyl chain reduces the ability of the enhancer to effect lipid fluidization in the SC lipid lamellae at the target site(s). The enhancement effects of the branched-chain alkanols and the 1-alkanols at their isoenhancement concentrations upon E2, partitioning into the SC intercellular lipids were found to be approximately the same and in the range of five- to eight-fold enhancement. The constancy of this enhancement for E2, partitioning suggests that the mechanism of enhancement action for the branched-chain alkanols and the 1-alkanols are the same. Additionally, a good correlation of the intercellular lipid/PBS partition coefficients of both the branched-chain alkanols and the 1-alkanols with the n -octanol/PBS partition coefficients was found. This supports the view that the chemical microenvironment of the polar head group and the alkyl group of the studied enhancers at the site of skin permeation enhancer action in the SC lipid lamellae can be represented by water-saturated n -octanol for both the branched-chain alkanols and the 1-alkanols. © 2004 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 93:762,779, 2004 [source] Non-mathematical problem solving in organic chemistryJOURNAL OF RESEARCH IN SCIENCE TEACHING, Issue 6 2010David P. Cartrette Abstract Differences in problem-solving ability among organic chemistry graduate students and faculty were studied within the domain of problems that involved the determination of the structure of a molecule from the molecular formula of the compound and a combination of IR and 1H NMR spectra. The participants' performance on these tasks was compared across variables that included amount of research experience, year of graduate study, and level of problem-solving confidence. Thirteen of the 15 participants could be classified as either "more successful" or "less successful." The participants in this study who were "more successful" adopted consistent approaches to solving the problems; were more likely to draw molecular fragments obtained during intermediate stages in the problem-solving process; were better at mining the spectral data; and were more likely to check their final answer against the spectra upon which the answer was based. Experience from research, teaching, and course work were found to be important factors influencing the level of participants' success. © 2009 Wiley Periodicals, Inc. J Res Sci Teach 47:643,660, 2010 [source] Direct characterization of aqueous extract of Hibiscus sabdariffa using HPLC with diode array detection coupled to ESI and ion trap MSJOURNAL OF SEPARATION SCIENCE, JSS, Issue 20 2009Inmaculada C. Rodríguez-Medina Abstract The phenolic fraction and other polar compounds of the Hibiscus sabdariffa were separated and identified by HPLC with diode array detection coupled to electrospray TOF and IT tandem MS (DAD-HPLC-ESI-TOF-MS and IT-MS). The H. sabdariffa aqueous extract was filtered and directly injected into the LC system. The analysis of the compounds was carried out by RP HPLC coupled to DAD and TOF-MS in order to obtain molecular formula and exact mass. Posterior analyses with IT-MS were performed and the fragmentation pattern and confirmation of the structures were achieved. The H. sabdariffa samples were successfully analyzed in positive and negative ionization modes with two optimized linear gradients. In positive mode, the two most representative anthocyanins and other compounds were identified whereas the phenolic fraction, hydroxycitric acid and its lactone were identified using the negative ionization mode. [source] Rapid detection and characterization of reactive drug metabolites in vitro using several isotope-labeled trapping agents and ultra-performance liquid chromatography/time-of-flight mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 6 2009Timo Rousu Reactive metabolites are believed to be one of the main reasons for unexpected drug-induced toxicity issues, by forming covalent adducts with cell proteins or DNA. Due to their high reactivity and short lifespan they are not directly detected by traditional analytical methods, but are most traditionally analyzed by liquid chromatography/tandem mass spectrometry (LC/MS/MS) after chemical trapping with nucleophilic agents such as glutathione. Here, a simple but very efficient assay was built up for screening reactive drug metabolites, utilizing stable isotope labeled glutathione, potassium cyanide and semicarbazide as trapping agents and highly sensitive ultra-performance liquid chromatography/time-of-flight mass spectrometry (UPLC/TOFMS) as an analytical tool. A group of twelve structurally different compounds was used as a test set, and a large number of trapped metabolites were detected for most of them, including many conjugates not reported previously. Glutathione-trapped metabolites were detected for nine of the twelve test compounds, whereas cyanide-trapped metabolites were found for eight and semicarbazide-trapped for three test compounds. The high mass accuracy of TOFMS provided unambiguous identification of change in molecular formula by formation of a reactive metabolite. In addition, use of a mass defect filter was found to be a usable tool when mining the trapped conjugates from the acquired data. The approach was shown to provide superior detection sensitivity in comparison to traditional methods based on neutral loss or precursor ion scanning with a triple quadrupole mass spectrometer, and clearly more efficient detection and characterization of reactive drug metabolites with a simpler test setup. Copyright © 2009 John Wiley & Sons, Ltd. [source] Ring-Borylated 15-Electron and 17-Electron ansa -Chromocene Complexes, their Physical Properties and Molecular StructuresCHEMISTRY - A EUROPEAN JOURNAL, Issue 21 2007Pamela Abstract A detailed study of the thermal decomposition of the zwitterionic, ring-borylated ansa -chromocene hydrido carbonyl complex [Cr(CO)H{Me4C2(C5H4)[C5H3B(C6F5)3]}] (2) is described. This complex is formed in the reaction between [Cr(CO){Me4C2(C5H4)2}] (1) and B(C6F5)3 in toluene at ,78,°C. Above ,25,°C, 2 decomposes to a 50:50 mixture of the low-spin, 17,e CrIII complexes [Cr(CO){Me4C2(C5H4)[C5H3B(C6F5)3]}] (3,b) and [Cr(CO){Me4C2(C5H4)2}][HB(C6F5)3] (4). Carbon monoxide elimination from 3,b generates high-spin, 15,e [Cr{Me4C2(C5H4)[C5H3B(C6F5)3]}] (3,a), which coordinates two other electron-donating ligands, such as xylyl isocyanide, PMe3, and PPh2Me to form the low-spin, 17,e electron complexes 3,c, 3,d, and 3,e, respectively. High-spin, 15,e [Cr{Me4C2(C5H4)2}][HB(C6F5)3] (5) is generated by heating 3,b in toluene at 100,°C and periodically removing the evolved CO. Efforts to isolate more than a few X-ray quality crystals of 5 were thwarted by its tendency to form an insoluble precipitate (6) with the same molecular formula. Heating the solution of 5 at 120,°C results in its partial conversion (ca. 28,%) to 3,a, thereby allowing the formation of 3,a in yields as high as 74,% from the reaction between 1 and B(C6F5)3. The X-ray crystal structures of 3,b,e and 5 are described. Cyclic voltammetry measurements on 3,a,e reveal a dramatic reduction in the redox potentials of the complexes relative to their non-borylated analogues. DFT calculations show that this is due primarily to electrostatic stabilization of the oxidized species by the negatively charged borylate group. EPR and 19F,NMR spectroscopy allow 3,a to be distinguished from its Lewis base adducts 3,b,e and reveal the relative affinities of different Lewis bases for the chromium. [source] Differentiation of structural isomers in a target drug database by LC/Q-TOFMS using fragmentation predictionDRUG TESTING AND ANALYSIS, Issue 6 2010Elli Tyrkkö Abstract Isomers cannot be differentiated from each other solely based on accurate mass measurement of the compound. A liquid chromatography/quadrupole time-of-flight mass spectrometry (LC/Q-TOFMS) method was used to systematically fragment a large group of different isomers. Two software programs were used to characterize in silico mass fragmentation of compounds in order to identify characteristic fragments. The software programs employed were ACD/MS Fragmenter (ACD Labs Toronto, Canada), which uses general fragmentation rules to generate fragments based on the structure of a compound, and SmartFormula3D (Bruker Daltonics), which assigns fragments from a mass spectra and calculates the molecular formulae for the ions using accurate mass data. From an in-house toxicology database of 874 drug substances, 48 isomer groups comprising 111 compounds, for which a reference standard was available, were found. The product ion spectra were processed with the two software programs and 1,3 fragments were identified for each compound. In 82% of the cases, the fragment could be identified with both software programs. Only 10 isomer pairs could not be differentiated from each other based on their fragments. These compounds were either diastereomers or position isomers undergoing identical fragmentation. Accurate mass data could be utilized with both software programs for structural elucidation of the fragments. Mean mass accuracy and isotopic pattern match values (SigmaFit; Bruker Daltonics Bremen, Germany) were 0.9 mDa and 24.6 mSigma, respectively. The study introduces a practical approach for preliminary compound identification in a large target database by LC/Q-TOFMS without necessarily possessing reference standards. Copyright © 2010 John Wiley & Sons, Ltd. [source] Synthesis and NMR spectral study of some t(3)-aryl- r(2),c(4)-bisethoxycarbonyl- t(5)-hydroxy- c(5)-methylcyclohexanonesMAGNETIC RESONANCE IN CHEMISTRY, Issue 5 2005K. Pandiarajan Abstract Six t(3)-aryl- r(2),c(4)-bisethoxycarbonyl- t(5)-hydroxy- c(5)-methylcyclohexanones (6,11) were synthesized by condensing ArCHO (Ar = Ph, p -O2NC6H4, p -CH3OC6H4, p -ClC6H4, m -O2NC6H4 and m -C6H5O6H4) with ethyl acetoacetate in the presence of methylamine and their 1H and 13C NMR spectra were recorded. 1H,1H COSY and NOESY spectra were recorded for 6 and 7 and also HSQC and HMBC spectra for 6 and 8. Elemental analysis was carried out for all compounds. The mass spectrum was recorded for 8. All analytical data are consistent with the proposed molecular formulae. Analysis of NMR spectral data suggests that these compounds largely adopt chair conformations with the hydroxyl group occupying an axial orientation and all the other substituents occupying equatorial orientations. Long-range coupling (2,3 Hz) between the OH proton and the axial methylene proton at C-6 is observed in 6, 7, 8 and 11. Copyright © 2005 John Wiley & Sons, Ltd. [source] Characterization of protostane triterpenoids in Alisma orientalis by ultra-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 11 2010Xin Liu A reliable and sensitive ultra-performance liquid chromatography/quadrupole time-of-flight mass spectrometry (UPLC/Q-TOF-MS) method has been optimized and established for analysis of protostane triterpenoids in a commonly used traditional Chinese herbal medicine Alisma orientalis (Sam.) Juzep. The separation of crude extract of A. orientalis was achieved on a Waters ACQUITY HSS T3 column (100,mm,×,2.1,mm, 1.8,µm) eluting with 0.1% (v/v) formic acid/acetonitrile. A total of 20 protostane triterpenoids including 19 known compounds and a new one were well separated within 7,min. The collision-induced dissociation (CID) tandem mass spectrometric (MS/MS) fragmentation patterns of protostane triterpenoids was firstly reported in this study. The hydrogen rearrangement at the C-23-OH leads to dissociation of the bond between C-23 and C-24 in the protostane triterpenoid skeleton during the CID process. This dissociation was the characteristic CID fragmentation pathway of this class of triterpenoids, and was useful for further differentiation of some positional isomers which contain an acetyl unit on the C-23 or C-24 position. The identities of isolated compounds were identified by comparing their retention times and CID fragmentation behaviors with those of reference standards or tentatively assigned by matching the empirical molecular formulae with those reported in the literature. It is concluded that this newly established UPLC/Q-TOF-MS method is a powerful approach for structural elucidation of protostane triterpenoids isolated from A. orientalis. Copyright © 2010 John Wiley & Sons, Ltd. [source] A new approach to aid the characterisation and identification of metabolites of a model drug; partial isotope enrichment combined with novel formula elucidation softwareRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 2 2009Kirsten Hobby This work describes the identification of ,isotopically enriched' metabolites of 4-cyanoaniline using the unique features of the software package ,Spectral Simplicity'. The software is capable of creating the theoretical mass spectra for partially isotope-enriched compounds, and subsequently performing an elemental composition analysis to give the elemental formula for the ,isotopically enriched' metabolite. A novel mass spectral correlation method, called ,FuzzyFit', was employed. ,FuzzyFit' utilises the expected experimental distribution of errors in both mass accuracy and isotope pattern and enables discrimination between statistically probable and improbable candidate formulae. The software correctly determined the molecular formulae of ten previously described metabolites of 4-cyanoaniline confirming the technique of partial isotope enrichment can produce results analogous to standard methodologies. Six previously unknown species were also identified, based on the presence of the unique ,designer' isotope ratio. Three of the unknowns were tentatively identified as N-acetylglutamine, O-methyl-N acetylglucuronide and a putative fatty acid conjugate. The discovery of a significant number of unknown species of a model drug with a comprehensive history of investigation highlights the potential for enhancement to the analytical process by the use of ,designer' isotope ratio compounds. The ,FuzzyFit' methodology significantly aided the elucidation of candidate formulae, by provision of a vastly simplified candidate formula data set. Copyright © 2008 John Wiley & Sons, Ltd. [source] | ||||||||||