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Simultaneous Reactions (simultaneous + reaction)
Selected AbstractsChemInform Abstract: Niobium(V) Chloride Catalyzed Synthesis of ,-Aminonitriles with Simultaneous Reaction of Aldehydes, Amines and Trimethylsilyl Cyanide.CHEMINFORM, Issue 47 2008Anjoy Majhi Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 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] FS01.2 Contact dermatitis to disperse blue 106 in PortugalCONTACT DERMATITIS, Issue 3 2004Francisco M Brandao Disperse blue 106 is one of the most important allergenic textile dyes. We reviewed all the patients that proved to be allergic to this dye, in 10 contact clinics, in Portugal, from 01/2000 to 06/2003. In the first 2 years disperse blue 106 was only tested in suspected cases, while in 2002/2003 it was routinely tested in our standard series. A total of 8957 patients (2797M + 6160F) were tested; fifty five patients (17M + 38F)(0.6%) were allergic to the dye, with a significant difference in incidence between the 2 periods (0.2 to 0.9%); a current relevance was found in 38 (69%) patients. In 5 patients the dermatitis was considered occupational. The main localizations were the axillae (25p), the antecubital fossae and the face (13p each), the neck (11p), the feet (8p), the hands and then trunk (7p each). Thirty six out of 44 patients (80%) that were tested with disperse blue 124 were allergic to this dye. Simultaneous reactions to PPDA and to fragrance mix were observed in 12 and 11 patients, respectively. Allergy to other dyes was found in 15 patients. Blouses and skirts were the main offending garments that induced contact allergy. Although both disperse blue 106 and 124 have been reported as frequent sensitizers, it proved not to be such an important allergen in Portugal. However, if tested routinely it can pick up some unexpected relevant allergic patients. [source] Block copolymers by chemoenzymatic cascade polymerization: A comparison of consecutive and simultaneous reactionsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 14 2006Matthijs de Geus Abstract The synthetic parameters for the chemoenzymatic cascade synthesis of block copolymers combining enzymatic ring-opening polymerization (EROP) and atom transfer radical polymerization (ATRP) in one pot were investigated. A detailed analysis of the mutual interactions between the single reaction components revealed that the ATRP catalyst system could have a significant inhibiting effect on the enzyme activity. The inhibition of the enzyme was less pronounced in the presence of multivalent ligands such as dinonyl bipyridine, which thus could be used in this reaction as an ATRP catalyst. Moreover, the choice of the ATRP monomer was investigated. Methyl methacrylate interfered with EROP by transesterification, whereas t -butyl methacrylate was inert. Block copolymers were successfully synthesized with this cascade approach by the activation of ATRP after EROP by the addition of the ATRP catalyst and, with lower block copolymer yields, by the mixing of all the components before the copolymerization. Adetailed kinetic analysis of the reactions and the structure of the block copolymers showed that the first procedure proceeded smoothly to high block copolymer yields, whereas in the latter a noteworthy amount of the poly(t -butyl methacrylate) homopolymer was detected. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4290,4297, 2006 [source] Oxidation and Volatilization of Silica Formers in Water VaporJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 8 2003Elizabeth J. Opila At high temperatures, SiC and Si3N4 react with water vapor to form a SiO2 scale. SiO2 scales also react with water vapor to form a volatile Si(OH)4 species. These simultaneous reactions, one forming SiO2 and the other removing SiO2, are described by paralinear kinetics. A steady state, in which these reactions occur at the same rate, is eventually achieved. After steady state is achieved, the oxide found on the surface is a constant thickness, and recession of the underlying material occurs at a linear rate. The steady-state oxide thickness, the time to achieve steady state, and the steady-state recession rate can be described in terms of the rate constants for the oxidation and volatilization reactions. In addition, the oxide thickness, the time to achieve steady state, and the recession rate also can be determined from parameters that describe a water-vapor-containing environment. Accordingly, maps have been developed to show these steady-state conditions as a function of reaction rate constants, pressure, and gas velocity. These maps can be used to predict the behavior of SiO2 formers in water-vapor-containing environments, such as combustion environments. Finally, these maps are used to explore the limits of the paralinear oxidation model for SiC and Si3N4. [source] Simultaneous sensitivity to fragrancesBRITISH JOURNAL OF DERMATOLOGY, Issue 5 2006D.A. Buckley Summary Background, Cinnamal/cinnamic alcohol and isoeugenol/eugenol are pairs of related fragrance chemicals found in Fragrance Mix I (FM I), and thus are routinely tested in combination with other fragrances in the European standard patch test series. Their close structural similarity makes the occurrence of simultaneous sensitivity within these chemical pairs likely, although at present there are no robust data to support this hypothesis. Objectives, To establish the frequency of simultaneous reactions to these fragrance chemicals in patients with suspected fragrance allergy attending a contact dermatitis clinic; to provide evidence in support of proposed metabolic pathways; and to determine whether including all four separately in FM I is necessary to avoid missing a diagnosis of fragrance allergy. Methods, We analysed retrospectively the records of patients patch tested to the European standard series during the 15-year period 1984,98 for positive reactions to FM I. In a subset of patients tested to the constituents of FM I, positive reactions to cinnamal, cinnamic alcohol, isoeugenol and eugenol were sought. Data were analysed using 2 × 2 contingency tables (Fisher's exact test). Results, During this period, 23 660 patients were tested to the European standard series, of whom 1811 (7·7%) had positive reactions to FM I. Of the 1112 patients tested to the constituents of FM I, 934 had positive reactions to at least one constituent (total 1324 positive reactions to constituents). Of these 934, 826 also had positive reactions to FM I itself; 108 were negative to FM I but reacted to one or more of its constituents. One hundred and seventy-eight patients did not react to any of the breakdown constituents of FM I; 34 of these had positive reactions to FM I itself. Of 139 patients allergic to cinnamic alcohol, 87 were also allergic to cinnamal (63%), compared with 108 (11·1%) of 973 cinnamic alcohol-negative patients (P < 0·00001). Of 231 patients allergic to isoeugenol, 50 were also allergic to eugenol (22%), vs. 109 (12·4%) of 881 isoeugenol-negative patients (P = 0·0002). Conclusions, These data support in vitro experiments indicating that cinnamal and cinnamic alcohol may generate a common hapten and are consistent with the view that simultaneous sensitization to isoeugenol and eugenol occurs to a limited extent, despite their being metabolized via different pathways. In view of the substantial number of isolated reactions to each of these fragrance chemicals, all four should continue to be included separately as constituents of FM I. [source] | |||||||||||||