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941.
942.
Carla Ferragina Patrizia Cafarelli Giorgio Perez 《Reaction Kinetics and Catalysis Letters》2002,77(1):173-179
a-Pinene isomerization was studied in gaseous and liquid phases on g-zirconium phosphate and rhodium g-zirconium phosphate. The first showed higher activity but lower reaction selectivity than the second, that led to tricyclic terpenes formation. 相似文献
943.
Giovanni Palumbo Michelangelo Parrilli Orsola Neri Carla Ferreri Romualdo Caputo 《Tetrahedron letters》1982,23(23):2391-2394
Disulfides are smoothly prepared from thiosulfonic S-esters by chlorotrimethylsilane and sodium iodide. In addition, thiosulfonic S-esters have been shown to be probable intermediates in other already known reactions leading to disulfides. 相似文献
944.
Umberto Bianchi Carla Cuniberti Enrico Pedemonte Corrado Rossi 《Journal of Polymer Science.Polymer Physics》1967,5(4):743-749
The Tian-Calvet microcalorimeter has been used to measure the heat of solution of atactic polystyrene in toluene at 30°C. By using a special technique for polymer sample preparation, it has been possible to measure directly the difference in conformational energy of the polystyrene chain at different temperatures, from 30 to 100°C. and to calculate its contribution to the specific heat. 相似文献
945.
Pasquarello C Sanchez JC Hochstrasser DF Corthals GL 《Rapid communications in mass spectrometry : RCM》2004,18(1):117-127
The synthesis and application of two new alkylating reagents, N-tert-butyl-2-iodoacetamide (N-t-butyliodoacetamide) and 2-iodo-N-phenylacetamide (iodoacetanilide), are described. N-t-Butyliodoacetamide and iodoacetanilide were synthesised to purity in their d(0)-light and in their respective d(9)- and d(5)-heavy forms. The newly synthesised reagents are covalently bound to peptides containing cysteines via an alkylation reaction. The mass differences of 5 and 9 Da avoid possible problems of overlapping isotope distribution. For each alkylated cysteine a peptide mass increases, respectively, by a multiple of 113 and 133 Da for the d(0)-light form of N-t-butyliodoacetamide and iodoacetanilide. These reagents can therefore replace common alkylating reagents in existing proteomics-based applications. Alkylated peptides increase in mass in the same mass range as amino acids and remain suitable for tandem mass spectrometry (MS/MS) data acquisition and analysis. The compounds are simple to use and derivatisation is based on widely applied alkylating procedures. Preliminary results show that these reagents can be applied for both protein quantitation and identification by peptide mass finger printing and/or MS/MS techniques. Using these chemicals and the suggested workflow enables the quantitative analysis of the whole protein sample and realises access to peptides that may contain potential post-translational modifications. Other approaches that incorporate a matrix-assisted laser desorption/ionisation (MALDI) interface prior to MS can take advantage of these chemicals, such as the molecular scanner. 相似文献
946.
Aragoni MC Arca M Caironi M Denotti C Devillanova FA Grigiotti E Isaia F Laschi F Lippolis V Natali D Pala L Sampietro M Zanello P 《Chemical communications (Cambridge, England)》2004,(16):1882-1883
Electrochemically monoreduced [M(R,R'timdt)(2)](-) dithiolenes, showing unprecedented wavelength selective photoconducting properties in the third optical fiber window (1500-1800 nm), fine-tunable through modifications in the chemical structure, allowed for the fabrication of a test photodetector with a bit rate of about 85 kbit s(-1). 相似文献
947.
948.
Experimental evidence has shown that a beverage containing Sunset Yellow FCF (labelled as E110 in the European Union), when exposed to natural conditions of summer temperature and sunlight, losses its colour. To possibly identify the degradation pathway and collect information on the potential toxicity of the uncoloured species formed, different degradation conditions, under both oxidising and reducing environments, were simulated in laboratory. Experiments were carried out under the following conditions: (i) thermally induced degradation, (ii) visible photo induced degradation, (iii) UV-photo induced conditions in oxidising environment (addition of hydrogen peroxide, Fenton reaction) and (iv) UV-photo induced conditions in reducing environment (addition of sulphide and ascorbic acid, addition of ascorbic acid in the absence and in the presence of saccharose). Decolourisation process was observed in oxidant conditions when applying the Fenton reaction but the reaction was too quick to be progressively followed. On the other hand, it was also possible to study the degradation reaction observed in reducing conditions in the presence of ascorbic acid. The HPLC-MS results gave evidence for the cleavage of the double bond and the protonation of the azo groups. The loss of colour is therefore not due to a mineralization process but to the formation of a dimeric form of 5-amino-6-hydroxy-2-naphthalene sulfonate and, likely, of p-amino-benzensulfonate. 相似文献
949.
The concept of "regioexhaustive substitution" has been successfully applied to 2-fluoro-, 2,3-difluoro-, and 2,5-difluoropyridine. All vacant positions were amenable to regioselective metalation and subsequent carboxylation by employing either chlorine as a neighboring site activating protective group or trimethylsilyl as a neighboring site screening protective group. In this way, approximately half a dozen fluorinated pyridinecarboxylic acids were derived from each starting material. 相似文献
950.
The discovery of a Byzantine church under the floor of one of the oldest churches of Salerno (Italy) has given us the opportunity to investigate the fine composition of the plaster through chemical and spectroscopic methods. In particular, considering that plasters are generally formed by a carbonate phase (carbonates) and an inert phase (silicates), the characterization, performed on the carbonate phase by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and thermogravimetric analysis (TGA), has revealed the presence of dolomite minerals. This information indicates that, during the building process, some accessory minerals of marble were added in the mortar to be used like fillers. The carbonate phase makes too difficult the spectroscopic characterization of the inert phase. Only by acid attack of the plaster the inert phase has been isolated and its characterization, by XRD and optical microscopy, has indicated the presence of olivine minerals and other typical silicates of river sands. 相似文献