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Subsequent Fragmentation (subsequent + fragmentation)
Selected AbstractsReactions of 2-Unsubstituted 1H -Imidazole 3-Oxides with 2,2-Bis(trifluoromethyl)ethene-1,1-dicarbonitrile: A Stepwise 1,3-Dipolar CycloadditionHELVETICA CHIMICA ACTA, Issue 7 2006Grzegorz Mlosto Abstract The reaction of 1,4,5-trisubstituted 1H -imidazole-3-oxides 1 with 2,2-bis(trifluoromethyl)ethene-1,1-dicarbonitrile (7, BTF) yielded the corresponding 1,3-dihydro-2H -imidazol-2-ones 10 and 2-(1,3-dihydro-2H -imidazol-2-ylidene)malononitriles 11, respectively, depending on the solvent used. In one example, a 1,:,1 complex, 12, of the 1H -imidazole 3-oxide and hexafluoroacetone hydrate was isolated as a second product. The formation of the products is explained by a stepwise 1,3-dipolar cycloaddition and subsequent fragmentation. The structures of 11d and 12 were established by X-ray crystallography. [source] Morphology and micromechanical properties of ethylene/1-octene copolymers and their blends with high density polyethylene,POLYMERS FOR ADVANCED TECHNOLOGIES, Issue 2-3 2005R. Adhikari Abstract The relationship between morphology and deformation behavior of selected ethylene/1-octene copolymers (EOCs) and their blends with high density polyethylene (HDPE) was investigated. The copolymers showed, depending on the 1-octene content, different morphologies ranging from lamellar to worm-like crystalline domains. The binary HDPE/EOC blends studied, which showed well phase-separated structures consistent with individual melting and crystallization behavior of the blend components, were characterized by a wide range of mechanical and micromechanical properties. The study of strain induced structural changes in an HDPE/EOC blend revealed that at large strains, the extensive stretching of the soft EOC phase is accompanied by rotation of lamellar stack along the strain axis and subsequent fragmentation of the crystals forming beaded-string-like structures. A significant depression in microhardness was observed in the copolymers. In their blends with HDPE, a deviation in microhardness behavior from the additivity law was observed. Copyright © 2005 John Wiley & Sons, Ltd. [source] A study of the elimination of water from lithium-cationized tripeptide methyl esters by means of tandem mass spectrometry and isotope labelingRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 20 2006Erach R. Talaty Extensive isotope labeling (2H, 13C and 15N), collision-induced dissociation (CID) and multiple-stage tandem mass spectrometry were used to investigate the elimination of H2O from a series of model, metal-cationized tripeptide methyl esters. The present results corroborate our earlier suggestion that loss of water from lithiated peptides is initiated by a nucleophilic attack from the N-terminal side upon an amide carbonyl carbon atom to form a five-membered ring as an intermediate followed by 1,2-elimination of water. We show that the nucleophilic atom is the oxygen atom of the N-terminal amide group in the fragmentation of [AcGGGOMe+Li]+ as well as [GGGOMe+Li]+. However, the subsequent fragmentation is markedly different in the two cases as a result of the absence and presence of a free amino group. In particular, extensive scrambling of protons in the , -positions of GGGOMe is observed, presumably as a consequence of intervention of the basic amino group. Copyright © 2006 John Wiley & Sons, Ltd. [source] A study of the electrospray ionisation and ion-trap fragmentation of [M,,,H], ions of new 3,5-disubstituted tetrahydro-2H -1,3,5-thiadiazin-2-thionesRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 10 2001Roberto Martínez-Alvarez The electrospray ionisation (ESI) in negative mode of the pharmacologically significant 3,5-disubstituted tetrahydro-2H -1,3,5-thiadiazin-2-thiones, and their subsequent fragmentations using an ion-trap mass spectrometer, have been investigated. Experiments on sequential product ion fragmentations (MSn) were performed in order to elucidate the degradation pathways for these compounds. The data presented show that the fragmentation of the even-electron [M,,,H], ions could proceed through an internal nucleophilic substitution displacement. Decarboxylation and extrusion of carbon disulfide are other fragmentations observed. Copyright © 2001 John Wiley & Sons, Ltd. [source] | ||||||||||