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241.
242.
The degradation pathway of acylated homoserine lactone bacterial signaling molecules by oxidizing hypochlorite and stabilized hypobromite antimicrobials has been characterized. A reversed-phase HPLC separation using a cyano column was developed to detect the parent lactones, lactone-hydrolysis products, and halogenation products. Elucidation of the structures of the reaction products was done with the aid of online photodiode array UV spectroscopy and atmospheric pressure chemical ionization mass spectrometry. Quantitative output of the HPLC method was also used to estimate the kinetics of the degradation pathway. The results of this work found that only beta-keto-amide signal molecules are halogenated, where normal amide signals are not, and may represent one possible mechanism for control of industrial biofilms. 相似文献
243.
Casado J Ortiz RP Ruiz Delgado MC Hernandez V López Navarrete JT Raimundo JM Blanchard P Allain M Roncali J 《The journal of physical chemistry. B》2005,109(35):16616-16627
We report here the synthesis of three novel pi-conjugated heterocyclic mixed trimers that contain two electron-donating 3,4-ethylenedioxy-2-thienyl (EDOT) units covalently attached to a central proquinoid electron-accepting thienopyrazine moiety (two of these narrow-HOMO-LUMO gap D-A-D compounds also bear hexyl side chains attached either to the outermost alpha positions of the EDOT end rings or to the beta positions of the pyrazine fused ring). The modification of the terthiophene structure upon EDO, pyrazine, and hexyl substitutions has been treated in detail with spectroscopic and theoretical arguments. Solid-state properties reveal the occurrence of short intramolecular contacts between heteroatoms of adjacent rings. The analysis of the structure of the pi-conjugated backbone of each molecule is consistent with a partial quinoid-like pattern which partially reverts to be subtly more aromatic depending on the topology of the positive inductive effect of the hexyl chains. This quinoidization is a consequence of the appearance of a D(EDOT)-->A(PyT)<--D(EDOT) intramolecular charge transfer which further polarizes the structure. The same chemical concepts have been applied to address their electrochemical behavior. The three mixed trimers exhibit amphoteric properties due to the combination of electron acceptor and donor groups. Given their relative low HOMO-LUMO energy gap, these trimers promise to be good candidates for obtaining polymers with significant low energy gap combining electroactivity. 相似文献
244.
Summary A new carbon-hydrogen analyser is described. It differs from others in that it uses two specific infrared detectors. The basic principle of this analyser is a flash combustion of the sample in oxygen in a vertical furnace, and the water and carbon dioxide are measured with the two infrared detectors in series, the signals from the detectors being automatically integrated. The analyser determines carbon and hydrogen in petroleum products simultaneously in 3 min. The standard deviation for samples weighing about 1 mg is 0.3% for carbon (85%) and 0.06% for hydrogen (12%).
Presented at the 8th International Microchemical Symposium, Graz, August 25–30, 1980. 相似文献
Eine Schnellmethode zur gleichzeitigen Bestimmung von C und H in Erdölprodukten mit einem Infrarot-Detektor
Zusammenfassung Ein neues Gerät zur C-H-Bestimmung wurde beschrieben, das sich von bisher bekannten Apparaten durch zwei Infrarot-Detektoren unterscheidet. Die Probe wird im Sauerstoffstrom in einem senkrechten Rohr verbrannt, Wasser und Kohlendioxid werden nacheinander in zwei Infrarotgeräten gemessen. Die Detektorsignale werden automatisch integriert. Die Analysenzeit für Erdölprodukte beträgt ca. 3 min. Für Einwaagen von ca. 1 mg beträgt die Standardabweichung 0,30% für Kohlenstoff (85%) und 0,06% für Wasserstoff (12%).
Presented at the 8th International Microchemical Symposium, Graz, August 25–30, 1980. 相似文献
245.
Spino C Godbout C Beaulieu C Harter M Mwene-Mbeja TM Boisvert L 《Journal of the American Chemical Society》2004,126(41):13312-13319
(+)- or (-)-p-Menthane-3-carboxaldehyde is made in two easy steps from (+)- or (-)-menthone, respectively. This auxiliary allows for the synthesis of carbonyl compounds bearing a alpha-chiral quaternary carbon. The flexibility, efficiency, and ease of use of the method are demonstrated in a series of examples, which include the total synthesis of (+)-cuparenone as well as a partial synthesis of (-)-cassiol. 相似文献
246.
Anne Magali Layre Noëlle Martine Gosselet Estelle Renard Bernard Sebille Catherine Amiel 《Journal of inclusion phenomena and macrocyclic chemistry》2002,43(3-4):311-317
The ability of different cyclodextrins (CDs): CD, 2-hydroxypropyl CD to complex drugs like 3--hydroxy-11-oxoolean- 12-en-30-oic acid, 2-ethylhexyl-3-(4-methoxyphenyl)-2-propanoate and menthol was compared to that of water-soluble polymers: CD-co-epichlorhydrin polymer (pCD/EP) and CD-co-epichlorhydrin polymer partially modified with trimethylammonium groups (pCD/EPN+). 3--Hydroxy-11-oxoolean-12-en-30-oic acid was poorly solubilized by CD compared with other CD derivatives, however the determination of the complexation constants was possible for pCD/EP, K11 = 740, K12 = 4, for pCD/EPN+, K11 = 681, for CD, K11 = 16 and for hydroxypropyl CD, K11 = 114, K12 = 3.4. A significant increase of the solubility was observed for 2-ethylhexyl-3-(4-methoxyphenyl)-2-propanoate with all host molecules, it was 916 times its solubility in pure water with pCD/EPN+, 1116 and 1300 times with 2-hydroxypropyl CD and pCD/EP respectively. The association constants are K11 = 7970, K11 = 4700, K11 = 1470, K11 = 230 and K12 = 200 with pCD/EP, pCD/EPN+, CD, 2-hydroxypropyl CD respectively. An increase of the solubility of menthol was observed with all CD derivatives, up to 36–37 times, except for CD. The complexation constants are similar equal to about 200. 相似文献
247.
Ilhem Kaabi Tahar Douadi Djahida Haffar Salah Chafaa Magali Allain Mustayeen A. Khan Gilles M. Bouet 《Transition Metal Chemistry》2007,32(5):666-673
The crystal structure of a new symmetrical pentadentate N2O3 Schiff base: di[4-(phenylimino)pentan-2-one] ether (H2L) is described. In the solid state, the ligand appears as a keto-imine tautomer, while in DMSO solution, the eneamine form
is observed. This ligand coordinates cobalt(II), nickel(II), copper(II) and cadmium(II). The structures of these new complexes
are described using infrared and electronic spectroscopy, 1H-n.m.r. and d.s.c. The cyclic voltammograms of the ligand and the complexes in DMF are discussed. 相似文献
248.
Jankowski CK Allain F Dozol JF Virelizier H Tabet JC Moulin C Lamouroux C 《Rapid communications in mass spectrometry : RCM》2003,17(12):1247-1255
The extraction of (135)Cs from high activity waste arising from reprocessing of spent fuel can be achieved by using calix[4]arene crown compounds. The radiolytic degradation of calix[4]arene crowns as well as their solvent, o-nitrophenyloctyl ether (NPOE), was studied using electrospray ionization mass spectrometry (ESI-MS) (that formed Cs(+) or Na(+) adducts) in nitric acid, as well as by chemical ionization tandem mass spectrometry (MS/MS) experiments. The structures of major degradation products were identified with MS and specifically labelled nitric acid. Although NPOE and calix[4]arene crowns alone are relatively stable, under simulated conditions resembling the real industrial processes involving radiolysis in the presence of nitric acid, several products resulting from nitration and oxidation were observed. 相似文献
249.
A series of π-conjugated oligomers based on various combinations of thiophene, 3,4-ethylenedioxythiophene (EDOT) and thiophene-S,S-dioxide units have been synthesized. Theoretical calculations, optical and electrochemical data show that the relative positions of EDOT and S,S-dioxide units in the conjugated system exert strong influence on its electronic properties. The insertion of EDOT units inside the conjugated chain with the S,S-dioxide units located at the lateral positions leads to a planar conjugated system presenting moderate band gap. In contrast, substituted S,S-dioxide units located within the backbone produce a torsion of the conjugated chain. However, the twist angle is significantly reduced when the EDOT and S,S-dioxide moieties are separated by unsubstituted thiophene cycles. Introduction of S,S-dioxide unit in the median position of the chain has a stronger effect on the lowering of the LUMO level while insertion of EDOT units at the lateral positions limits the decrease of the HOMO level. Consequently, the corresponding oligomers present the smallest electrochemical gap while electrooxidation leads directly to the dication state through a bi-electronic process. 相似文献
250.
Robert J.P. Corriu Vijam Huynh Joël J.E. Moreau Magali Pataud-Sat 《Tetrahedron letters》1982,23(32):3257-3260
N,N-bis(silyl)enamines react with electrohiles in the presence of catalytic amounts of nucleophile. The reaction of carbonyl compounds catalyzed by fluoride ion provides an interesting route to 2?aza?1,3?dienes. The methoxide ion catalyzed reaction of N,N—dimethyl- formade gives rise to enamidines. 相似文献