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91.
Hamilton SM Hopkins WS Harding DJ Walsh TR Haertelt M Kerpal C Gruene P Meijer G Fielicke A Mackenzie SR 《The journal of physical chemistry. A》2011,115(12):2489-2497
Far- and mid-infrared multiple photon dissociation spectroscopy has been employed to study both the structure and surface reactivity of isolated cationic rhodium clusters with surface-adsorbed nitrous oxide, Rh(n)N(2)O(+) (n = 4-8). Comparison of experimental spectra recorded using the argon atom tagging method with those calculated using density functional theory (DFT) reveals that the nitrous oxide is molecularly bound on the rhodium cluster via the terminal N-atom. Binding is thought to occur exclusively on atop sites with the rhodium clusters adopting close-packed structures. In related, but conceptually different experiments, infrared pumping of the vibrational modes corresponding with the normal modes of the adsorbed N(2)O has been observed to result in the decomposition of the N(2)O moiety and the production of oxide clusters. This cluster surface chemistry is observed for all cluster sizes studied except for n = 5. Plausible N(2)O decomposition mechanisms are given based on DFT calculations using exchange-correlation functionals. Similar experiments pumping the Rh-O stretch in Rh(n)ON(2)O(+) complexes, on which the same chemistry is observed, confirm the thermal nature of this reaction. 相似文献
92.
93.
John J. Orlando Geoffrey S. Tyndall Eric C. Apel Daniel D. Riemer Suzanne E. Paulson 《国际化学动力学杂志》2003,35(8):334-353
Rate coefficients and/or mechanistic information are provided for the reaction of Cl‐atoms with a number of unsaturated species, including isoprene, methacrolein ( MACR ), methyl vinyl ketone ( MVK ), 1,3‐butadiene, trans‐2‐butene, and 1‐butene. The following Cl‐atom rate coefficients were obtained at 298 K near 1 atm total pressure: k(isoprene) = (4.3 ± 0.6) × 10?10cm3 molecule?1 s?1 (independent of pressure from 6.2 to 760 Torr); k( MVK ) = (2.2 ± 0.3) × 10?10 cm3 molecule?1 s?1; k( MACR ) = (2.4 ± 0.3) × 10?10 cm3 molecule?1 s?1; k(trans‐2‐butene) = (4.0 ± 0.5) × 10?10 cm3 molecule?1 s?1; k(1‐butene) = (3.0 ± 0.4) × 10?10 cm3 molecule?1 s?1. Products observed in the Cl‐atom‐initiated oxidation of the unsaturated species at 298 K in 1 atm air are as follows (with % molar yields in parentheses): CH2O (9.5 ± 1.0%), HCOCl (5.1 ± 0.7%), and 1‐chloro‐3‐methyl‐3‐buten‐2‐one (CMBO, not quantified) from isoprene; chloroacetaldehyde (75 ± 8%), CO2 (58 ± 5%), CH2O (47 ± 7%), CH3OH (8%), HCOCl (7 ± 1%), and peracetic acid (6%) from MVK ; CO (52 ± 4%), chloroacetone (42 ± 5%), CO2 (23 ± 2%), CH2O (18 ± 2%), and HCOCl (5%) from MACR ; CH2O (7 ± 1%), HCOCl (3%), acrolein (≈3%), and 4‐chlorocrotonaldehyde (CCA, not quantified) from 1,3‐butadiene; CH3CHO (22 ± 3%), CO2 (13 ± 2%), 3‐chloro‐2‐butanone (13 ± 4%), CH2O (7.6 ± 1.1%), and CH3OH (1.8 ± 0.6%) from trans‐2‐butene; and chloroacetaldehyde (20 ± 3%), CH2O (7 ± 1%), CO2 (4 ± 1%), and HCOCl (4 ± 1%) from 1‐butene. Product yields from both trans‐2‐butene and 1‐butene were found to be O2‐dependent. In the case of trans‐2‐butene, the observed O2‐dependence is the result of a competition between unimolecular decomposition of the CH3CH(Cl)? CH(O?)? CH3 radical and its reaction with O2, with kdecomp/kO2 = (1.6 ± 0.4) × 1019 molecule cm?3. The activation energy for decomposition is estimated at 11.5 ± 1.5 kcal mol?1. The variation of the product yields with O2 in the case of 1‐butene results from similar competitive reaction pathways for the two β‐chlorobutoxy radicals involved in the oxidation, ClCH2CH(O?)CH2CH3 and ?OCH2CHClCH2CH3. © 2003 Wiley Periodicals, Inc. Int J Chem Kinet 35: 334–353, 2003 相似文献
94.
1-Fluoro-2-pyridone has been used to fluorinata selectively enamines and Grignard reagents under mild conditions. 相似文献
95.
96.
Suzanne T. Purrington T. Stephen Everett Carl L. Bumgardner 《Tetrahedron letters》1984,25(13):1329-1332
Malonates may be converted to esters containing an δ-CF3 group in a two-step process involving bromodifluoromethylation of the malonates followed by decarboxyalkylation-fluorination with fluoride ion in DMSO. 相似文献
97.
98.
In continuation of previous work, isomeric diazoester-substituted alkyltetrazoles 5 and 6 have been synthesized by the diazo-transfer method and studied in thermolysis reactions. Whereas the N-1 alkyl derivatives 5 give norcaradienes 7 in benzene solution and imidazotetrazoles 12 in acetonitrile, the more thermostable N-2 alkyl isomers 6 yield fluxional norcaradiene-cycloheptatriene systems, 10 – 11 , and ox-azoles 13. 相似文献
99.
Abstract— The isolation of a mutant, strain PM-9, of Rhodopseudonionus spheroides with an abnormal complement of carotenoid pigments is described.
PM-9 accumulates phytoene, phytofluene, ζ-carotene and neurosporene. Semi-aerobic cultures form more ζ-carotene and neurosporene relative to total carotenoids than do photo-synthetic cultures.
PM-9 is killed on exposure to light and oxygen.
By making use of the effect of oxygen on the nature of the carotenoids in PM-9, we have shown that these pigments do not directly influence the in vivo spectrum of bacteriochlorophyll.
Diphenylamine inhibits the synthesis of coloured carotenoids in Rhodopseudonionos gelatinosa but does not change the bacteriochlorophyll spectrum. 相似文献
PM-9 accumulates phytoene, phytofluene, ζ-carotene and neurosporene. Semi-aerobic cultures form more ζ-carotene and neurosporene relative to total carotenoids than do photo-synthetic cultures.
PM-9 is killed on exposure to light and oxygen.
By making use of the effect of oxygen on the nature of the carotenoids in PM-9, we have shown that these pigments do not directly influence the in vivo spectrum of bacteriochlorophyll.
Diphenylamine inhibits the synthesis of coloured carotenoids in Rhodopseudonionos gelatinosa but does not change the bacteriochlorophyll spectrum. 相似文献
100.
Charles S. Owen Pau Carango Susan Grammer Suzanne Bobyock Dennis B. Leeper 《Journal of fluorescence》1992,2(2):75-80
Carboxy-SNARF-1 is an emission-changing, pH-sensitive probe for measurements of intracellular pH. However, the protonated and deprotonated forms of the dye interact differently with intracellular constituents, and this imposes new requirements on the calibration of the system. Whole spectra of intracellular and extracellular C.SNARF-1 were analyzed and showed (1) intracellular quenching which was significantly greater for the deprotonated form of the dye than for the protonated state and (2) a detectable change in pK
a. Importantly for avoiding damage to cells, this mathematical analysis allowed reference spectra for fully protonated and fully deprotonated dye to be obtained without a need for spectra measured at extreme values of pH. It is not known what constituent(s) of the intracellular milieu might be responsible for the changes in dye behavior in the cell. To address this question, preliminary experiments with cell-free buffers compared the pattern seen inside the cell with quenching by a protein (bovine serum albumin; BSA) or that due to ethanol. The BSA result was completely unlike the intracellular case in that the protonated form of the dye was quenched. Buffer containing ethanol, on the other hand, was able to mimic the essential features of the intracellular spectra. 相似文献