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21.
Thiophene sesquioxide is shown to be syn, endo-3a,4,7,7a-tetrahydro-4,7-epithiobenzo[b]-thiophene 1,1,8-trioxide (I) by 1 H and 13 C nmr evidence. Assignment of the 13 C spectrum was facilitated by a cross-ring long-range 13 C-1 H coupling. The mass spectrum of I is dominated by an unusual break-down to give benzene radical cation. 相似文献
22.
D R Perrott K Marlborough P Merrill T Z Strybel 《The Journal of the Acoustical Society of America》1989,85(1):282-288
Two experiments were conducted to examine the ability of human listeners to localize the "lag" or "echo" source in a precedence effect paradigm. A 5-ms noise burst was presented from a source located between 554-279 cm from the subject. This "lead" source was always located at 0 degrees azimuth. At the same time, one of two sources located at a distance of 610 cm from the subject was also activated with the same 5-ms noise burst. The subject's task was to identify which lag source had been active. Across sessions, the angular distance between the lag sources was varied, so as to allow a determination of the minimum audible angle (MAA) that could be resolved. Tests were run in a room designed to minimize reflections and in a hallway that was acoustically quite complex. No systematic differences in MAA thresholds were observed as a function of the environment employed. MAA thresholds obtained without the signal from the lead speaker were less than 1 degree for four of the five subjects tested. The precedence effect, as measured by the change in the MAA threshold, appears to have only a modest influence on localization performance. Under conditions in which the lead source was concurrently active, the thresholds were generally elevated by only 2 degrees-4 degrees. A reduction of this magnitude in the ability to resolve the position of the lag source does not seem to be sufficient, in itself, to account for the excellent localization performance frequently observed in reflective environments. 相似文献
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25.
Bach SB Sepeda TG Merrill GN Walmsley JA 《Journal of the American Society for Mass Spectrometry》2005,16(9):1461-1469
The dimeric complex of dibromo(ethylenediamine)palladium(II) observed in water was investigated using electrospray mass spectrometry. One microM aqueous solutions of Pd(en)Br2 yielded a variety of previously unreported species. The most abundant ion observed was attributable to the Pd(en)Br2.Pd(en)Br+ dimeric complex at m/z 568.7 (most abundant stable isotopes). The characteristics of the oligomeric complexes were examined using collision-induced dissociation (CID) up to MS6. The most common loss mechanism observed was loss of HBr leaving an unsaturated Pd(II) center. Fragmentation of the ethylenediamine ligand was also observed during CID experiments. Loss of Pd was only observed as the final step in the CID process when other loss mechanisms had been exhausted. A number of calculations were carried out at the B3-LYP/SBKJC[d] level of theory in an attempt to elucidate the structure of the [2M-Br]+ dimer. 相似文献
26.
Abstract In the butyllithium polymerization of butadiene in aliphatic solvents at 25°C, the first few monomer units are incorporated largely in a 1, 2 manner. With increasing degree of polymerization the extent of 1, 2 addition decreases to a limiting value of about 10% at a degree of polymerization of about 50. However, within this region of high 1, 2-addition increasing solvent basicity, i.e., changing from aliphatic to aromatic solvents, markedly reduces extent of 1, 2 addition and also narrows the molecular weight distribution. Further, in aliphatic solvents, increasing polymerization temperature from 25 to 60°C also results in a marked reduction in 1, 2 addition. These results are consistent with the concept that an ion pair of the associated organolithium complex, [R (n-1 Lin] ⊕R?, is the active polymerization species and that changes in mode of monomer incorporation are due to changes in the degree of association of the entire organolithium system. 相似文献
27.
A. Küntzel P. Chambard A. Ewald J. Wagner W. Schindler Th. Fasol L. Baens A. P. West A. B. Schachkeldjan P. Menaul E. Goux J. P. Berkmann D. Burton P. Vignon W. R. Atkin F. C. Thompson S. Sjablitzki J. H. Highberger D. L. Yonel L. Meunier Khoa Le Viet F. Stather R. Lauffmann H. G. Bennett M. Auerbach O. Gerngroß H. Herfeld W. Appelius R. Schmidt B. Pototschnig E. Stiasny L. Chièsa A. Boidin Fuld-Grosz Thomas-Weber Löhlein-Volhard E. Waldschmidt-Leitz J. Schneider A. Vlček Cl. Fermi E. Lenk M. Bergmann O. Dietsche R. Willstätter J. A. Wilson H. B. Merrill 《Analytical and bioanalytical chemistry》1934,96(1-2):56-76
28.
Akihiko Yoshikawa Stephan B. H. Bach Grant N. Merrill 《Journal of the American Society for Mass Spectrometry》2009,20(6):1015-1029
Dichloro(ethylenediamine)platinum(II), Pt(en)Cl2, was dissolved in H2O and D2O, and the resulting aqueous solutions were electrosprayed into a quadrupole ion-trap mass spectrometer. A series of major
and minor ionic hydrolysis products were detected. These ions were then subjected to collision-induced dissociation. As an
aid in interpreting the experimental results, density functional theory calculations were carried out. These computations
permitted the structures and energetics associated with the hydrolysis products to be determined. An understanding of the
hydrolysis of PtenCl2 and related coordination complexes is essential in the rational design of metal-based drugs. 相似文献
29.
Rivard E Merrill WA Fettinger JC Power PP 《Chemical communications (Cambridge, England)》2006,(36):3800-3802
A new class of heavier group 15 compounds demonstrating multiple bonding with boron has been synthesized using a simple donor-stabilization protocol. 相似文献
30.
Dougherty AM McDonald FE Liotta DC Moody SJ Pallas DC Pack CD Merrill AH 《Organic letters》2006,8(4):649-652
[structure: see text] A family of cyclic 1-deoxysphingolipid derivatives of structure 4 has been designed and synthesized, which may serve as tumorigenesis suppressors for various cancers. Compound 4 is a second-generation analogue developed from sphingosine (1), in which a hydroxyl substituent is moved from C1 to C5 and a methylene is added for conformational rigidity between the C2-nitrogen substituent and C4. The synthetic chemistry for pyrrolidine ring closure at C3-C4 features ring-closing metathesis followed by hydroboration-oxidation. 相似文献