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151.
Sammakia T Johns DM Kim G Berliner MA 《Journal of the American Chemical Society》2005,127(18):6504-6505
The total synthesis of (+)-dihydrocompactin via an intramolecular ionic Diels-Alder reaction that proceeds with remote stereocontrol is described. This reaction proceeds by an intermediate vinyl-oxocarbenium ion (6), the conformational constraints of which lead to the observed asymmetric induction. The sense of asymmetric induction appears contrasteric and is explained by the proposed reactive conformation shown in Figure 1. 相似文献
152.
Hollingsworth KG Sederman AJ Buckley C Gladden LF Johns ML 《Journal of colloid and interface science》2004,274(1):244-250
Emulsion droplet sizing using pulsed field gradient (PFG) nuclear magnetic resonance (NMR) is a well-established technique. Traditionally these measurements require total acquisition times of typically 5-20 min per sample, which severely limits our ability to use this method to study dynamic processes. Here we present the application and verification of an NMR pulse sequence, Difftrain, which enables emulsion droplet size distributions to be measured in 3-10 s. We have previously introduced applications of Difftrain (C. Buckley, K.G. Hollingsworth, A.J. Sederman, D.J. Holland, M.L. Johns, L.F. Gladden, J. Magn. Reson. 161 (2003) 112-117), including the droplet sizing of a single unimodal emulsion sample. In this paper, several model emulsions containing different oils are measured and the results compared directly with sizing provided by laser scattering. In this manner, the Difftrain method is verified and its possibilities and limitations are explored. Guidelines are proposed for the range of droplet sizes for which accurate results can be produced. The Difftrain technique opens up the possibility of studying non-equilibrium emulsions; a study of the in situ emulsification of a 21% v/v water-in-silicone oil emulsion is presented. 相似文献
153.
The ν2 and ν3 fundamentals of FNO have been recorded with a Fourier transform spectrophotometer at an apodized resolution of approximately 0.004 cm?1. The Fourier infrared data have been analyzed together with previous microwave data to yield improved molecular parameters for the (000) and (010) vibrational states and the first set of constants for the (001) state. The main results (in cm?1) are
Ground state | |||
A | 3.1751882 (17) | 3.1861249 (12) | 3.1958722 (15) |
B | 0.39508266 (12) | 0.39407878 (14) | 0.39211484 (14) |
C | 0.35051504 (11) | 0.34899779 (16) | 0.34747411 (14) |
0 | 765.3551 (4) | 519.5980 (4) |