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121.
The decomposition of beta-amidozinc reagent 4 by beta-elimination has been shown to be a unimolecular process in both THF and DMF as solvent, with relative rates of 4:1 at room temperature, and activation parameters have been determined. These results indicate the beta-elimination is a syn-process. NMR experiments reveal that as little as 2 equiv of DMF can have a significant stabilizing influence on reagent 4. Use of a mixture of DMA and toluene as the bulk solvent, in place of DMF, has allowed successful palladium-catalyzed cross-coupling reactions of both 4 and the homologous reagent 5 with acid chlorides to yield unsymmetrical ketones (nine examples). 相似文献
122.
The rotational spectra of cis- and trans-1-hydroxynaphthalene and trans-1-DO-naphthalene have been recorded between 6 and 18 GHz using a pulsed microwave spectrometer. Most of the transitions detected are a type; hyperfine splittings from the electric quadrupole interaction were observed for some transitions of the deuterated isotopomer. The frequencies were well modeled with an S-reduced asymmetric rotor Hamiltonian. The rotational constants were determined much more accurately than previously. In addition, the quartic centrifugal distortion parameters were determined for the first time. Their values were very small, consistent with the rigid framework of this aromatic molecule. Theoretical calculations were carried out to support the assignment of the two forms to the cis and trans conformers. These calculations suggested that the cis conformer is slightly nonplanar in its equilibrium configuration, a property which is not inconsistent with its rotational constants. Copyright 1999 Academic Press. 相似文献
123.
M. Jackson G. R. Sudhakaran A. Silveira Jr. I. Mukhopadhyay R. M. Lees 《International Journal of Infrared and Millimeter Waves》1999,20(4):583-594
The high resolution Stark spectra of the singly deuterated methanol isotope, CH3OD, have been studied using the HCN laser with Stark fields up to approximately 60 000 V/cm. Numerous families of absorption lines have been observed in both parallel and perpendicular polarizations, resulting in the following assignments: with the 311 m line – J
K = 181 180
E
2,
t = 1; and with the 337 m line – J
k = 64 53
E
2,
t = 0 and J
K = 146 135
A,
t = 1. Zero-field frequencies for the assigned transitions are in agreement with Fourier transform measurements and those calculated from the available molecular constants. 相似文献
124.
P. G. Mendoza Jr. D. D. Jackson T. M. Niemczyk 《Journal of Radioanalytical and Nuclear Chemistry》1991,150(2):435-444
We investigated the plutonium assay method that uses the plutonyl trinitrate tetrapropyl-ammonium ion-pair solvent extraction with spectrophotometry of the extract as a candidate method capable of providing robustness and precision. To identify and assess the effect of factors on the precision, we looked at sampling techniques, silver oxide oxidation conditions extraction time, extract stability, and temperature dependence of the extract analytical peak height and position. We obtained a precision of 0.12%. 相似文献
125.
Michael C. Jackson 《The Journal of the Operational Research Society》1993,44(6):563-577
The emphasis in the social sciences has been on developing theory. The emphasis in OR has been on practice. It is argued in this paper that both traditions stand to gain much from close collaboration with each other. As a first step in this argument some highly relevant social science is introduced. As a second step, this is considered in relation to Beer's cybernetics and Checkland's soft systems methodology. These approaches demonstrate how subtle philosophical and sociological judgements can be incorporated in tools for practical action. At the same time, a much enhanced appreciation of the relative strengths of these methodologies is gained by viewing them from a social theory perspective. OR can help social scientists to make their findings usable in practice, and social science can help operational researchers achieve more sophisticated interventions and to learn from those interventions. 相似文献
126.
127.
(+)-Bis(methyl-1-naphthylphenylsilyl)mercury has been prepared, though probably in an optically impure state. Racemization without decomposition takes place at about 150°, and stereospecific cleavages of the Si—Hg bonds are possible. 相似文献
128.
We use the material of Parts I and II to obtain further results in sequence enumeration. These include the enumeration of sequences with respect to both maximal π1 and π2-paths, and the enumeration of sequences with distinguished substrings. We use the material to derive an enumerative proof of a generalization of a result of Foata and Schützenberger. Finally, we reconsider the enumeration of permutations with periodic pattern and show that the required generating function may be exhibited as the solution of a set of first-order nonlinear differential equations. Subsequent work has shown these to be matrix Riccati equations, although we refer to them here as Volterra equations. 相似文献
129.
130.
Landau parameters for nuclear matter are calculated for several Skyrme interactions. Resulting values of Go and G′o are in disgreement with empirical values and lead to instability against spin collapse in several cases. A suitable generalization of the interaction is suggested to overcome these difficulties. 相似文献