排序方式: 共有22条查询结果,搜索用时 0 毫秒
1.
2.
The Feynman path integral Monte Carlo approach has been coupled to the gauge including atomic orbital formalism in order to analyse the absolute magnetic shieldings of the benzene nuclei under the conditions of thermal equilibrium. The Hamiltonian employed in the derivation of ensemble averaged NMR quantities is of the Hartree-Fock type. The basis set used is of 6–31G quality. The spatial delocalization of the atoms leads to a deshielding of both types of benzene nuclei relative to the shieldings experienced at the minimum of the potential energy surface. This deshielding has to be traced back to bond length elongations in thermal equilibrium. The influence of the nuclear fluctuations on the NMR parameters of benzene is quantum driven up to temperatures of 400 K; classical fluctuations are of minor importance in this low-temperature window. 相似文献
3.
4.
5.
6.
The use of ionic liquids as aids for microwave heating of nonpolar solvents has been investigated. We show that hexane and toluene together with solvents such as THF and dioxane can be heated way above their boiling point in sealed vessels using a small quantity of an ionic liquid, thereby allowing them to be used as media for microwave-assisted chemistry. Using the appropriate ionic liquid, the heating can be performed with no contamination of the solvent. To show the applicability of the system, two test reactions have been successfully performed. 相似文献
7.
We show that using water in conjunction with microwave heating it is possible to prepare aryl nitriles from the corresponding aryl iodides rapidly and in high yield without the need for a palladium catalyst. 相似文献
8.
Leadbeatera NE Torenius HM Tye H 《Combinatorial chemistry & high throughput screening》2004,7(5):511-528
Due to their extraordinary properties, such as the ionic composition, good thermal stability, low vapor pressure, and solution interactions, ionic liquids can be used as solvents, reagents, and heating aids in conjunction with microwave chemistry. Synthesis of diverse molecules can be improved with the use of the ionic liquids assisted microwave heating due to fast reaction times, simple reaction work-up, and catalyst recovery. This mini-review outlines this newly emerging field. 相似文献
9.
10.