Rare theoretical calculations

Inter- and intramolecular hydrogen bondings are also important for the formation of epoxytwinol A (71), which would be produced by the quite rare formal [4 -I- 4] cycloaddition reaction. Theoretical calculations suggest that preassociation... 

Figure 3 Energy of the quasi-free state in rare gas fluids as a function of density. Solid lines represent recent results obtained by field ionization for Ar [61], Kr, and Xe [see Eq. (6)] [63]. Recent theoretical calculations are shown for Ar by the dashed lines [64] and for Ar, Kr, and Xe by the dotted lines [65].

Hope et al. (116) presented a combined volumetric sorption and theoretical study of the sorption of Kr in silicalite. The theoretical calculation was based on a potential model related to that of Sanders et al. (117), which includes electrostatic terms and a simple bond-bending formalism for the portion of the framework (120 atoms) that is allowed to relax during the simulations. In contrast to the potential developed by Sanders et al., these calculations employed hard, unpolarizable oxygen ions. Polarizability was, however, included in the description of the Kr atoms. Intermolecular potential terms accounting for the interaction of Kr atoms with the zeolite oxygen atoms were derived from fitting experimental results characterizing the interatomic potentials of rare gas mixtures. In contrast to the situation for hydrocarbons, there are few direct empirical data to aid parameterization, but the use of Ne-Kr potentials is reasonable, because Ne is isoelectronic with O2-. 

The following paragraph deals with the experimental approach to the degradation mechanism of different molecules and with the role of the diluent. Theoretical studies related to stability remain rare, and calculations were often performed on pure ligands in the gas phase, thereby omitting the important role of surrounding solutes. 

Theoretical calculations on the rare earth oxide systems using an intermediate coupling scheme show good agreement with experimentally observed spectra [18,19]. 

In view of the matrix-isolation infrared studies, the theoretical calculations, and those studies of aluminum beam-water reactions, it is of considerable interest to probe the electronic structure of aluminum metal atom hydration reaction intermediates and products Isolated in rare-gas matrices. Such a study will form a useful adjunct to the infrared research. A mapping of the electronic structure of these species will provide a data set to which further theoretical calculations may compare. A more focused elucidation of the nature of the gas-phase aluminum hydration reaction s chemiluminescent continuum emitter may be provided... 

One of the rare NH-pyrazoles which is liquid at room temperature is 3(5)-methylpyrazole (11). The pure liquid is probably a 50 50 mixture of both tautomers in solution <92JOC3938> (the same conclusion is true for 3(5),4-dimethylpyrazole <90JA1303 . The inclusion of the compound in a host affords a 1 1 1 complex of the host with both tautomers present in the crystal. This has allowed the determination of the x-ray structure of (11a) and (11b) simultaneously <88CL106l>. Theoretical calculations at the 6-31G //6-31G level (see Section 3.01.2.1) on 3(5)-methylpyrazole (11) lead to the conclusion that 3-methyl tautomer (11a) is slightly more stable than 5-methyl tautomer (11b) by 0.4 kcal mol <89MI 30l-oi>. Moreover, the 3-methyl tautomer appears to be more acidic and more basic than the 5-methyl one. 

A summary of potential parameters obtained from scattering measurements and theoretical calculations on the H+-rare gas systems... 

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