The potential energy surfaces for the reactions of stable silylenes with carbon tetrachloride have been characterized in detail using density functional theory [B3LYP/6-311G(d)], including zero-point corrections. Five stable silylene species (1−5) have been chosen in this work as model reactants. The activation barriers and enthalpies of the reactions are compared to determine the relative reactivity of the stable silylenes on the reaction potential energy surface. Our theoretical findings suggest that stable silylene 5, which has two carbon atoms bonded to the silicon center and does not contain a resonance structure, is relatively unstable with respect to the reaction with haloalkanes, in comparison with the other stable silylenes (1−4). Of the three possible reaction paths, Cl abstraction (path 1), CCl 3 abstraction (path 2), and CCl 4 insertion (path 3), path 1 is found to be most favorable, with a very low activation energy and a large exothermicity. In short, electronic as well as steric factors play a dominant role in determining the chemical reactivity of the stable silylene species kinetically as well as thermodynamically. Furthermore, a configuration mixing model based on the work of Pross and Shaik is used to rationalize the computational results. The results obtained allow a number of predictions to be made.

The potential-energy surfaces of the cycloaddition reaction Cp(2)M+C60-->Cp(2)M(C60) (Cp=eta5-C(5)H(5); M=Cr, Mo, and W) were studied at the B3LYP/LANL2DZ level of theory. Two competing reaction pathways were found, which can be classified as [6,5] attack (path A) and [6,6] attack (path B). Given the same reaction conditions, the [6,6]-attack pathway for cycloaddition to C60 is more favorable than the [6,5]-attack pathway, both kinetically and thermodynamically. A qualitative model, based on the theory of Pross and Shaik, was used to develop an explanation for the reaction barrier heights. Thus, our theoretical findings suggest that the singlet-triplet splitting DeltaE(st) (=E(triplet)-E(singlet)) of the 16-electron d4 Cp(2)M and C60 species are a guide to predicting their reactivity towards cycloaddition. Our model results demonstrate that the propensity for cycloaddition to C60 increases in the order Cp(2)Cr

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Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal neoplasms of the gastrointestinal tract, and gastric adenocarcinomas are a common cancer worldwide. To differentiate GISTs from adenocarcinomas is important because the surgical processes for both are different; the former excises the tumor with negative margins, while the latter requires radical gastrectomy with lymph node dissection. Endoscopy with biopsy is used to distinguish GISTs from adenocarcinomas; however, it may cause tumor bleeding in GISTs. We reported here the confocal Raman microspectroscopy as an effective tool to differentiate GISTs, adenocarcinomas, and normal mucosae. Of 119 patients enrolled in this study, 102 patients underwent gastrectomy (40 GISTs and 62 adenocarcinomas), and 17 patients with benign lesions were obtained as normal mucosae. Raman signals were integrated for 100 s for each spot on the specimen, and 5 to 10 spots, depending on the sample size, were chosen for each specimen. There were significant differences among those tissues as evidenced by different Raman signal responding to phospholipids and protein structures. The spectral data were further processed and analyzed by using principal component analysis. A two-dimensional plot demonstrated that GISTs, adenocarcinomas, and normal gastric mucosae could be effectively differentiated from each other.

The potential energy surfaces for the formation, addition, and cycloaddition reactions of dialkylsilanechalcogenone (2) species have been studied using three levels of theories, i.e., B3LYP/ LANL2DZdp, CCSD theory, and Gibbs free energy (at the B3LYP level). Four dialkylsilanechalcogenone species with a SidX bond, where X = O, S, Se, and Te, have been chosen as model reactants in this work. Also, both MeOH addition and isoprene cycloaddition have been used to study the chemical reactivities of these species (2). The present theoretical investigations suggest that the relative reactivity of 2 increases in the order X = O < S < Se , Te. That is, the species with a less electronegative and a heavier chalcogen atom will have a smaller ΔE st , which facilitates its addition with MeOH and its cycloaddition reaction to isoprene. Furthermore, the singlet-triplet energy splitting, as described in the configuration mixing model attributed to the work of Pross and Shaik, can be used as a diagnostic tool to predict the reactivity of species such as 2. The results obtained are consistent with the available experimental observations and allow a number of predictions to be made.