We have shown in preceding papers(1–3), in a study of some specific anilinium ions such as φNH+3-n (CH3)n, φ2NH+2 and φ3NH+, that varying the ammonium groups, or the medium, can lead to great changes in the intensity of the secondary transition of the chromophore(1–4) because of a δ, π coupling involving the substituent (1–10) and φ. In the present work we should like to extend our experiments to more complex ions - since apart our own works the UV spectroscopy of the aniliniums is almost unknown - to study the sensitivity of the chromophore to long range interactions with X through space or through the bonds of the substituents(11–16). 相似文献
We study two types of generalized Baxter–Wu models, by means of transfer-matrix and Monte Carlo techniques. The first generalization allows for different couplings in the up- and down-triangles, and the second generalization is to a q-state spin model with three-spin interactions. Both generalizations lead to self-dual models, so that the probable locations of the phase transitions follow. Our numerical analysis confirms that phase transitions occur at the self-dual points. For both generalizations of the Baxter–Wu model, the phase transitions appear to be discontinuous. 相似文献
The ethylidene acetal of d-erythrose was used as a template for stereoselective IMDA reactions: high endo selectivity and yields in favor of the cis product were observed with 1,3,9-trienes, resulting from a boat transition state. For natural product synthesis, the reaction was successfully applied to a diene with terminal Z-olefin. 相似文献
We study the evolution, under convex Hamiltonian flows on cotangent bundles of compact manifolds, of certain distinguished subsets of the phase space. These subsets are generalizations of Lagrangian graphs, which we call pseudographs. They emerge in a natural way from Fathi's weak KAM theory. By this method, we find various orbits which connect prescribed regions of the phase space. Our study was inspired by works of John Mather. As an application, we obtain the existence of diffusion in a large class of a priori unstable systems and provide a solution to the large gap problem. We hope that our method will have applications to more examples.
RéSUMé. Nous étudions l'évolution, par le flot d'un Hamiltonien convexe sur une variété compacte, de certains ensembles de l'espace des phases. Nous appelons pseudographes ces ensembles, qui sont des généralisations de graphes Lagrangiens apparaissant de manière naturelle dans la théorie KAM faible de Fathi. Par cette méthode, nous trouvons diverses orbites qui joignent des domaines donnés de l'espace des phases. Notre étude s'inspire de travaux de John Mather. Nous obtenons l'existence de diffusion dans une large classe de systèmes à priori instables comme application de cette méthode, qui permet de résoudre le probleme de l'écart entre les tores invariants. Nous espérons que la méthode s'appliquera à d'autres exemples.
A new route to triethylenetetraamine selective mono-N-alkylation on secondary nitrogen atom using simultaneously bisaminal and diamide protections is presented and applied to the synthesis of poly-linear aza-ligands. 相似文献
The resolution of racemic 1-(3-methoxyphenyl)ethylamine with (S)-mandelic acid by diastereomeric salt formation can be made more economical by application of the Pope-Peachey method. This resolution was further improved upon by the addition of small amounts of a nucleation inhibitor, which prevents the formation of crystals of the more soluble diastereomer. The mandelic acid left in the solution is then used for further crystal growth of the less soluble diastereomer, furnishing high yields and diastereomeric excesses. Slow cooling and grinding of the crystals formed lead to increased secondary nucleation and thus to more consumption of the less soluble diastereomer and even better results. 相似文献