Cages formation

Two further unsaturated cages. Each of the systems discussed so far involves reaction of an electrophilic reagent with non-coordinated nucleophiles appended to metal-bound ligands. In contrast, in the following synthesis, cage formation occurs via an internal rearrangement of an Fe(u) complex of type (151) (Herron et al., 1982). Complexes of type (151) have already been discussed in Section 3.5. Treatment of these... 

An obvious difficulty in the cage model approach is the fact that there ought to be geometric limitations on the type of solutes which may enter the cages. Frank and Quist s theory should work well for small, nonpolar solutes, but larger solute molecules would present a difficulty. However, these authors do not imply that only specific, complete, pentagonal dodecahedra are involved in the cage formation in solution, but... 

Jones and Williams accidentally found a novel route to tetraarsacubane 10a when reacting 2-arsa-l,3-dionato lithium compound 111 with TaCls- A transient /-BuC=As is believed to play an important role in the cage formation (Scheme 35) <2004JOM(689)1648>. 

Published(8) and our own findings that sodalite cages in ZK-4 all contain one TMA suggest that the role is as a template for sodalite cage formation. Templating of sodalite cages apparently is not required for synthesis of zeolite A (Si/Al ratio of one) because the reaction is facile in the absence of TMA. 

Whereas Scheme 13.6 focuses on the kinetics of stereochemical changes to R)-3h induced by its photolyses. Scheme 13.7 focuses on regiochemical considerations of product formation. Scheme 13.7 links in-cage formation of 2-BN and 4-BN to specific, regio-isomeric radical pairs, [radical pair]2B and [radical pair]4B, and Equation 13.16 can be derived from it. 

Cyclodiene insecticides undergo the "cage formation" reaction to form their respective photoisomers (Figure 11.6). 

Tetrameric cage compounds with cubane structures have not been isolated. Tetramer formation is observed for [Mes A10]4 (34) in which the aluminum atoms remain three-coordinate and cage formation is precluded by the steric bulk of the Mes substituents. Compound (34) was prepared by reaction of [Mes AIH2]2 with [Me2SiO]3 and was not obtained by hydrolysis. 

This ordering of the water structure makes a negative contribution to the entropy of solution and in certain cases leads to a negative value of AS° in. In fact, this unfavorable entropy contribution resulting from cage formation could be an important reason why nonpolar solutes are insoluble in water. 

We have already encountered the effects of intermolecular forces in our discussion of precipitates and solubility. Here the intermolecular attractions between water molecules are instrumental in the ion-cage formation that allows some salts to go into aqueous solution. The glycerin molecule shares some similarities with water, but the individual glycerin molecules are still strongly attracted to each other and admit water to their ranks only when there is sufficient provocation. In this demonstration, the provocation occurs in the form of stirring, but no amount of stirring will force the canola oil into the glycerin solution until soap is added. 

Synthetic applications of [2 + 2] cycloadditions of a,)3-unsaturated carbonyl compounds are numerous. The synthesis of cubane (Eaton and Cole, 1964), in which cage formation is achieved by the following photochemical reaction step, is an example ... 

MECHANISM OF CAGE FORMATION DURING GROWTH OF CH4 AND Xe CLATHRATE HYDRATES A MOLECULAR DYNAMICS STUDY... 

Gas hydrates are crystalline forms of water that contain many gas molecule inclusions. Each gas hydrate has a unique molecular-scale structure in which a gas molecule is trapped by a cage structure consisting of H2O molecules. Until now, the thermodynamically stability and the structural properties of gas hydrates have been investigated for a lot of gas species by experimental studies. However, the growth mechanism of gas hydrates at the molecular scale, especially the mechanism of cage formation, is still poorly understood. This is because the molecular-scale growth mechanism of gas hydrates is complicated and difficult to elucidate experimentally. 

Recently, we carried out an MD simulation of the growth of a CH4 hydrate from a dilute aqueous CH4 solution at a temperature higher than 0 In this study, we also carried out an MD simulation of the growth of a Xe hydrate from a dilute aqueous Xe solution at a temperature higher than 0 °C. In this paper, we discuss the mechanism of cage formation during the growth of both CH4 and Xe hydrates, which were observed in those MD simulations. 

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