Super-stabilization

Super-Stabilization of -Conjugated Cations by Annelation to Bicyclic Frameworks... 

Our success in super-stabilization of cation 6 led us to the preparation of a higher homologue, that is, cyclooctatetraene (COT), fully annelated with BCO units 9 (9). As compared with a large number of studies on its radical anion or dianions, the studies on the cationic species of COT have been quite limited. There have been only one study by Olah and Paquette on the substituted COT dication (70), which is a typical 6n Hiickel aromatic system, and few sporadic studies on radical cations, which involve indirect spectral observations, such as electronic spectra in Freon matrix at low temperature (77,72) and constant-flow ESR study (13). 

As an example for the richness of enolate chemistry, consider this some enolates are much more stabilized than other enolates. These super-stabilized enolates are more tame nucelophiles (more selective in what they react with). For example, a compound with two carbonyl groups (separated by one carbon) can be deprotonated to form an intermediate that is sort of like a double enolate ... 

Structure-activity relationships have been probed by the use of EPR. Thus rate constants, determined by EPR linewidth analysis, were in good agreement with those obtained by optical spectroscopy. This method not only provides rate data but also provides structural features which may allow the determination of structure-activity relationships combining kinetic, structural, and steric factors. The rearrangement rates of a range of 2-aryl-3,3-dimethylmethylenecyclopropanes have been measured in order to calculate and determine s values for a range of substituents. A range of substituents named super stabilizers were identified (43). ... 

Neither methyl nor ethyl fluoride gave the corresponding cations when treated with SbFs. At low temperatures, methyl fluoride gave chiefly the methylated sulfur dioxide salt, (CH3OSO) ShF while ethyl fluoride rapidly formed the rert-butyl and ferf-hexyl cations by addition of the initially formed ethyl cation to ethylene molecules also formed ° At room temperature, methyl fluoride also gave the tert-butyl cation. In accord with the stability order, hydride ion is abstracted from alkanes by super acid most readily from tertiary and least readily from primary positions. 

Experiments showed that high methyl ester yields can be achieved with solid bases and super acids under moderate reaction conditions. The solid bases were more effective catalysts than the solid super acids. High stability can be achieved by an ordinary inexpensive preparation process, and the catalyst can be separated easily from the reaction products in the heterogeneous catalysis process. The costly catalyst removal process can be avoided compared with the homogeneous process. Therefore, the heterogeneous process using a solid catalyst should be more economical for biodiesel production. 

In summary, super-lattices may be obtained using the estabUshed techniques of self-organization but also a technique derived from molecular chemistry, the creation of hydrogen bond networks, hi addition, the crystallization of nanoparticles inside 3D super-crystals may be achieved using ionic stabilizers. 

A cement formulation, as indicated in Table 18-6, will be useful as a plugging solution in deep and super-deep wells [34] at temperatures of 100° to 160° C and in the presence of hydrogen sulfide. The solution has a high stability against hydrogen sulfide aggression. 

Silver(I) /3-diketonate derivatives have received significant attention due to the ease with which they can be converted to the elemental metal by thermal decomposition techniques such as metal organic chemical vapor deposition (MOCVD).59 The larger cationic radius of silver(I) with respect to copper(I) has caused problems in achieving both good volatility and adequate stability of silver(I) complexes for the use in CVD apparatus. These problems have been overcome with the new techniques such as super critical fluid transport CVD (SFTCVD), aerosol-assisted CVD (AACVD), and spray pyrolysis, where the requirements for volatile precursors are less stringent. 

The study of the stabilizing effect of the nitrone group in cumyl radical (205) (Scheme 2.72) (362) and cumyl cation (206) (Scheme 2.73) (363) has shown that the nitrone group appears to be a super radical stabilizer and, at the same time, a weak cation stabilizer. ... 

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