Molecular reactivity enhancement

Given that inner-sphere pathways are commonly encountered at metal-solution interfaces, as between reactants in homogeneous solution, a key question concerns the manner and extent to which the reactant-electrode interactions associated with such pathways lead to reactivity enhancements compared with weak-overlap pathways (Sect. 3.5.2). A useful tactic involves the comparison between the kinetics of structurally related reactions that occur via inner- and outer-sphere pathways. This presumes that the outer-sphere route yields kinetics which approximate that for the weak-overlap limit. For this purpose, it is desirable to estimate the work-corrected uni-molecular rate constant for the outer-sphere pathway at a particular electrode potential, k° , from the corresponding work-corrected measured value, kCOTr, using [cf. eqns. (10) and (13)]. 

In Ch. 5 Ceulemans reviews the protonation of alkanes in solid matrices by radical cations created by y-radiation, studied by EPR. The protonation does not take place at a particular atom but at a particular C-H or C-C bond, resulting in the formation of a three-center two-electron bond in a carbon-site specific way. Of great importance is the mobility of the matrix which greatly enhances the molecular reactivity. 

Reactivity enhancement by molecular traffic control - a consequence of released single-file constraints... 

J. M. Lehn and C. Sirlin (1978), Molecular catalysis Enhanced rate of thiolysis with high structural and chiral recognition in complexes of a reactive receptor molecule. Chem. Commun. 949-951. 

From transition metal complexes, molecular reactivity can be enhanced because of metal cation coordination that yields a particular structural ligand arrangement and, thus, destabilization of certain bonds not involved in the metal coordination. Conversely, the analyte converted to anionic form by attachment of a deprotonated mineral or organic acid reagent (X ) reflects either the presence of a labile proton site (but insufficiently acid... 

The key to solve problems of coarse morphology is to reduce interfacial tension in the melt and to enhance adhesion between the immiscible phases in the solid state. One solution is to select the most suitable blending technique so that co-continuous phase morphology can be obtained, which results in direct load sharing. The second solution is the addition of a third homopolymer or block or graft copolymer or low molecular reactive compounds, which is miscible with either of the two phases. This can be considered as non-reactive compatibilization. The third way is to blend suitably functionalized polymers, which are capable for specific interactions or chemical reactions (reactive compatibilization) [35],... 

Dicylopentadiene Resins. Dicyclopentadiene (DCPD) can be used as a reactive component in polyester resins in two distinct reactions with maleic anhydride (7). The addition reaction of maleic anhydride in the presence of an equivalent of water produces a dicyclopentadiene acid maleate that can condense with ethylene or diethylene glycol to form low molecular weight, highly reactive resins. These resins, introduced commercially in 1980, have largely displaced OfXv o-phthahc resins in marine apphcations because of beneficial shrinkage properties that reduce surface profile. The inherent low viscosity of these polymers also allows for the use of high levels of fillers, such as alumina tfihydrate, to extend the resin-enhancing, fiame-retardant properties for apphcation in bathtub products (Table 4). 

Bromine sulphate BrHS04 has been proposed as a possible molecular bro-minating species, since the catalysis by sulphuric acid of the bromination of benzoic acid by hypobromous acid was much greater than by perchloric acid of the same acidity198. Its reactivity was considerably less than that of H2OBr+ so that an enhanced rate spread is observed and its reactions only become noticeable with the least deactivated (i.e. most reactive) compounds employed in this particular study. 

Class 111-type behavior is the consequence of this impossibihty to create step-edge-type sites on smaller particles. Larger particles wiU also support the step-edge sites. Details may vary. Surface step directions can have a different orientation and so does the coordinative unsaturation of the atoms that participate in the ensemble of atoms that form the reactive center. This wiU enhance the activation barrier compared to that on the smaller clusters. Recombination as well as dissociation reactions of tt molecular bonds will show Class 111-type behavior. 

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