Acid-base-coupled displacement

Besides the dependence of peak potential with solution pH, there is other evidence of the acid-base and redox coupling, namely the prediction of amine deprotonation during film oxidation. Deprotonation is a response to the creation of Os(III) sites that increment the concentration of positive charges in the film. This is an example of charge regulation a chemical equilibrium at the interface is displaced as the system tries to reduce its electrostatic charge. 

The probe compounds may be chosen as model acids (for example, carboxylic acids or chloroform) and bases (for example, pyridine or ether), with which to measure the acid-base character of the filler surface. However, the probes may be actual interfacial modifiers used in the composite system under investigation, for example an organosilane coupling agent or fatty acid dispersant. Furthermore other interesting interactions have been studied by the authors and include stabiliser - filler interactions during evaluation of controlled release/displacement effects. 

An even simpler protocol for performing nucleophilic substitutions (aminations) and Suzuki reactions in one pot was reported by the Organ group for the generation of a 42-member library of styrene-based nicotinic acetylcholine receptor (nAChR) antagonists (Scheme 6.21) [49]. After considerable experimentation, the authors found that simultaneous nucleophilic displacement and Suzuki coupling could be carried out very effectively by charging the microwave process vessel with the palladium catalyst (0.5 mol% palladium-on-charcoal), the boronic acid [R1B(OH)2], the... 

Illustrative examples of the acylation of support-bound amines with carbodiimides as coupling agents are listed in Table 13.3. Difficulties are usually encountered in the acylation of a-alkylamino acid derivatives (which are significantly less nucleophilic than simple secondary amines Entries 3 and 4) and Al-alkyl (Entries 5 and 6) or iV-aryl anilines. Acylations with haloacetic or related acids containing a leaving group prone to nucleophilic displacement should not be performed with the aid of HOBt and bases because O-alkylation of HOBt by the product occurs readily. 

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