Polystyrene Resin-Based Scavengers

Since the discovery of solid phase peptide synthesis in 1963 [4], the venerable polystyrene resin has remained the cornerstone of combinatorial chemistry over the years and continues to be utilized as the primary mode of support for immobilizing reagents and scavengers. This section briefly outlines the latest developments of resin-based scavengers. 

In addition to the silica or polymer based resins mentioned above, polymer based resins with specific chemistries at the functional group have also been widely used as palladium scavengers for synthetic organic reactions. These include macroporous polystyrene-bound trimercaptotriazine (TMT). It, along with the thiol resin, has been found to be highly effective in reducing the concentration of palladium in both aqueous and non-aqueous solutions [18]. 

Antioxidant an-te- ak-so-dont, ian- tI- (1926) n. A substance that slows down the oxidation of oils, fats, etc., and thus helps to check deterioration antioxidants are added commercially to foods, soaps, etc. Although the term technically applies to molecules reacting with oxygen, it is often applied to molecules that protect from any free radical molecule with unpaired electrons. Chemistry encyclopedia, www. ChemistryAbout.com. A substance incorporated in a material to inhibit oxidation at normal or elevated temperatures. Antioxidants are used mainly with natural and synthetic rubbers, petroleum-based resins, and other such polymers that oxidize readily due to structural unsaturation. However, some thermoplastics, namely polypropylene, ABS, rubber-modified polystyrene, acrylic and vinyl resins, also require protection by antioxidants for some uses. There are two main classes (1) Those inhibit oxidation by reacting with chain-propagating radicals, such as hindered phenols that intercept free radicals. These are called primary antioxidants or free-radical scavengers. (2) Those decompose peroxide into non-radical and stable products examples are phosphates and various sulfur compounds, e.g., esters of thiodipropionic acid. These are referred... 

Polystyrene supports modified with the similar triazine-based dendrons were used by Marsh et al. as insoluble scavengers for removal of excess nucleophilic or electrophilic reagents from the reaction mixtures. Dendrons, decorated with tertiary amines, effectively removed electrophiles (protons), whereas the similar resin with chlorotriazine terminal groups sequestered the excess nucleophiles (amines). 

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