Pendant groups on polymers that have lower-critical solution temperature (LCST) properties experience a water-like environment below the LCST where the polymer is soluble but are less hydrated above the LCST when the polymer phase separates from solution. When these pendant groups are amphoteric groups like carboxylate salts or ammonium salts, the change in solvation that accompanies the polymer precipitation event significantly changes these groups' acidity or basicity. These changes in acidity or basicity can lead to carboxylate salts forming carboxylic acid groups by capturing protons from the bulk solvent or ammonium salts reverting to the neutral amine by release of protons to the bulk solvent, respectively. When polymers like poly(N-isopropylacrylamide) that contain a sufficient loading of such comonomers are dissolved in solutions whose pH is near the pK(a) of the pendant acid or basic group and undergo an LCST event, the LCST event can change the bulk solution pH. These changes are reversible. These effects were visually followed using common indicators with soluble polymers and or by monitoring solution pH as a function of temperature. LCST events triggered by the addition of a kosmotropic salt lead to similar reversible solution pH changes.

Thiylperoxyl radicals are the suggested reactive key-intermediates in the oxidation of bis-aromatic alkynes to alpha-diketones using molecular oxygen "activated" by thiyl radicals.

No abstract

The performance of thiyl radicals RS · in "self-terminating radical cyclisations" was explored. Using the medium-sized cyclodecyne (1) as model system, the reaction of PhS · generated by photolysis of (PhS) 2 was used to study the intermolecular S-radical addition and subsequent intramolecular radical translocations. This reaction resulted in the formation of three stereoisomeric sulfides 17a in very good yield, which all possess the bicyclo[4.4.0]decane framework with either cis and trans ring fusion. The isomeric bicyclo[5.3.0]decane framework was not formed. Product identification was performed using a combination of techniques, e.g. synthesis of authentic samples, X-ray analysis and computational studies of the potential energy surface, which also revealed valuable insight into the mechanism of this radical cyclisation cascade. The (PhS) 2 /PhS · system provides an efficient source for in situ