Singlet-oxygen generation in the catalytic reaction of dioxiranes with nucleophilic anions.
Nucleophilic anions such as Cl(-), I(-), Br(-), t-BuO(-), O(2)(-) and OH(-) efficiently catalyze the decomposition of dimethyldioxirane (DMD) and methyl(trifluoromethyl)dioxirane (TFD). Singlet oxygen ((1)O(2)) is formed in these catalytic reactions, as demonstrated by the characteristic infrared chemiluminescence (IR-CL) at 1268 nm. The yield of (1)O(2) generation, measured by the IR-CL method, lies in the range between 2 and 98%, which depends on the particular anion employed. For the bromide ion, the catalytic decomposition of the dioxirane is in competition with the oxidation of Br(-) to elemental bromine.
Availability and reactivity of concentrated dimethyldioxirane solutions in solvents other than acetone
Abstract Four to five-fold increase in concentration or the possibility of isolation in “acetone-free” medium has become possible for dimethyldioxirane solutions in CH 2 Cl 2 , CHCl 3 , CCl 4 and CFCl 3 by employing a simple work-up procedure which involved washings with phosphate buffer. This procedure allowed the kinetics of the epoxidation of cis -stilbene to be studied and which were shown to follow a simple second order rate law for all solvents studied. The relative reaction rates were as follows: acetic acid > CHCl 3 > acetone > CCl 4 > toluene > ethyl acetate.
Determination of hydration equilibrium constants and pKa values of 4‐piperidones in buffered water solutions
1H and 13C chemical shift parameters are given for 4-piperidones and their derivatives in buffered aqueous solution. The 13C shift increments of methyl substituents on the nitrogen atom are discussed. The pH-shift dependence is studied in detail and pKa values are given for ketone forms and hydration products. The hydration equilibria are measured as a function of pH and temperature.