Liquid-Phase Oxidation Kinetics of Phenyl-<i>Gem</i>-Dichlorocyclopropane
Roducts based on gem-dichlorocyclopropyl-ketone are promising syntons for the production of biologically active and medicinal compounds. A possible approach to its synthesis can be the liquid-phase oxidation of a styrene derivative, phenyl-gem-dichlorocyclopropane, with decom-position of the intermediate hydroperoxide according to a known scheme. Using kinetic methods on an automated manometric unit with constant regulation of oxygen pressure with computer registration, the kinetics of phenyl-gem-dichlorocyclopropane oxidation initiated by azobisisobutyronitrile has been studied (1). The initiation rate was determined using a known inhibitor of radical chain oxidation of a -tocopherol. Using the modern DFT method M06-2X / MG3S, calculations of the bond dissociation energy are carried out. This method allows determining the bond strength with high accuracy (~1.5 kcal.mol-1). It was established that under the conditions studied (60°C, the initiator is AIBN, Wi = 5.3 . 10-8 mol (lЧs)-1), the initiated oxidation of compound 1 proceeds via a radical-chain mechanism with a quadratic chain break. This is confirmed by the fact that the oxidation rate ( W 0) does not depend on pressure in the range of 90-100 kPa and is directly proportional to concentration 1 and the square root of the initiation rate. The obtained value of the oxidizability parameter for 1 is k 2. k 6-0.5 = 5.10-5 (60 оС). The rate constant for the continuation of the chain k 2 is estimated. The bond strengths calculated by the M06-2X / MG3S method are consistent with the values obtained. Thus, the obtained values of k 2. k 6-0.5 and k 2, as well as the calculated strength values of the tertiary C-H bonds in compound 1 indicate that the corresponding hydroperoxide from 1 cannot be formed in sufficient concentration (in 24 hours at 60 оC its yield does not exceed 0.1%).