Metal-catalyzed hydroperoxide reactions. II. Molybdenum-catalyzed epoxidations of styrene and some substituted styrenes

Abstract

Hewlett-Packard No. 2801A quartz digital thermometer. Temperatures are believed accurate to +0.04°.Kinetic measurements for all of the thenils, with the exception of 3,3'-benzo[b] thenil, 2,2'-benzo[b]thenil, and 5,5'-di(2"thienyl)-2,2'-thenil, were carried out in the same manner.A sample of the thenil, in the range of 2.5-3.0 mmol, was weighed to 0.1 mg and placed in a 250-ml Teflon screw cap bottle, along with a magnetic stirring bar. The thenil was dissolved in 100.0 ml of equilibrated dioxane with stirring. The solution was continuously stirred during the kinetic run by means of a submersible magnetic stirrer mounted directly beneath the reaction vessel. A 50.00-ml quantity of 0.1 N temperature equilibrated potassium hydroxide solution was pipetted into the thenil solution with vigorous stirring. The vessel was sealed with a screw cap arrangement that permitted the insertion and withdrawal of a pipette. A 10.00-ml aliquot of the thenil solution was immediately withdrawn. The aliquot was quenched in a 10-ml sample of ice cold acetone and the clock was started.The sample was titrated to either a phenolphthalein (pH 8.3) or thymol blue (pH 8.0) end point with 0.01 N hydrochloric acid. At various intervals, depending on the rate of potassium hydroxide disappearance, 10-ml aliquots were withdrawn and titrated in the same manner.Simultaneously with the kinetic runs, a blank sample was determined under the same conditions described above, except that the thenil was omitted. In this manner it was possible to correct for any acidic impurity present in the thenil and also for any reaction of the base with the solvent. During the 80°runs and to a lesser extent at 70°, a small correction (by never more than 3%) was found to be necessary.At other temperature, the correction was too small to be measured.

Kinetics of epoxidation of alkyl esters of undecylenic acid: Comparison of traditional routes vs. ishii‐venturello chemistry

“…which can be integrated to get [5] where C p = concentration of peroxyacetic acid, C u = concentration of undecylenic acid or its ester, M = the molar ratio C p,0 /C u,0 at t = 0, X u = (C u,0 − C u )/C u,0 = the fractional conversion of undecylenic acid or its ester. Plots of ln[(M − X u )/M(1 − X u )] against time were made at 25 and 35°C (Fig.…”

“…Published work has shown that epoxidation of α-β-unsaturated acids has found greater attention than the terminally unsaturated acids, such as undecylenic acid and its ester. Among the numerous approaches available for epoxidation, the processes involving organic peroxyacids and hydroperoxides, such as cumene hydroperoxide (CHP), t-butyl hydroperoxide (TBHP) and ethyl benzene hydroperoxide (EBHP), are by far the most important (5).…”

Epoxidation of Styrene to Styrene Oxide: Synergism of Heteropoly Acid and Phase-Transfer Catalyst under Ishii−Venturello Mechanism

“…However, peroxy acids are hazardous to handle and the yields obtained by using them in the epoxidation of some industrially relevant compounds such as α-olefins are poor. On the other hand, organic hydroperoxides such as cumene hydroperoxide (CHP), tert -butyl hydroperoxide (TBHP), ethylbenzene hydroperoxides (EBHP), etc. , possess many advantages, including relative ease of handling and their higher reactivities. Acid labile epoxides of such compounds as styrene, α-methylstyrene, α-pinene, etc.…”

“…9 There are contradictory reports about the basic mechanism, and two schools of thought have emerged. According to the general concept of PTC, various steps in this system are given Duncan et al, 4 have not given any direct structure of any of the species PW 4 , PW 3 , and PW 2 except the comment that these species are capable of coordinating with quaternary cation Q + . Further, in the case of PW 4 , it is expected that three of the tungsten sites remain seven-coordinated and the fourth does not, meaning that the latter must find a ligand in the reaction mixture to obtain coordinate saturation.…”