ISSN:
0947-3440
Schlagwort(e):
Kinetics
;
Hydrogen peroxide, activation of
;
Acid catalysis
;
Epoxidation
;
Cyclohexene
;
ET(30) values
;
Chemistry
;
Organic Chemistry
Quelle:
Wiley InterScience Backfile Collection 1832-2000
Thema:
Chemie und Pharmazie
Notizen:
The kinetics of the reaction of cyclohexene (CH) with an excess of H2O2 in acetonitrile (AN) at 293 K was studied at variable concentrations of H2O2 (1.7-13 M), water (1.6-13 M), acids HX (0.2-1.4 M), and salts NaX (0-1.7 M), with HX=HClO4, H2SO4, HNO3, HPF6, p-toluenesulfonic acid (TSAH), acetic acid (AH), trifluoroacetic acid (TFAH), and benzeneseleninic acid (BSAH). The solvent polarity parameter ET(30) of AN/water mixtures was determined. The oxidation of CH by H2O2, monitored by gas chromatography, was found to be acid-catalysed. The detailed investigation of the systems CH/HClO4/AN and CH/TSAH/AN showed that the reaction is first-order in CH according to [CH]=[CH]0 exp(-kexp·t). At [H2O2] ≤ 3 M, the experimental rate constant kexp could be approximated by kexp = k0[H2O2] + k·[H2O2]·[HX]2· [X-]tot·[H2O]-2, with k0 = (0.93 ± 0.7)·10-5 M-1s-1 and k = (9.65 ± 0.20)·10-3 M-2s-1 for HClO4 and k = (5.96 ± 0.10)·10-3 M-2s-1 for TSAH ([X-]tot = [NaX] + [HX]). GC analysis of the HClO4-catalysed reaction showed that trans-cyclohexane-1,2-diol (CHD) is a reaction product. The order of catalytic activity of the various acids HX, as derived from the size of kexp obtained under standard conditions, was found to be: AH ≪ HNO3 〈 TFAH 〈 TSAH 〈 HClO4 〈 HPF6 〈 H2SO4 〈 BSAH. A mechanistic interpretation is presented and the synthetic potential of the acid-catalysed oxidation of olefins by H2O2 is discussed.
Zusätzliches Material:
8 Ill.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1002/jlac.199719971222
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