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Alkane oxidation by the system ‘ tert ‐butyl hydroperoxide–[Mn 2 L 2 O 3 ][PF 6 ] 2 (L = 1,4,7‐trimethyl‐1,4,7‐triazacyclononane)–carboxylic acid’
Author(s) -
Kozlov Yuriy N.,
Nizova Galina V.,
Shul'pin Georgiy B.
Publication year - 2008
Publication title -
journal of physical organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.325
H-Index - 66
eISSN - 1099-1395
pISSN - 0894-3230
DOI - 10.1002/poc.1295
Subject(s) - chemistry , oxalic acid , adduct , cyclohexane , medicinal chemistry , acetonitrile , decomposition , catalysis , manganese , hydrolysis , reaction rate constant , alkane , kinetics , inorganic chemistry , organic chemistry , physics , quantum mechanics
The kinetics of cyclohexane (CyH) oxygenation with tert ‐butyl hydroperoxide (TBHP) in acetonitrile at 50 °C catalysed by a dinuclear manganese(IV) complex 1 containing 1,4,7‐trimethyl‐1,4,7‐triazacyclononane and co‐catalysed by oxalic acid have been studied. It has been shown that an active form of the catalyst (mixed‐valent dimeric species ‘Mn III Mn IV ’) is generated only in the interaction between complex 1 and TBHP and oxalic acid in the presence of water. The formation of this active form is assumed to be due to the hydrolysis of the MnOMn bonds in starting compound 1 and reduction of one Mn IV to Mn III . A species which induces the CyH oxidation is radical tert ‐BuO . generated by the decomposition of a monoperoxo derivative of the active form. The constants of the equilibrium formation and the decomposition of the intermediate adduct between TBHP and 1 have been measured: K = 7.4 mol −1 dm 3 and k = 8.4 × 10 −2 s −1 , respectively, at [H 2 O] = 1.5 mol dm −3 and [oxalic acid] = 10 −2 mol dm −3 . The constant ratio for reactions of the monomolecular decomposition of tert ‐butoxy radical ( tert ‐BuO . → CH 3 COCH 3 + CH 3 . ) and its interaction with the CyH ( tert ‐BuO . + CyH → tert ‐BuOH + Cy . ) was calculated: 0.26 mol dm −3 . One of the reasons why oxalic acid accelerates the oxidation is due to the formation of an adduct between oxalic acid and 1 ( K ≈ 10 3 mol −1 dm 3 ). Copyright © 2007 John Wiley & Sons, Ltd.