Oxidation of veratryl alcohol by molecular oxygen in aqueous solution catalyzed by cobalt salen-type complexes: the effect of reaction conditions

Mechanistic Insights into the Oxidation of Veratryl Alcohol with Co(salen) and Oxygen in Aqueous Media: An in‐situ Spectroscopic Study

“…[3,12] This reaction proceeds in the presence of molecular oxygen to reach TOF = 10-15 at optimum conditions (TOF = turnover frequency, moles of product per mol of catalyst per hour). [16] The effect of reaction conditions observed previously for this system suggest that a mononuclear superoxo complex is not responsible for catalytic activity. [16][17] However, direct proof for the intermediates involved in the catalytic cycle is lacking.…”

“…[16] The effect of reaction conditions observed previously for this system suggest that a mononuclear superoxo complex is not responsible for catalytic activity. [16][17] However, direct proof for the intermediates involved in the catalytic cycle is lacking. Temperature and pH have a dramatic effect on the catalytic activity of this system, and thus it is vital that the mechanism is studied under real experimental conditions.…”

“…[3,15] In this study, Co(salen) is used as a catalyst to oxidize a lignin model compound, veratryl alcohol (3,4-dimethoxybenzyl alcohol), to an aldehyde in alkaline water solution. Selective oxidation of lignin would be attractive for catalytic pulp bleaching [16][17][18] and for the search of renewable raw materials. [3,12] This reaction proceeds in the presence of molecular oxygen to reach TOF = 10-15 at optimum conditions (TOF = turnover frequency, moles of product per mol of catalyst per hour).…”

Aerobic Oxidation of Veratryl Alcohol to Veratraldehyde with Heterogeneous Ruthenium Catalysts

“…Quantitative conversion was, however, obtained with Cu-9,10-diamine-phenanthrene [27] as well as when using hexacyanoruthenate(II) in combination with either laccase or an electrolysis cell [28]. Several other catalyst systems based on Co, Cu or Ru salts have also been reported to provide VAld yields in the range 73-84% [29][30]. Despite excellent catalytic performance of many of the reported homogeneous catalyst systems they are inherently difficult to recover and recycle, which limit their general usability.…”

Co(Salen) Catalysed Oxidation of Synthetic Lignin-Like Polymer: Naoh Effects

“…These results confi rmed that NaOH is an important component of the reaction system for Co(salen) catalyzed-oxidation of lignin model polymer. This is because, in aqueous solutions, a hydroxide anion acts as an axial ligand that facilitates coordination with oxygen 26, 27 . In a study of the oxidation of 3,4-dimethoxybenzyl alcohol in aqueous alkaline media using Co(sulfosalen) as catalyst, Sippola and Krause 28 found that at higher pH, more of the phenolic OH groups were deprotonated to more easily oxidised phenolates, which is another reason for the more easily degradation of lignin model polymer by Co(salen) when NaOH was added to the reaction system.…”