Catalytic Oxidative Deformylation of Polyethylene Glycols
with the Participation of Molecular Oxygen

A. M. Sakharov, L. I. Mazaletskaya, and I. P. Skibida

Emanuel Institute of Biochemical Physics, Russian Academy of Sciences, Moscow, 117977 Russia

Received January 11, 2000

Abstract—The kinetics of oxidation of diethylene glycol, triethylene glycol, and polyethylene glycols (PEGs)
with molecular weights ranging from 400 to 2000 in the presence of Cu(II) ions and bases was studied. It was
found that ethylene glycols can be oxidized by molecular oxygen in anhydrous media in a temperature range
of 30–60°C at anomalouosly high rates which are higher than the rates of chain-radical PEG autoxidation by
several orders of magnitude. Only terminal hydroxyl groups were subjected to oxidation. The reaction occurs
with the cleavage of a C–C bond and results in the formation of formic acid and a PEG with the number of
(CH₂CH₂O)– groups lower than that in the parent compound by unity. The rate and selectivity of PEG oxida-
tion were found to strongly depend on the molecular weight of the polymer; from diethylene glycol to
PEG2000, the specific rate of oxidation increased by a factor of 60 in terms of terminal hydroxyl groups. An
oxidation mechanism was suggested, which involves the formation of ternary complexes [Cu²⁺···A···O₂],
which undergo further degradation by a many-electron concerted mechanism to form formic acid and, probably,
an unstable hemiacetal {RO–CH₂OH}. The rapid oxidative degradation of the latter leads to the formation of
PEG with a lower molecular weight.

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