The Mechanism of Pyridine Influence
on the Rates of Carbonylation Reactions

N. S. Imyanitov

All-Russia Research Institute of Petrochemical Processes, St. Petersburg, Russia

Received August 13, 1997

Abstract—This paper continues the discussion on the mechanism of the catalytic action of a pyridine–cobalt
carbonyl system and presents some arguments against catalysis by a compound with a hydrogen bond C₅H₅N ·
HCo(CO)₄. The reaction can be described by a number of steps in which pyridine accelerates the transformation
of intermediate acylcobalt carbonyl (“second-level” catalysis) and binds to a catalyst (cobalt hydrocarbonyl).
As the concentration of pyridine increases, a rate-limiting step is changed, and the dependence of the carbony-
lation rate on the concentration of pyridine is described by a curve with a maximum. For hexene-1 hydrocar-
boxylation and the reaction of octene-1 with carbon monoxide and ethylene glycol, a quantitative agreement
between the mechanism and the experimental data is shown.

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