Studies of the Organic Reaction of Metal Carbonyl. X. The Oxo Reaction of Ethyl Acrylate—The Effects of the Reaction Conditions on the Distribution of the Products

Abstract

Abstract The ratio between the α- and β-carbethoxypropionaldehyde formed in the oxo reaction of ethyl acrylate is affected by various reaction conditions; the proportion of β-carbethoxypropionaldehyde increases with an increase in the reaction temperature, but decreases with an increase in the partial pressure of carbon monoxide or hydrogen. These effects can be explained on the basis of the reaction mechanism between cobalt hydrocarbonyl and ethyl acrylate (Y. Takegami et al., This Bulletin, 37, 1190 (1964)): in the first step of the reaction, ethyl acrylate reacts with cobalt hydrocarbonyl to give, selectively, α-carbethoxypropionylcobalt carbonyl (I), and then I isomerizes to β-carbethoxypropionylcobalt carbonyl (II). Accordingly, the rates of two competitive reactions, the isomerization of I to II and the reduction of I to the corresponding aldehyde, may be the factors determining the distribution of the oxo reaction products. Under the oxo reaction conditions, the isomerization of I to II seems to occur more easily at a relatively high temperature and to be prohibited by a high pressure of carbon monoxide. On the other hand, a relatively high pressure of hydrogen seems to be favorable to the reduction of I to the aldehyde.