Studies of the Organic Reaction of Metal Carbonyl. V. The Reaction of Cobalt Hydrocarbonyl with Olefin—The Effects of the Reaction Conditions and of the Structure of Olefin

Abstract

Abstract It has been observed that the reaction of 1-olefin with cobalt hydrocarbonyl is remarkably affected by the reaction conditions and by the structure of olefln. Some functional groups, such as the ester, n-butoxy and phenyl groups, adjacent to a C= C bond increase the reactivity of the C=C bond; the order of the reactivity is n-butyl vinyl ether, 103>styrene, 20>ethyl acrylate, 5>pentene-1. (The numbers indicate the relative reactivities, which have been roughly calculated from the gas absorption curve.) At a relatively low temperature (below 0°C), the α-carbon atom of the C=C bond of all these olefins except pentene-1 is selectively carbonylated; the reaction scheme may be considered to be as follows; suggesting that cobalt hydrocarbonyl is acting as an acid: (Remark: Graphics omitted.) However, these acylcobalt carbonyls with the branched structure isomerize to those with the straight one: (Remark: Graphics omitted.) A relatively high temperature (25°C) and a nitrogen atmosphere promote this isomerization considerably. The reverse isomerization seems to occur only with difficulty. On the other hand, these olefins mainly give the β-carbon carbonylated product at 25 °C, the formation of which seems to result from the two successive reactions, the carbonylation of the α-carbon atom and the isomerization of the corresponding acylcobalt carbonyl. However, the distribution of the products from pentene-1 is not affected by the reaction temperature. A relatively high pressure of carbon monoxide is advantageous for this reaction. Under a nitrogen atmosphere, some reaction other than the carbonylation seems to occur very rapidly, consuming a large part of the cobalt hydrocarbonyl used; a nitrogen atmosphere has an inhibitory effect on the carbonylation.