Cycloketonization and linear polyketonization of ?, ?-dlcarboxylic acids

Abstract

1. Two reactions take place when the manganese salts of dicarboxylic acids are heated: cycloketonization and linear polyketonization. At 280–330° the first is almost the sole reaction for the adipate, while the second is almost the sole reaction for the sebacate; the suberate reacts in both directions. The salts of polyketodicarboxylic acids — the linear polyketonization products — also undergo decomposition, but at a higher temperature, forming complex mixtures which contain cyclic and aliphatic ketones. As a result, all of the cyclopentanone and the main portion of the cycloheptanone are obtained directly from the adipate and suberate; all of the cyclononanone and a small part of the cycloheptanone are formed from the salts of the polyketodicarboxylic acids. 2. A mechanism of the ketonization was proposed, which explains the reason for the changes in the ratios of the two reaction directions and the yields of cyclic ketones when the chain length of the unbranchedα,ω-dicarboxylic acids is increased.