Carbon Suboxide, a Highly Reactive Intermediate from the Abiotic Degradation of Aromatic Compounds in Soil

The formation of volatile compounds during abiotic degradation processes of aromatic compounds in soil has been the subject of many experimental studies but should be examined further. In this context, the present work investigates the natural formation of carbon suboxide using the model compounds catechol and 3,5-dichlorocatechol and also a soil sample from a peat bog. The measurements were performed with a purge and trap GC/MS system following various optimization steps. Under certain conditions, we obtained 16.7 ng of carbon suboxide from a 250 mg soil sample. We also found that the formation of carbon suboxide requires a definite activation energy and that it is rather short-lived in the natural environment. A subsequent reaction to malonic acid is expected in the presence of water. It is shown that iron(III), hydrogen peroxide, and chloride are prerequisites for its formation. Experimental parameters for the highest yield of carbon suboxide depend on the precise molecular structure of the model compound or on the individual soil sample, respectively. The presented results point to a new degradation process for aromatic compounds in soil.