ENVIRONMENTAL FATE OF METHYLCYCLOPENTADIENYL MANGANESE TRICARBONYL

摘要

Methylcyclopentadienyl manganese tricarbonyl (MMT) has been proposed as an octane booster for unleaded gasoline; such use could result in ecological and human exposure through surface water and groundwater ecosystems. To evaluate the environmental risks from MMT, its environmental fate constants and transformation pathways must be known. Constants for physical parameters that would likely influence MMT fate were collected from the literature or calculated; the compound's octanol/water partition coefficient and water solubility were determined in the laboratory. Experiments were designed to screen MMT for transformation pathways that are significant over environmentally short time frames. The MMT was found to be fairly stable in the dark in aquifer materials and sediments at various Eh levels; half-lives ranged from 0.2 to 1.5 years in aquifer materials at 25℃. (These matrices were not optimized for biodegradation.) On the other hand, MMT photolyzes rapidly in distilled water; its half-life in midday sunlight in water is approximately 1 min and the disappearance quantum yield is 0.13. Photodegradation products were identified as cyclopentadiene, methyl cyclopentadiene, carbon monoxide, and a manganese carbonyl that readily oxidized to trimanganese tetroxide.