Methyl Tert-Butyl Ether (MTBE), with the chemical formula C5H12O, is an organic compound that gained prominence as a fuel additive. Its structure, characterized by a tert-butyl group attached to a methoxy group, gives it unique chemical and physical properties that were advantageous for gasoline formulations. The molecular weight of MTBE is approximately 88.15 g/mol. Its relatively low boiling point (around 55-56°C) and high volatility were important for its function in gasoline, ensuring it vaporized efficiently during combustion.

One of MTBE's key attributes was its high miscibility with gasoline, allowing it to be blended seamlessly into fuel mixtures. This property, coupled with its excellent anti-knock capabilities, made it an effective octane enhancer. As an oxygenate, MTBE's molecular structure contains oxygen atoms, which, when introduced into gasoline, promote more complete combustion. This process reduces the formation of pollutants such as carbon monoxide and unburned hydrocarbons, thereby improving air quality. The flash point of MTBE is quite low, indicating its flammability, a characteristic common to many organic solvents and fuel components.

However, these chemical properties also contributed to its environmental challenges. MTBE's high solubility in water is a critical factor in its environmental behavior. Unlike many other hydrocarbons found in gasoline, which are less soluble and tend to form separate phases in groundwater, MTBE readily dissolves. This property allows it to spread quickly through aquifers once released, contaminating larger volumes of water. Furthermore, MTBE's resistance to natural biodegradation means that it persists in the environment for extended periods. While microbial degradation can occur under specific aerobic or anaerobic conditions, these processes are often slow and require particular microbial populations and environmental settings that are not universally present at contaminated sites.

The vapor pressure of MTBE also plays a role in its environmental fate, influencing its potential to volatilize from contaminated water or soil. Understanding the interplay of these chemical and physical properties – solubility, volatility, biodegradability, and chemical structure – is essential for predicting MTBE's behavior in the environment and for developing effective remediation strategies. The chemistry of MTBE thus provides crucial insights into why it became a significant environmental concern despite its utility as a gasoline additive.