As the population continues to balloon and severe drought persists in California, the demand for water reuse is higher than ever. Advanced water treatment processes associated with water reuse, specifically the disinfection of wastewater, have proven to aid in the formation of toxic disinfection byproducts (DBPs). Chloropicrin (THNM) is one of the most prevalent of these DBPs, but the reaction mechanism has not been fully elucidated. Understanding this reaction mechanism will aid in the prevention of chloropicrin formation in drinking water by identifying the chemical precursors of the compound. Previous research has proven that methylamine can be chlorinated to chloropicrin, and others have theorized that nitromethane is a key intermediate in the reaction, but its formation has not been experimentally determined. In this project, we’re primarily looking to quantify nitromethane for the chlorination of primary amines. Thus far, kinetic experiments have shown that methylamine is instantly transformed into nitromethane, and subsequently produces further chlorinated nitromethanes: monochloronitromethane, dichlornitromethane, and chloropicrin. These compounds were measured by GC-MS either via headspace sampling or ALS after liquid-liquid extraction with MtBE. As we look to the future of the project we’re hoping to further explore the reaction in various pH ranges, chlorination doses, and reaction times, as well as quantify other chlorinated nitromethane intermediates. We’re also planning to explore the chlorination of higher order amines such as isopropylamine and tertbutylamine.

Identification of a key intermediate in the reaction of chlorinating primary amines to chloropicrin

ACS Spring 2022

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