Oligomerization of β-Propiolactone as a Model for the Formation of 2-Methyl Glyceric Acid Based Oligomers

Science Center, Bent Corridor

In the atmosphere, naturally emitted compounds can combine with human introduced pollutants to form compounds in SOA that are potentially harmful to animals and the earth’s climate. These compounds can affect cloud formation, the way aerosol particles interact with light, and are small enough to be inhaled by animals and cause health issues. Isoprene is one of the most common naturally emitted compounds in the atmosphere. Isoprene, itself a very volatile compound, can undergo reactions with human pollutants in the atmosphere that add functional groups, producing isoprene derived species that are less volatile and thus remain in the aerosol phase. 2-methyl glyceric acid (2-MG) is one such derivative of isoprene, and 2- methylglyceric acid based oligomers and related species have been observed in aerosol particles. Hydroxymethyl-methyl--lactone (HMML) has been proposed as a possible intermediate in the oligomerization reactions of 2-MG, however with no known synthesis process, a proxy lactone, -propiolactone (PL), must be used in order to study whether this hypothesis is feasible. Nuclear magnetic resonance spectroscopy techniques were used to analyze solutions with varying amounts of PL, PL’s hydrolysis product 3-hyrdoxy propionic acid (3-HP), and various inorganic ions commonly found in the atmosphere under varying pH conditions. The data collected was used to determine PL’s oligomerization mechanisms, the relative concentrations of products formed, and reaction lifetimes with the goal of determining whether HMML is a feasible intermediate in the formation of 2-MG based oligomers and related species.