Atmospheric chemistry of 2-aminoethanol (MEA): reaction of the NH2(•)CHCH2OH radical with O2.

The alkanolamine 2-aminoethanol (NH(2)CH(2)CH(2)OH), otherwise known as monoethanolamine (MEA), is a widely used solvent for carbon capture, yet relatively little is known about its atmospheric chemistry. The hydroxyl radical initiated oxidation of MEA is thought to predominantly form the α-aminoalkyl radical NH(2)(•)CHCH(2)OH, which will subsequently react with O(2) in the atmosphere to produce a peroxyl radical. We have investigated the reaction of O(2) with the NH(2)(•)CHCH(2)OH radical using quantum chemical calculations and master equation kinetic modeling. This reaction is found to proceed predominantly via a chemically activated mechanism under tropospheric conditions to directly produce the imine 2-iminoethanol (NH═CHCH(2)OH) + HO(2)(•), with lesser amounts of the collisionally deactivated peroxyl radical NH(2)CH(O(2)(•))CH(2)OH. By largely bypassing a peroxyl radical intermediate, this process avoids ozone-promoting conversion of NO to NO(2) and makes the oxidation of MEA to 2-iminoethanol HO(x)-neutral overall. The imine product of MEA oxidation is proposed as an important intermediate in the formation of aerosols via uptake to water droplets and subsequent hydrolysis to ammonia and glycolaldehyde.