Secondary organic aerosol-forming reactions of glyoxal with amino acids.

Glyoxal, the simplest and most abundant alpha-dicarbonyl compound in the atmosphere, is scavenged by clouds and aerosol, where it reacts with nucleophiles to form low-volatility products. Here we examine the reactions of glyoxal with five amino acids common in clouds. When glyoxal and glycine, serine, aspartic acid or ornithine are present at concentrations as low as 30/microM in evaporating aqueous droplets or bulk solutions, 1,3-disubstituted imidazoles are formed in irreversible second-order reactions detected by nuclear magnetic resonance (NMR), aerosol mass spectrometry (AMS) and electrospray ionization mass spectrometry (ESI-MS). In contrast, glyoxal reacts with arginine preferentially at side chain amino groups, forming nonaromatic five-membered rings. All reactions were accompanied by browning. The uptake of 45 ppb glyoxal by solid-phase glycine aerosol at 50% RH was also studied and found to cause particle growth and the production of imidazole measured by scanning mobility particle sizing and AMS, respectively, with a glyoxal uptake coefficient alpha = 0.0004. Comparison of reaction kinetics in bulk and in drying droplets shows that conversion of glyoxal dihydrate to monohydrate accelerates the reaction by over 3 orders of magnitude, allowing these reactions to occur at atmospheric conditions.

catena-Poly[[[bis-(N,N-dimethyl-formamide)iron(II)]-{µ-2,2'-bis-(diphenyl-phosphino-yl)-N,N'-[(1R,2R)-cyclo-hexane-1,2-di-yl]dibenzamide}] bis-(perchlorate) N,N-dimethyl-formamide disolvate].

The title extended solid coordination compound, {[Fe(C(44)H(40)N(2)O(4)P(2))(C(3)H(7)NO)(2)](ClO(4))(2)·2C(3)H(7)NO}(n), was crystallized un-ex-pectedly from the reaction mixture containing the Trost ligand (1R,2R)-(+)-1,2-diamino-cyclo-hexane-N,N'-bis-(2'-di-phenyl-phosphinobenzo-yl) and Fe(ClO(4))(2)·6H(2)O in a 1:1 ratio in dimethyl-formamide (DMF) under reflux conditions. The polymeric complex is characterized by Fe(II) metal centers that are coordinated by two oxidized Trost ligands, each coordinated in a bidentate fashion in a square plane, along with two DMF mol-ecules above and below the plane [average Fe-O(DMF) = 2.086 (4) Å], forming an overall pseudo-octa-hedral geometry. The Trost ligand binds adjacent Fe(II) centers, each Fe(II) being bound through the O atom of one of the phosphine oxides [average Fe-O(PPh2) = 2.115 (4) Å] and the carbonyl O atom of the adjacent amide [average Fe-O(amide) = 2.192 (3) Å]. Disorder is observed in the co-solvated solvent: there are two DMF mol-ecules per Fe(II) centre, which were modeled as one DMF mol-ecule with complete occupancy and the other being modeled in two positions with equal occupancy. Disorder was also observed with one of the perchlorate anions, which was modeled in two positions with 0.75:0.25 occupancy.