Amine exchange into ammonium bisulfate and ammonium nitrate nuclei Department of Chemistry and Biochemistry, University of Delaware, Newark, DE, USA
Received: 10 December 2009 – Published in Atmos. Chem. Phys. Discuss.: 05 January 2010 Abstract. The exchange kinetics and thermodynamics of amines for ammonia in small
(1–2 nm diameter) ammonium bisulfate and ammonium nitrate clusters were
investigated using electrospray ionization Fourier transform ion cyclotron
resonance mass spectrometry (FT-ICR-MS). Ammonium salt clusters were reacted
with amine gas at constant pressure to determine the kinetics of exchange.
The reverse reactions, where aminium salt clusters reacted with ammonia gas,
were also studied, and no substitution of ammonia for amine was observed.
Gibbs free energy changes for these substitutions were determined to be
highly exothermic, −7 kJ/mol or more negative in all cases. Uptake
coefficients (reaction probabilities) were found to be near unity, implying
that complete exchange of ammonia in small clusters by amine would be
expected to occur within several seconds to minutes in the ambient
atmosphere. These results suggest that if salt clusters are a component of
the sub-3 nm cluster pool, they are likely to be aminium salts rather than
ammonium salts, even if they were initially formed as ammonium salts.
Revised: 29 March 2010 – Accepted: 07 April 2010 – Published: 16 April 2010
Citation: Bzdek, B. R., Ridge, D. P., and Johnston, M. V.: Amine exchange into ammonium bisulfate and ammonium nitrate nuclei, Atmos. Chem. Phys., 10, 3495-3503, doi:10.5194/acp-10-3495-2010, 2010.