Spectroscopic Studies of Intracluster Chemistry
Infrared predissociation spectroscopy of ion-solvent clusters has allowed us to examine the effects of sequential hydration on the reactivity of cations such as NO^+, NO_2^+, and protonated formaldehyde, H_2COH^+, stable gas phase ions which are known to undergo rapid reactions in aqueous solution. Our experiments demonstrate that these ions undergo hydration reactions at critical cluster sizes. The smaller clusters have spectra characteristic of H_2O ligans bound to stable ion cores, but as the cluster size increases, there is a sudden onset for intracluster rearrangements, e.g. NO_2^+ + H_2O yields H_3O^+ + HNO_3 which occurs upon hydration with four water molecules. With this approach, we can probe microscopic aspects of solvent effects on chemical reactions including the hydration of carbonyls and acid-catalyzed hydrolysis of amides.
© 1994 The International Society for Optical Engineering. SPIE. We acknowledge support of an NSF Presidential Young Investigator Award CHEM-8957423, E. I. DuPont de Nemours and Company, the Irvine Foundation, the Chevron Fund, an AT&T Special Purpose Grant, an NSF predoctoral fellowship for K.K., and the JPL Supercomputer Project for the computational studies. We are grateful to Maiy Frances Jagod for her heroic efforts in reprogramming the asymmetric rotor spectrum prediction program ASMWIR.
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