Solvation of CH3NH2, CD3OD, and D2O molecules studied by temperature-programmed TOF-SIMS

On the basis of TOF-SIMS experiments, the thermally activated solvation and H/D exchange of hydrogen-bonded molecules, such as CH3NH2, CD3OD, and D2O, have been investigated. The D+(CH3NH2) ion is sputtered preferentially from the CH3NH2 molecule adsorbed on the D2O and CD3OD surfaces as a result of the proton transfer reaction during collisions of hydrogen-bonded neutral molecules. The CH3NH2 molecule adsorbed on the D2O surface undergoes a complete H/D exchange without mixing above 140 K, whereas the H/D exchange of CH3NH2 proceeds after mixing with the CD3OD matrix above 125 K. This behavior is interpreted in terms of the thermal diffusion of surface molecules as well as the hydrophilic and hydrophobic interactions between the functional groups. (C) 2003 Elsevier B.V. All rights reserved.