Evidence for the formation of clathrate structures of protonated waterndash;methanol clusters at thermal energy

摘要

Gas phase ionndash;molecule reactions of large protonated water clusters with methanol are studied in a flow reactor under thermal conditions. A distinct feature at H+(H2O)21corresponding to a stable clathrate structure is observed. Upon the addition of methanol from a reactant gas inlet, products of the general form H+(H2O)n(CH3OH)m(m=1ndash;5) are detected. Distinct features atn+m=21 are observed under different experimental conditions, which are indicative of the formation of clathratehyphen;like structures for mixed waterndash;methanol cluster ions. A switching reaction mechanism rather than an association is found to be operative. Considering the results of the present study and those from previous molecular beam experiments suggests that clathrate structures arise from their inherent stabilities rather than due to kinetic effects.