STUDY OF PROTONATED METHANOL CLUSTER IONS UNDER THERMAL CONDITIONS

Size-dependent intracluster reactions within the methanol cluster system are studied using a fast flow reactor operated under thermal conditions. At low temperature, large protonated methanol cluster ions (CH3OH)(n)H+ (n up to 24) are produced for the first time under thermal conditions. Two mixed cluster ion series of (CH3OH)n(CH3OCH3)H+ and (CH3OH)n(H2O)H+ are also observed. Interestingly, the cluster ion patterns are found to be greatly influenced by the degree of solvation, due to several size specific intracluster ion-molecule reactions. The mixed cluster ions (CH3OH)n(CH3OCH3)H+ are observed only for the small clusters (n less-than-or-equal-to 5) while the mixed cluster ions (CH3OH)n(H2O)H+ are seen only for the large ones (n greater-than-or-equal-to 7). The work reported herein is particularly significant in that it demonstrates under thermal conditions, the influence of the degree of solvation on the course of intracluster ion-molecule reactions. Moreover, these new findings further support what is becoming a general observation concerning the role of the number of bonding sites in affecting the chemical nature of the ion core in mixed clusters.