Thermochemical properties of solvated clusters

Laura Jane Haupert, Purdue University

Abstract

In the past, Cooks kinetic method has been used to determine the proton affinity of two body systems. In our studies, we use the kinetic method to determine the proton affinity of three body systems. Using this method we are able to measure the proton affinity of methanol dimer, benzene-water cluster, and aniline-water cluster. Once the proton affinity of the cluster is known, the neutral bond dissociation energy can be determined using a thermochemical cycle. Unfortunately, the bond dissociation energies of these clusters don’t agree with the expected values. The fragmentation patterns of these clusters maybe the cause for the discrepancy. A general understanding of the ion-molecule interactions in the gas phase provides insight into individual ion-solvent interactions in the condense phase. Gas phase studies provide an ideal medium for determining the important properties of clusters without solvent effects. For example, the binding first solvent molecule generally has the largest interaction between the solute and the solvent. As the extent of solvation increases, the similarities between clusters and the bulk phase also increases, eventually to the point where cluster exhibit many of the properties of bulk material. The hydration energies for protonated benzene and other aromatic ions, including protonated acetophenone, anisole, phenol and toluene were determined. In addition, we have remeasured the hydration energies for protonated aniline and benzonitrile to compare with previously measured values. Also, the solvation energies of benzene with protonated acetone, acetonitrile, dimethylether, formic acid, and methanol were determined. In addition, we have remeasured the solvation energy of protonated benzene-benzene to compare with the previously measured value.

Degree

Ph.D.

Advisors

Wenthold, Purdue University.

Subject Area

Molecular chemistry|Physical chemistry

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