Graduate Program

Chemistry

Degree Name

Master of Science (MS)

Semester of Degree Completion

Spring 2019

Thesis Director

Rebecca A. Peebles

Thesis Committee Member

Edward M. Treadwell

Thesis Committee Member

Douglas G. Klarup

Thesis Committee Member

Daniel J. Sheeran

Abstract

Supercritical carbon dioxide (sc-C02) is a highly utilized industrial substance identified as an excellent solvent and a surfactant, which is cheaper and less hazardous than other typical solvents. The higher solubility of fluorinated hydrocarbons than their hydrocarbon (HC) analogs is not well understood and the theory behind the microsolvation of sc-C02 cannot be fully explained with the existing chemical information. Microwave spectroscopy is a good method of identifying the structural arrangement of clusters made from fluorinated HCs and C02. I n this project, microwave scans of the four different mixtures of 1 , 1-difluoroethene (DFE) and C02 were studied and additionally a pure DFE scan was studied additionally. A chirped-pulse Fourier-transform (FTMW) microwave spectrometer was used to obtain the scans. The DFE and C02 clusters can be easily identified using microwave spectroscopy because DFE is a very polar molecule and C02 has an induced dipole moment respectively. The relative intensities of the peaks in the scans and the rotational constants were considered to identify the molecular clusters. Previously identified DFE I C02 dimer structures were helpful to predict the bigger structures manually. Apart from that, the ABCluster application was used to predict the bigger structures, as guessing stable structures in three dimensions becomes harder as the cluster becomes bigger. All the predicted and approximated structures were optimized using Gaussian09W. One spectrum was identified in the DFE I C02 scans, and after comparing the intensities and rotational constants, it was confirmed as a DFE I (C02)3 tetramer. In this structure, one C02 is located above the DFE plane, another C02 is located side of DFE and the other C02 is located top-above of the DFE. One spectrum was identified in pure DFE scan and it was confirmed as a (DFE)3 trimer. In that structure, two DFEs are facing each other invertedly and the third DFE is located above the first two DFEs. This study aims to identify the salvation shell C02 makes around DFE when it dissolves. Hence, the maximum number of C02 molecules binding to a DFE molecule needs to be identified. A parallel study is occurring with vinyl fluoride (VF) I C02 and these studies collectively provide information about the variation in the number of C02 molecules that bind as the number of fluorine atoms attached to the same HC analog is varied. In the future, MathCAD applications will be used to identify largely spaced fingerprint patterns to find other stable clusters present in the experiment. Also, 13C isotopic studies will be done to confirm and compare the identified current structures.

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