Date on Honors Thesis

Spring 5-2025

Major

Chemistry

Minor

Biology

Examining Committee Member

Rachel J. Allenbaugh, PhD, Advisor

Examining Committee Member

Caleb B. Morris, PhD, Committee Member

Examining Committee Member

Kevin M. Miller, PhD, Committee Member

Abstract/Description

Palladacycles are a class of palladium complexes that show utility in catalyzing carbon-carbon cross coupling reactions. Mechanochemistry provides a greener alternative to synthesizing these palladacycles via repeated impacts that transfer mechanical energy into the reaction mixture, promoting formation of the desired complex. Specifically, liquid assisted grinding (LAG) has proven to be a viable tradeoff to neat mechanosynthesis of adding a small amount of liquid to decrease synthesis times or improve conversion. Some liquids actively participate in the reaction in a process termed as non-innocent LAG. This work focuses on the development of a mechanosynthetic method using non-innocent LAG for a palladacycle commercially known as Najera Catalyst II. This work will explore the effect that solvent properties such as donor number, acceptor number, and viscosity have on reaction conversion. Additionally, this work examines the kinetics of the formation of Najera Catalyst II, fitting the Johnson-Mehl-Avrami-Yerofeev-Kolmogrov (JMAYK), Finke-Watzky (FW), and First Order models to the collected conversion fraction data. Finally, a statistical analysis of the model fits is done to further elucidate the kinetics.

Twelve solvents were selected to be screened with varying donor numbers, acceptor numbers, and viscosities. These solvents included: acetonitrile, acetone, methanol, ethanol, tetrahydrofuran, 2-propanol, 2-phenylethanol, formamide, cyclohexanol, dimethylformamide, dimethyl sulfoxide, and pyridine. The solvent with the best performance was found to be formamide, with a conversion fraction of 0.77 after 600 minutes of milling. It was also found that middle range donor numbers, high acceptor numbers, and relatively low viscosities were best at promoting the formation of the complex.

Kinetic analysis of the synthesis of Najera Catalyst II found the rate constant, k, of the JMAYK model to be 6.103×10-3 min-1 and n to be 0.8464. For the FW model, the value of k1was 7.054×10-3 min-1 and k2' was -2.594×10-3 min-1. Finally, the value of k for the First Order model was 5.795×10-3 min-1. Coefficient of determination (R2) values for each model were as follows: 0.9558 for the JMAYK model, 0.9523 for the FW model, and 0.9486 for the First Order. As the FW and JMAYK models tend to fit data equally well, further statistical analysis was done which proves that the FW and First Order models fit equally well within experimental error. The evidence ratio was found to be 0.2901, which is between the upper and lower bounds of 104 and 10-4 to consider one model statistically a better fit than the other.

Creative Commons License

Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License
This work is licensed under a Creative Commons Attribution-NonCommercial-Share Alike 4.0 International License.

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