Tunneling reactions of hydrogen addition to propene in a solid para-hydrogen matrix

Pullen, Gregory T.

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https://hdl.handle.net/2142/104382 Copy

Description

Title

Tunneling reactions of hydrogen addition to propene in a solid para-hydrogen matrix

Author(s)

Pullen, Gregory T.

Contributor(s)

• Lee, Yuan-Pern
• Haupa, Karolina Anna
• Douberly, Gary E.
• Franke, Peter R.

Issue Date

2019-06-21

Keyword(s)

Comparing theory and experiment

Abstract

We report the branching ratio for the H + propene tunneling reaction to form \textit{n}- or \textit{i}-propyl radicals within a solid \textit{para}-hydrogen (\textit{p}-\chem{H_2}) matrix at 3.2 K. Chlorine and propene are co-deposited in the \textit{p}-\chem{H_2} matrix, and then 365 nm and infrared light sources are used to produce HCl and free H atoms. These free H atoms can tunnel through the matrix until they encounter a propene molecule, at which point they can react to form either an \textit{n}-propyl or an \textit{i}-propyl radical. \textit{i}-Propyl was produced in greater proportion than \textit{n}-propyl, indicating that for hydrogen addition to the double bond, the rate of addition to the terminal carbon (\textit{i}-propyl) is faster than the rate of addition to the center carbon (\textit{n}-propyl). Because the barriers for addition are approximately 700 cm$^{-1}$ – 1500 cm$^{-1}$ (1000 K – 2000 K), the only available mechanism for reaction in the \textit{p}-\chem{H_2} matrix (3.2 K) is tunneling. \textit{Ab initio} calculations were used to compute the tunneling probabilities for the formation of the \textit{n}-propyl and \textit{i}-propyl radicals. The rate of addition to the terminal carbon (\textit{i}-propyl) was calculated to be faster, in agreement with experiment.

Publisher

International Symposium on Molecular Spectroscopy

Type of Resource

text

Language

eng

Permalink

http://hdl.handle.net/2142/104382

DOI

https://doi.org/10.15278/isms.2019.FF08

Copyright and License Information

Copyright 2019 Gregory T. Pullen

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