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Solvent response to fluorine-atom reaction dynamics in liquid acetonitrile
G T Dunning1, D Murdock, G M Greetham
1School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, UK. a.orr-ewing@bristol.ac.uk.
Physical Chemistry Chemical Physics : PCCP
|March 14, 2015
Summary
This study tracks hydrogen fluoride (HF) production in acetonitrile using time-resolved infrared spectroscopy. The evolving solvation environment of HF influences its vibrational band over several picoseconds after formation.
Area of Science:
- Physical Chemistry
- Chemical Kinetics
- Spectroscopy
Background:
- Understanding reaction dynamics in solution is crucial for chemical processes.
- Fluorine atom reactions are important in various chemical applications.
- Solvation dynamics significantly impact molecular properties and reaction pathways.
Purpose of the Study:
- To investigate the real-time production of hydrogen fluoride (HF) from fluorine atom reactions in liquid acetonitrile.
- To characterize the temporal evolution of the HF vibrational band and its relation to solvation.
- To determine the kinetics of HF formation and vibrational relaxation in solution.
Main Methods:
- Time-resolved infrared (IR) absorption spectroscopy was employed to monitor HF production.
- Femtosecond laser pulses (267 nm) initiated the reaction by photolyzing Xenon difluoride (XeF2).
- Broadband transient electronic absorption spectroscopy verified prompt F atom generation.
Main Results:
- The fundamental vibrational band of HF in acetonitrile spans over 400 cm(-1).
- Time constants for HF absorption rise increased at lower wavenumbers, indicating spectral evolution.
- Time constants for spectral growth at 3420, 3320, and 3240 cm(-1) were 3.04±0.26, 5.48±0.24, and 7.47±0.74 ps, respectively.
- Vibrational relaxation of initially excited HF occurred with a time constant of 2.4±0.2 ps.
Conclusions:
- The observed spectral shifts are attributed to the evolving micro-solvation environment of HF post-reaction.
- The study provides insights into the kinetics of HF formation and solvation dynamics in a liquid medium.
- Time-resolved IR spectroscopy is effective for probing rapid chemical events and solvation processes in solution.
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