Ultrafast electron diffraction and direct observation of transient structures in a chemical reaction
Open Access
- 19 January 1999
- journal article
- research article
- Published by Proceedings of the National Academy of Sciences in Proceedings of the National Academy of Sciences
- Vol. 96 (2), 338-342
- https://doi.org/10.1073/pnas.96.2.338
Abstract
Ultrafast electron diffraction is a unique method for the studies of structural changes of complex molecular systems. In this contribution, we report direct ultrafast electron diffraction study of the evolution of short-lived intermediates in the course of a chemical change. Specifically, we observe the transient intermediate in the elimination reaction of 1,2-diiodotetrafluoroethane (C2F4I2) to produce the corresponding ethylene derivative by the breakage of two carbon–iodine, C—I, bonds. The evolution of the ground-state intermediate (C2F4I radical) is directly revealed in the population change of a single chemical bond, namely the second C—I bond. The elimination of two iodine atoms was shown to be nonconcerted, with reaction time of the second C—I bond breakage being 17 ± 2 ps. The structure of the short-lived C2F4I radical is more favorable to the classical radical structure than to the bridged radical structure. This leap in our ability to record structural changes on the ps and shorter time scales bodes well for many future applications in complex molecular systems.Keywords
This publication has 22 references indexed in Scilit:
- Femtosecond dynamics of transition states: the classical saddle-point barrier reactionsChemical Physics Letters, 1998
- Parameter Dependence in Continuum Electrostatic Calculations: A Study Using Protein Salt BridgesThe Journal of Physical Chemistry B, 1998
- Femtosecond Elimination Reaction DynamicsJournal of the American Chemical Society, 1997
- Clocking transient chemical changes by ultrafast electron diffractionNature, 1997
- Femtosecond X-ray Pulses at 0.4 Å Generated by 90° Thomson Scattering: A Tool for Probing the Structural Dynamics of MaterialsScience, 1996
- Structural and Vibrational Kinetics by Stroboscopic Gas Electron Diffraction: The 193 nm Photodissociation of CS2The Journal of Physical Chemistry, 1994
- Ultrafast Electron Diffraction. 5. Experimental Time Resolution and ApplicationsThe Journal of Physical Chemistry, 1994
- Conformational analysis. 15. 1,2-Dibromotetrafluoroethane and 1,2-diiodotetrafluoroethane. Electron diffraction investigations of the molecular structures, compositions, and anti-gauche energy and entropy differencesJournal of the American Chemical Society, 1992
- Radical brominations of alkyl bromides and the nature of .beta.-bromoalkyl radicalsAccounts of Chemical Research, 1984
- Least-squares refinement of molecular structures from gaseous electron-diffraction sector-microphotometer intensity data. I. MethodActa Crystallographica, 1964