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Chemical Ionization of TNT and RDX with Trimethylsilyl Cation

Crellin, Kevin C. and Widmer, M. and Beauchamp, J. L. (1997) Chemical Ionization of TNT and RDX with Trimethylsilyl Cation. Analytical Chemistry, 69 (6). pp. 1092-1101. ISSN 0003-2700. doi:10.1021/ac961003q.

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Fourier transform ion cyclotron resonance mass spectrometry has been used to examine the reactions of Si(CH_3)_3+ with nitrobenzene, TNT, and RDX. With nitrobenzene, the only reaction observed is adduct formation which generates the C_6H_5NO_2Si(CH_3)_3+ ion. The bimolecular rate constant for the reaction of Si(CH_3)_3+ with nitrobenzene is measured to be 1.8 × 10^(-9) cm^3 s^(-1)molecule^(-1). With TNT, fragmentation and adduct formation were observed. The bimolecular rate constant for the reaction of Si(CH_3)_3+ with TNT is measured to be 0.85 × 10^(-9) cm^3 s^(-1) molecule^(-1). With RDX, the dominant reaction observed is adduct formation, but some fragmentation is seen as a minor reaction pathway. The bimolecular rate constant for the reaction of Si(CH_3)_3+ with RDX is estimated to be similar to that observed with TNT (∼0.7 × 10^(-9) cm^3 s^(-1) molecule^(-1)). Collision-induced dissociation experiments performed on both the TNT−Si(CH_3)_3+ and the RDX−Si(CH_3)_3+ adducts using off-resonance collisional activation show the same fragmentation pattern that is observed during adduct formation. This fragmentation pattern appears to be a “fingerprint” for both adducts. These reactions appear to be driven by the high affinity of Si for oxygen and the attraction of the Si(CH_3)_3+ ion to the formal negative charge of oxygen in a nitro group. A reaction coordinate diagram for reactions of RDX with Si(CH_3)_3+ is derived (from known thermochemistry and ab initio calculations on the reactive intermediates) and its implications are discussed. Reactions of this type could be useful as a detection scheme for common explosives.

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Beauchamp, J. L.0000-0001-8839-4822
Additional Information:© 1997 American Chemical Society. Received for review October 1, 1996. Accepted December 13, 1996. Publication Date (Web): March 15, 1997. We acknowledge the Federal Aviation Administration for support of this work under Grant 93-G-060, and the Beckman Foundation and Institute for continuing support of the FTICR research facility. We also acknowledge Professor William A. Goddard, III, and the Beckman Institute Materials and Process Simulations Center for supporting our theoretical calculations. Francesco Faglioni gave especially helpful advice concerning the theoretical calculations in this work. This is Contribution 9166 from the Arthur Amos Noyes Laboratory of Chemical Physics.
Funding AgencyGrant Number
Federal Aviation Administration (FAA)93-G-060
Arnold and Mabel Beckman FoundationUNSPECIFIED
Caltech Beckman InstituteUNSPECIFIED
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Caltech Arthur Amos Noyes Laboratory of Chemical Physics9166
Issue or Number:6
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Official Citation:Chemical Ionization of TNT and RDX with Trimethylsilyl Cation. Kevin C. Crellin, M. Widmer, and J. L. Beauchamp. Analytical Chemistry 1997 69 (6), 1092-1101 DOI: 10.1021/ac961003q
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:81003
Deposited By: Tony Diaz
Deposited On:30 Aug 2017 23:34
Last Modified:15 Nov 2021 19:40

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