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Date of Award

2005

Document Type

Dissertation - Pacific Access Restricted

Degree Name

Doctor of Philosophy (Ph.D.)

Department

Chemistry

First Advisor

Patrick Jones

First Committee Member

Elizabeth Day

Second Committee Member

Hugh Gregg

Third Committee Member

Andreas Franz

Fourth Committee Member

Jianhua Ren

Fifth Committee Member

David Sparkman

Abstract

PETN is characterized by its sensitivity to environmental conditions. However, anhydrous low-temperature decomposition is poorly understood. This research undertook the search for the decomposition products of naturally aged PETN. This study did not detect any decomposition products. The methods tried were NMR, HPLC, mass spectrometry, and HPLC. PETN's behavior was sensitive to mass spectral conditions and resulted in adduct formation and artifactual decomposition. Artifacts could be sources of misinterpretation for true decomposition. Such behaviors included PETN's autonitration and nitrate's clinging to instrument surfaces. Additionally, PETN seemed able to autooxidize which produced an [M] − ion and [M+H] − ion that obscured isotopic information. Conditions that enhanced the abundance of the [M−H] − ion also increased PETN artifactual decomposition. Because an ion at m/z 330 could represent PETRIN, it was studied and candidated to be an artifact. This PETRIN-acetate isobar was formed from PETN in the presence of acetate. An illusion that a new mass at m/z 330 materialized could be due to spray chamber temperatures. The ion stayed relatively constant throughout a temperature increase while the abundance for other PETN ions decreased. This created an illusion of increasing abundance when the mass spectrum was displayed in normalized mode. An HPLC gradient of acetonitrile/water with addition of 3% NH 4 OH and 0.1 M ammonium acetate in methanol produced chromatographic peaks. However, these species were artifacts formed in the presence of hydroxide ion. Hydroxide accelerated the disappearance of the ion at m/z 315, but not the ion at m/z 378. A second HPLC system used an acetonitrile/water gradient with added 3.3 M ammonium acetate in methanol. However, no difference between PETN and naturally aged PETN chromatograms was evident. In an additional experiment, with the HPLC effluent collected in aliquots and analyzed separately, no condensed phase decomposition product was observed. Because the NMR, HPLC and mass spectrometry experiments did not detect condensed phase decomposition products, the decomposition products might be gas(es). In support, the explosives HMX and RDX are known to decompose in gas phase reactions. It is reasonable that naturally aged PETN proceeds through the same mechanism. The findings of this dissertation supported this viewpoint.

Pages

228

ISBN

0542018063 , 9780542018060

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