Scott A. Shackelford

Comparative mechanistic thermochemical decomposition analyses of liquid hexahydro-1,3,5-trinitro-13,5-triazine (RDX) using the kinetic deuterium isotope effect approach

Abstract The condensed phase kinetic deuterium isotope effect (KDIE) approach is applied to the thermochemical decomposition of liquid RDX and RDX- d 6 using two dissimilar thermal analysis techniques. Comparative KDIE results from isothermal differential scanning calorimetry (IDSC) and from direct RDX concentration depletion measurements by quenched UV spectrometric analysis confirm the proposed proportionality between IDSC heat evolution rates and the RDX concentration depletion rate. Additionally, these KDIE data verify the proposed rate-controlling mechanistic step previously reported from an isothermal thermogravimetric investigation of liquid RDX determined from weight loss rates. Observed mechanistic and kinetic differences between the cyclic six-membered RDX decomposition and its eight-membered HMX homologue are outlined.

Mechanistic Investigations of Condensed Phase Energetic Material Decomposition Processes Using the Kinetic Deuterium Isotope Effect

The condensed phase kinetic deuterium isotope effect (KDIE) approach directly reveals the rate-controlling mechanistic step that ultimately determines the rate at which energy is released by an energetic materia’s thermochemical decomposition process. This paper reviews the KDIE concept and discusses previous condensed phase KDIE mechanistic investigations conducted during the thermochemical decomposition process of various nitroaromatic (TNT, HNBB, TATB) and nitramine (HMX, RDX) compounds using isothermal DSC and TGA analyses. Isothermal DSC evaluation methods used for obtaining an energetic compound’s KDIE and in determining its rate-controlling step are outlined, and the possible dependence of the rate-limiting step on an energetic compound’s physical state during the thermochemical decomposition process is considered.

Xenon difluoride fluorination. IV. Photochemically initiated xenon difluoride fluorination of norbornene

Abstract Norbornene was selectively fluorinated with xenon difluoride by photochemical means. Unrearranged 2,3-difluoronorbornane isomers and acetonitrile solvent adducts were the exclusive products. This represents a novel example of controlled XeF 2 radical fluorination by light initiation.

Electrophilic tetraalkylammonium nitrate nitration. I. Convenient new anhydrous nitronium triflate synthesis and in-situ heterocyclic N-nitration

Reaction of tetra-n-butylammonium nitrate and triflic anhydride, CF3SO2OSO2CF3 (Tf2O), in dichloromethane (CH2Cl2) solvent at 0 degrees C, produces anhydrous nitronium nitrate, NO2OSO2CF3 (NO2OTf). Subsequent introduction of various heterocycles and their N-acetylated analogs yield N-nitrated products in 20–76% yield with an overall one-pot procedure.

MECHANISTIC RELATIONSHIPS OF THE DECOMPOSITION PROCESS TO COMBUSTION AND EXPLOSION EVENTS FROM KINETIC DEUTERIUM ISOTOPE EFFECT INVESTIGATIONS

The condensed phase kinetic deuterium isotope effect (KDIE) approach directly determines the overall rate-controlling mechanistic step of an energetic material’s complex thermochemical decomposition process. This second paper discusses extending the KDIE approach into progressively more drastic high temperature/pressure/rate regimes encountered with pyrolytic decomposition/deflagration, combustion, thermal explosion, and detonation incidents in order to determine the rate-controlling step of each. This rate-controlling step provides a common basis for comparing the mechanistic similarities or differences among these high energy incidents; and possible relationships between the thermochemical decomposition process and higher order combustion or explosion incidents are described for HMX, RDX, TATB, and TNT. The KDIE determined rate-controlling step between a pure nitramine compound and a formulated energetic material also is compared.

Direct polynitroaliphatic alcohol addition to alkenes. 3. Synthesis, structure and intramolecular electron impact stability of the uniquely structured 2,4-dimethyl-7,7-dinitro-1,3,5-trioxacyclooctane

Mercury(I) sulfate catalyzed addition between the difunctional 2,2-dinitropropane-1,3-diol (ADIOL) and the divinyl ether (DVE) diene reactants produces either an apparent acyclic acetal oligomer, or the unexpected eight-membered 2,4-dimethyl-7,7-dinitro-1,3,5-trioxacyclooctane. Proton nmr and deuterium labeling of this heterocyclic compound reveals it is comprised of both meso and dl diastereomers caused from its two chiral carbon atoms. Because this heterocycle incorporates both gem-2,2-dinitroalkyl and cyclic trioxane acetal structural fragments into one hybrid saturated ring structure, a novel intramolecular electron impact stability comparison can be made between the structural features representative of the normally unrelated geminal polynitroalkane and cyclic polyoxane compound classes which determine the fragmentation pathway of the subject heterocycle

Benchtop synthesis and characterization of air-stable titanocene(IV) complexes from phosphorous- and sulfur-based amino acid analogs

Four new air-stable titanocene(IV) salt complexes were synthesized by reacting titanocene dichloride with phosphorous- and sulfur-based β-amino acid analogs in standard chemical glassware open to atmospheric conditions. Each new titanocene(IV) complex contained two identical ligands with a terminal ammonium chloride group and either the phosphorous- or sulfur-based ester group bonded directly to the central titanium atom. Each complex was characterized by 1H, 13C, and 31P NMR, IR, UV, and MS analyses. Initial data revealed the titanocene(IV) complexes with sulfonate or sulfate amino ester ligands to be far more stable to hydrolysis than the analogous phosphonate or phosphate amino ester complexes.

ADDITION REACTIONS OF ALKENES WITH ELECTRONEGATIVELY SUBSTITUTED ALCOHOLS IN THE PRESENCE OF XENON DIFLUORIDE

The electrophilic reactivity of proposed alkoxyxenon fluoride (ROXeF) intermediates based on electronegatively substituted (polyfluorinated and polynitroaliphatic) alcohols has been characterized with model alkenes norbornene, 2-methylpent-1-ene and hex-1-ene. The alkoxyxenon fluorides can react as positive oxygen electrophiles—initially incorporating alkoxy substituents—or as apparent fluorine electrophiles—resulting in initial fluorine incorporation—depending on conditions. Efficient simple addition of poorly nucleophilic alcohols to norbornene was observed in certain systems. Selectivity between the various reaction paths (simple fluorination, alkoxyfluorination or alcohol addition) was observed to be a sensitive function of various reaction conditions, especially solvent, temperature and catalyst.