Espinosa Fuentes, Eduardo A.

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2009 - 200912010 - 20131
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    Experimental and Dft Studies of the mechanism of cetone-peroxide formation reaction using Raman and nuclear magnetic resonance spectroscopies
    (2009) Espinosa Fuentes, Eduardo A.; Hernández Rivera, Samuel P.; College of Arts and Sciences - Sciences; Román Velázquez, Félix R.; Mina Camilde, Nairmen; Department of Chemistry; Briano Peralta, Julio G.
    A mechanism for the reaction between acetone and hydrogen peroxide leading to the formation of the important homemade explosive Acetone Peroxide is postulated. The proposed mechanistic scheme is based on Raman and Nuclear Magnetic Resonance spectroscopies measurements and is also supported by ab-initio Density Functional Theory calculations using B3LYP 6-311g**d++ method. It was found that for the uncatalized reaction, the proposed mechanism of cyclic organic peroxides formation occurs in three steps: monomer formation, polymerization of the 2-hydroperoxipropan-2- ol monomer and cyclization. Calculated rate constants proved to be in agreement with theoretical calculations. The activation energy obtained confirms that the polymerization step is favored in comparison to other possible pathways. In fact, the activation energy is twofold lower than the acetone-monomer reaction and the peroxide-monomer reaction according to experimental and theoretical measurements, which was previously proposed.
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    Synthesis, formation mechanism and characterization of peroxide homemade explosives
    (2013) Espinosa Fuentes, Eduardo A.; Hernández Rivera, Samuel P.; College of Arts and Sciences - Sciences; Román Velázquez, Félix R.; Mina Camilde, Nairmen; Vega Olivencia, Carmen A.; Department of Chemistry; Almodovar Montanez, Jorge
    An important consideration in the area of homemade explosives, which are made from household products, is that it is difficult to control their production and use in terrorist activities. Therefore, security and defense agencies are very interested in getting a handle on this persistent problem. All these contributions can assist directly or indirectly to control the production and use of these explosives materials and improve and expand their spectroscopy based detection, which has been an active area of research. Specifically, knowing their formation mechanism helps to find substances that can inhibit the formation of these explosives. On the other hand, the mass fragmentation pattern is useful in the unequivocal identification in the different ports, among others applications. This scientific contribution describes a series of studies aimed to improving of homemade explosives (HME) synthesis, proposing of a mechanism for the uncatalyzed formation reaction of the most important HME: triacetone triperoxide, thermal characterization studies of HME, and other physical chemistry characterization studies including mass spectrometry, Raman spectroscopy and infrared spectroscopy. Specifically, it deals with: (1) Proposing of a viable mechanism for cyclic acetone-peroxide (CAP) formation reaction based entirely on qualitative and quantitative experimental measurements and supported by density functional theory theoretical modeling of the proposed intermediates and transition states. The experimental and theoretical results demonstrated that the proposed mechanism for the uncatalyzed reaction of CAP formation occurs in three steps: monomer formation, polymerization of the 2-hydroperoxipropan-2-ol monomer and cyclization. The temporal decays of the spectroscopic intensities of the tentatively assigned main vibrational bands are in complete agreement with the mechanism proposed. (2) A novel method to synthesize diacetone diperoxide (DADP) from acetone and hydrogen peroxide without the presence of a catalytic agent. Previously reported syntheses used toluene sulfonic and m-sulfonic acid as catalyst. DADP was prepared with a purity of 99.99%; the melting point range (128.5-134.5oC) consistently agreed with this value. The success of the procedure strictly depends on controlling the ratio between acetone and hydrogen peroxide as well as the temperature of the reaction mixture. (3) Determination of sublimation enthalpies of homemade cyclic acetone-peroxide explosives and homemade amino-peroxide explosives using thermogravimetric analysis and Fourier Transform infrared spectroscopy grazing angle probe measurements. The proposed method is direct because, it results from fitting the mass loss rate constants Ksub (T) vs. temperature without assuming values for associated constants. The enthalpy values obtained were comparable with previously reported values and values of the coefficients of determinations (R2 ) of the fittings obtained were all above 0.999+, which have high level of acceptance. (4) A simple method to isolate both D3 and C2-TATP conformers, which consists of multiple recrystallization steps using different solvent and heating to boiling. Spectroscopic and physical measurements such as: Raman spectra, X-ray diffraction and melting points showed that both clear and opaque crystals are different conformations of TATP. An experimental value of the transition energy between both conformers was also found using the Raman shifts. (5) Characterization of tetramethylene diperoxide dicarbamide (TMDD) compound was accomplished using DART-MS using ammonia vapor as gas dopant. The DART mass spectra of TMDD showed a strong ammonium adduct peak [M-NH4] + at 254 m/z and a more intense protonated molecular mass [M-H]+ at 237.084 m/z corroborating the identity of the sample analyzed. The DART-MS spectra of the TMDD isotopomers successfully corroborated the respective molecular tails.