Access Type

Open Access Dissertation

Date of Award

January 2016

Degree Type

Dissertation

Degree Name

Ph.D.

Department

Chemistry

First Advisor

Charles H. Winter

Abstract

One main aspect of high energy density material (HEDM) design is to obtain greener alternatives for HEDMs that produce toxic byproducts. Primary explosives lead azide, lead styphnate, and mercury fulminate contain heavy metals that cause heavy metal poisoning. Leaching of the widely used tertiary explosive NH4ClO4 into groundwater has resulted in human exposure to ClO4– ions, which cause disruptions of thyroid related metabolic pathways and even thyroid cancer. Many research efforts to find replacements have gained little success. Thus, there is a need for greener HEDMs. Peroxo-based oxygen-rich compounds are proposed as a potential new class of greener HEDMs due to the evolution of CO2 and/or CO, H2O, and O2 as the main decomposition products. Currently, triacetone triperoxide (TATP), diacetone diperoxide (DADP), hexamethylene triperoxide diamine (HMTD), and methyl ethyl ketone peroxide (MEKP) are the only well-studied highly energetic peroxides. However, due to their high impact and friction sensitivities, low thermal stabilities, and low detonation velocities they have not found any civil or military HEDM applications.

In this dissertation research, we have synthesized and fully characterized four categories of peroxo-based compounds: tert-butyl peroxides, tert-butyl peroxy esters, hydroperoxides, and peroxy acids to perform a systematic study of their sensitivities and the energetic properties for potential use as greener HEDMs.

tert-Butyl peroxides were not sensitive to impact, friction, or electrostatic spark. Hence, tert-butyl peroxides can be described as fairly safe peroxo-based compounds to handle. tert-Butyl peroxy esters were all surprisingly energetic (4896–6003 m/s), despite the low oxygen and nitrogen contents. Aromatic tert-butyl peroxy esters were much lower in impact and friction sensitivities with respect to the known peroxo-based explosives. These are among the first low sensitivity peroxo-based compounds that can be categorized as secondary HEDMs.

Oxygen-rich (0.80–1.00) geminal hydroperoxides have detonation velocities in the range of 6150–7130 m/s. These impressive detonation velocities are greater than the detonation velocities of the known peroxo-based explosives. The highest detonation velocity (7130 m/s) was obtained for 1,4-bis(dihydroperoxymethyl)benzene, which has the highest crystalline density (1.648 g/cm3). This detonation velocity is greater than the secondary explosive 2,4,6-trinitrotoluene (TNT). The sensitivities of these oxygen-rich geminal hydroperoxides are lower than the known peroxo-based explosives due to the O–H•••O hydrogen bonds and O•••O contacts, which stabilize the weak O–O bonds in the crystalline lattice. They could be useful as primary HEDMs.

Dihydroperoxy dioxane and dioxolanes have impressive detonation velocities in the range of 6350–6694 m/s. However, their extremely high sensitivities render them unsafe for HEDM applications. Interestingly, hydroperoxy dioxanol and dioxolanols also have high detonation velocities in the range of 6100–6461 m/s even with the lower oxygen contents. The hydroperoxy compounds with one less O–O bond were much less sensitive than the dihydroperoxy compounds. These hydroperoxy compounds could be useful as primary HEDMs. We observed that the ring strain was useful in increasing the detonation velocities, since it led to compounds with higher crystalline densities. However, increasing the steric strain using bulky groups led to lower crystalline densities and lower detonation velocities. Higher steric strain not only resulted in higher sensitivities but also lower thermal stabilities.

Peroxy acids have high detonation velocities in the range of 5262–7885 m/s. The detonation velocity of 3,5-dinitrobenzoperoxoic acid (7217 m/s) was the highest detonation velocity obtained for the peroxo-based compounds synthesized in our study, which is greater than the detonation velocity of TNT. The detonation velocity of 2,4,6-trinitrobenzoperoxoic acid (7885 m/s) is close to the detonation velocity of the secondary high explosive 1,3,5-trinitroperhydro-1,3,5-triazine (RDX). Peroxy acids have surprisingly low impact and friction sensitivities that are well below the known peroxo-based explosives TATP, DADP, HMTD, and MEKP. Based on the crystal structure of 3,5-dinitrobenzoperoxoic acid, the low sensitivities can be attributed to the stabilization of the weak O–O bonds in the crystalline lattice by O–H•••O hydrogen bonds and O•••O short contacts. These are the first peroxo-based oxygen-rich compounds that can be useful as secondary HEDMs. The ease of synthesis in high yields with minimum synthetic manipulations, storability, and high thermal stabilities are all advantageous properties of peroxy acids for their use as HEDMs.

Through this work, we have gained a wealth of fundamental information about the structures and energetic materials properties of a large family of peroxo-based compounds. Solid state intermolecular interactions were useful to understand the impact and friction sensitivities. The safe peroxy O:C ratio was found to be approximately 1.00. However, the oxygen contents could be further increased with more stable nitro and hydroxy groups. Highly attractive low sensitivity peroxo-based compounds were obtained with impressive detonation performances for potential use as greener primary and secondary HEDMs.

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