Chemistry of Organic Nitrates: Thermal Oxidative and Catalytic Chemistry of Organic Nitrates

Abstract

Our previous research showed that the rates for unimolecular thermal fragmentation of the O-N bond of organic nitrates are the same in air as they are under a nitrogen atmosphere. This is contrary to what literature studies have reported. When the rate of reaction was followed by infrared (IR) spectroscopy, as in previous literature studies, the IR absorption of the unsaturated carbonyls generated during the reaction complicated the IR analysis and the rates deceptively appeared to slow in air. The current study shows that unsaturated carbonyls can also be formed under a nitrogen atmosphere when hydroperoxide is added. Hydroperoxides created naturally most likely give rise to the unsaturated carbonyl compounds when the reaction is carried out in air. Evidence suggests that the products of organic nitrate thermal chemistry accelerate the decomposition of the model hydroperoxide. The details of this chemistry are critical for controlling the oxidation of hydrocarbons. The reaction of organic nitrates with various catalytic compounds has also been studied. The catalysts fall into three categories: (1) no effect on the rate of loss of organic nitrate or the type of products generated over the thermal base case, (2) accelerate the loss of organic nitrate, but the products remain the same as the thermal base case, and (3) accelerate the loss of organic nitrate and generate different products than the thermal base case. Catalytic amounts (3 mol %) of copper(II) oleate and iron(III) acetyl acetonate each increased the rate of loss of organic nitrates at 170 °C under N 2 by a factor of 1.5 and 2, respectively. The reactions remained first order (or pseudo-first order). Changes in product distribution, in some cases, indicate that the mechanism may be non-radical. Copper and iron compounds convert organic nitrates to stable products before they can cleave thermally and form radicals or react directly with other molecules. Hydroperoxides react with some of the same catalysts, but they also react with compounds that have no effect on organic nitrates.

Synthesis of bis‐Isoxazole‐bis‐Ethylene Dinitrate and bis‐Isoxazole‐tetra‐Ethylene Tetranitrate: Potential Energetic Plasticizers

“…A common decomposition pathway of nitroxymethyl groups under heat is the scission of the side chain via the loss of formaldehyde [21]. In a compound with a nitroxymethyl moiety, the nitrate ester functionality can be lost under thermal stress through a radical pathway, resulting in formation of an aldehyde or carboxylic acid group [22]. There is additional driving force for this transformation if the nitroxymethyl is attached to an aromatic ring, as the carbonyl functionality will be in conjugation.…”