Role of Hydroxyl Radical in Degradation of NTO: DFT Study

Abstract

Hydroxyl radicals are important reactive oxygen species produced in the aquatic environment under sunlight irradiation. Many organic pollutants may be decomposed as they encounter hydroxyl radicals, due to their high oxidative ability. NTO (5-nitro-1,2,4-triazol-3one), an energetic material used in military applications, may be released to the environment and dissolved in surface water and groundwater due to its good water solubility. A detailed investigation of the possible mechanism for NTO decomposition in water induced by hydroxyl radical as one of the pathways for NTO environmental degradation was performed by computational study at the PCM/M06-2X/6-311+ +G(d,p) level. Decomposition of NTO was found to be a multistep process that may begin with an addition of hydroxyl radical to the carbon atom of C�N double bond and consequent release of a nitrite radical. The formed intermediate undergoes a series of chemical transformations that include the attachments of hydroxyl radical to carbon atoms, the transfer of hydrogen to hydroxyl radical, isomerization, and bond cleavage, leading to low-weight inorganic compounds, such as ammonia, nitrogen gas, nitrous acid, nitric acid, and carbon(IV) oxide. The anionic form of NTO is more reactive toward interaction with the hydroxyl radical as compared with its neutral form. Calculated activation energies and high exergonicity of the studied process support the significant contribution of the hydroxyl radical to NTO mineralization in environment.

5-Amino-1,2,4-triazol-3-one Degradation by Indirect Photolysis: A Density Functional Theory Study

“…The predicted products of the multistep process of NTO photolysis were carbon(IV) oxide, carbon(II) oxide, nitrous acid, nitric oxide, hydrazine, ammonia, and nitrogen gas. We also modeled decomposition of NTO induced by reactive oxygen species (ROS) such as the hydroxyl radical, hydroperoxyl radical, superoxide, and singlet oxygen, which are produced in the aqueous solution under sunlight irradiation. − Our results revealed that ROS can cause mineralization of NTO, leading to products of NTO degradation such as nitrous acid, nitric acid, ammonia, nitrogen gas, and carbon(IV) oxide.…”

“…NTO undergoes different biotic and abiotic transformations in the environment. The variety of possible pathways for decomposition of NTO makes its study considerably interesting for experimental and computational chemistry. − NTO undergoes photodegradation upon exposure to UV radiation. The identified aqueous products of NTO phototransformation were nitrite, nitrate, ammonium, and 5-hydroxy-1,2,4-triazol-3-one. , Photolysis represents potentially significant degradation pathway for NTO in the environment, and understanding of the mechanism of photochemical degradation of NTO is necessary in order to predict and control its environmental fate and persistence.…”