Comparison of Oxidative Powers of DADP and TATP - A DFT Treatise

Diacetone diperoxide (DADP) and triacetone triperoxide (TATP) are very sensitive organic-peroxide type explosives which are easily synthesized. The present density functional treatment considers oxidative powers of DADP and TATP molecules based on comparison of their interactions with certain group II-metals at the level of B3LYP/6-311++G(d,p). Composite systems of DADP and TATP with Be, Mg and Ca have been considered. Although, in the case of beryllium composites, DADP and TATP and in the magnesium composite of DADP the organic component remains intact, Ca composites of DADP and TATP undergo ring rapture. Certain structural, electronic, quantum chemical and some spectral properties of the composites have been obtained and discussed.

Charged Forms of Diacetone Diperoxide - DFT Treatment

Diacetone diperoxide (DADP) is one of the sensitive and powerful organic peroxide explosives like its trimeric analogue TATP. Presently, some ionic forms of it have been investigated within the limitations of density functional theory at the level of UB3LYP/6-311++G(d,p). Various properties (including structural, electronic, spectral and quantum chemical) have been obtained and discussed. The studied mono and dianions having different multiplicity states have been found to be stable but monocation form decomposed.

Addition of divinyl benzene comonomer to glycidyl methacrylate grafting to cyclic natural rubber

The process of thermally grafting glycidyl methacrylate (GMA) on cyclic natural rubber (CNR) compared to the addition of an initiator of organic peroxide, dicumyl peroxide (DCP) and using cross-linker divinyl benzene (DVB) has been carried out by means of melt processing. The main aims of the modified GMA grafted to CNR was to increase the polarity of the polymer to be used as a compatibiliser agent in asphalt modification. The addition of DVB comonomer in the processing was to increase the amount of GMA implanted in cyclic rubber as measured by the degree of GMA grafting. The grafting method was carried out by melting polymer (melt processing) at high temperatures in the reactor internal mixer (Brabender model). The grafting reaction took place at a temperature of 160°C, 60 rpm rotor rotation for 10 minutes of mixing. To determine the GMA grafting reaction on cyclic rubber, characterization was carried out with Fourier Transformed Infra Red (FT-IR) while the degree of GMA grafting on natural rubber was determined by acid-base titration method in organic solvents. It was found that the GMA grafting process on cyclic natural rubber could easily occur in the melting phase at high temperatures and increase with the addition of dicumyl peroxide (DCP) peroxide. Although the addition of divinyl benzene (DVB) comonomer can increase the degree of grafting of GMA on CNR, the addition of comonomer can cause high cross-linking.

Urm1, not quite a ubiquitin-like modifier?

Ubiquitin related modifier 1 (Urm1) is a unique eukaryotic member of the ubiquitin-fold (UbF) protein family and conserved from yeast to humans. Urm1 is dual-functional, acting both as a sulfur carrier for thiolation of tRNA anticodons and as a protein modifier in a lysine-directed Ub-like conjugation also known as urmylation. Although Urm1 conjugation coincides with oxidative stress and targets proteins like 2-Cys peroxiredoxins from yeast (Ahp1) and fly (Prx5), it was unclear how urmylation proceeds molecularly and whether it is affected by the activity of these antioxidant enzymes. An in-depth study of Ahp1 urmylation in yeast from our laboratory (Brachmann et al., 2020) uncovered that promiscuous lysine target sites and specific redox requirements determine the Urm1 acceptor activity of the peroxiredoxin. The results clearly show that the dimer interface and the 2-Cys based redox-active centers of Ahp1 are affecting the Urm1 conjugation reaction. Together with in vivo assays demonstrating that high organic peroxide concentrations can prevent Ahp1 from being urmylated, Brachmann et al. provide insights into a potential link between Urm1 utilization and oxidant defense of cells. Here, we highlight these major findings and discuss wider implications with regards to an emerging link between Urm1 conjugation and redox biology. Moreover, from these studies we propose to redefine our perspective on Urm1 and the molecular nature of urmylation, a post-translational conjugation that may not be that ubiquitin-like after all.

Interaction of TATP with Some Group II Metals - A DFT Treatment

Triacetonetriperoxide (TATP) is a very sensitive organic peroxide type explosive which attracts the attention of terrorist groups due to its easy synthesis. The present density functional treatment considers the interaction of TATP molecule with certain group II metals at the level of B3LYP/6-311+G(d,p). Composite systems of TATP and Be, 2Be, Mg and Ca have been considered. Although, in the case of beryllium composites TATP molecule remains intact, in its Mg and Ca composites the rupture of the ring (even in 1:1 composite) occurs. Certain structural, electronic, quantum chemical and some spectral properties of the composites have been obtained and discussed.

OZONE FEATURES IN THE CONTEXT OF ADVANCING COVID-19 PANDEMIC

Coronavirus disease 2019 represents a serious challenge for modern society worldwide because of the considerable and unfavourable consequences of the pandemic in terms of human health, economics and social life. In the present survey, some essential peculiarities of ozone as an air pollutant and powerful oxidant under the conditions of the COVID-19 pandemic as reflected in the recent literature are described. The understanding of ozone chemistry during COVID-19 lockdown can improve ozone parameterization in models of chemical transport. Ozone peroxides such as ozonides, aldehydes, hydrogen peroxides, and organic peroxide serve as messengers to modulate the human immune system and improve blood rheology.

Catalytic Oxidations with Meta-Chloroperoxybenzoic Acid (m-CPBA) and Mono- and Polynuclear Complexes of Nickel: A Mechanistic Outlook

Selective catalytic functionalization of organic substrates using peroxides as terminal oxidants remains a challenge in modern chemistry. The high complexity of interactions between metal catalysts and organic peroxide compounds complicates the targeted construction of efficient catalytic systems. Among the members of the peroxide family, m-chloroperoxybenzoic acid (m-CPBA) exhibits quite complex behavior, where numerous reactive species could be formed upon reaction with a metal complex catalyst. Although m-CPBA finds plenty of applications in fine organic synthesis and catalysis, the factors that discriminate its decomposition routes under catalytic conditions are still poorly understood. The present review covers the advances in catalytic C–H oxidation and olefine epoxidation with m-CPBA catalyzed by mono- and polynuclear complexes of nickel, a cheap and abundant first-row transition metal. The reaction mechanisms are critically discussed, with special attention to the O–O bond splitting route. Selectivity parameters using recognized model hydrocarbon substrates are summarized and important factors that could improve further catalytic studies are outlined.