Synthesis of High Molecular Weight Stereo-Di-Block Copolymers Driven by a Co-Initiator Free Catalyst

Stereo-diblock copolymers of high molecular weight polylactide (PLA) were synthetized by the one pot-sequential addition method assisted by a heteroscorpionate catalyst without the need of a co-initiator. The alkyl zinc organometallic heteroscorpionate derivative (Zn(Et)(κ3-bpzteH)] (bpzteH = 2,2-bis(3,5-dimethylpyrazol-1-yl)-1-para-tolylethoxide) proved to assist in the mechanism of reaction following a coordination-insertion process. Kinetic studies along with the linear correlation between monomer and number average molecular weight (Mn) conversion, and the narrow polydispersities supported the truly living polymerization character of the initiator, whereas matrix-assisted laser desorption/Ionization-time of flight (MALDI-TOF) studies showed a very low order of transesterification. The high stereo-control attained for the afforded high molecular weight derivatives was revealed by homonuclear decoupled 1H NMR spectra and polarimetry measurements. The nanostructure of the PLA derivatives was studied by both wide-angle X-ray scattering (WAXS) and differential scanning calorimetry (DSC) and the stereocomplex phase of the PLA stereo-diblock copolymers was successfully identified.

Synthesis and Characterization of New Boron Compounds Using Reaction of Diazonium Tetraphenylborate with Enaminoamides

A family of oxazaborines, diazaborinones, triazaborines, and triazaborinones was prepared by reaction of polarized ethylenes, such as β-enaminoamides, with 4-methylbenzenediazonium tetraphenylborates. The reaction conditions (stirring in CH2Cl2 at room temperature (Method A) or stirring with CH3COONa in CH2Cl2 at room temperature (Method B) or refluxing in the CH2Cl2/toluene mixture (Method C)) controlled the formation and relative content of these compounds in the reaction mixtures from one to three products. Substituted oxazaborines gradually rearranged into diazaborinones at 250 °C. The prepared compounds were characterized by 1H NMR, 13C NMR, IR, and UV–Vis spectroscopy, HRMS, or microanalysis. The structure of individual compounds was confirmed by 11B NMR, 15N NMR, 1D NOESY, and X-ray analysis. The mechanism of reaction of enaminoamides with 4-methylbenzenediazonium tetraphenylborate was proposed.

effect of 1Me-3H additive on the explosive force nanothermite systems SnO2/Al and WO3/Al

Нанотермиты рассматриваются как перспективные энергонасыщенные материалы для создания пиротехнических изделий широкого спектра, ввиду их способности горения в тонких слоях, микрограммовых навесках. Однако из-за высокой чувствительности нанотермитов к электрической искре и трению, сильно осложняется их практическое использование, в связи с чем актуален поиск добавок, снижающих чувствительность, но сохраняющих приемлемые параметры взрывчатых характеристик нанотермитных композиций. В качестве таковых добавок целесообразно использовать высокоэнтальпийные вещества, отличающиеся низкой чувствительностью. Одним из таких веществ является 1-метил-3-нитро-1,2,4-триазол (1Ме-3Н). В работе представлены результаты исследования силы взрыва (F) нанотермитных систем на основе оксида олова и алюминия SnO2/Al, оксида вольфрам и алюминия WO3/Al в зависимости от содержания 1Ме-3Н. Исследован ряд составов разной рецептурной компоновки (I и II): в компоновке I – соотношение компонентов в нанотермитной композиции соответствовало максимальной расчетной теплоте взрыва (Q) при заданном содержании 1Ме-3Н; II – соотношение компонентов базовой нанотермитной пары остается неизменным в тройных смесях. В системе SnO2/Al/1Ме-3Н выявлен экстремальный характер зависимости силы взрыва F от концентрации 1Ме-3Н, при этом максимальные значения F наблюдаются при содержании добавки 10 % для обоих рецептурных компоновок: I – F = 163 %; II – F = 160 %. Для системы WO3/Al/1Ме-3Н обоих рассмотренных рецептурных компоновок наблюдается монотонное снижение силы взрыва с ростом содержания1Ме-3Н: при содержании добавки 15 % композиция теряет взрывчатые свойства (F=0 %). Нанотермитная система SnO2/Al/1Ме-3Н, как и ранее изученные CuO/Al/1Ме-3Н, Bi2O3/Al/1Ме-3Н, MoO3/Al/Ме-3Н проявляет экстремальный характер зависимости силы взрыва F от содержания 1Ме-3Н, подтверждая ранее принятые положения о механизме реакционного взаимодействия в нанотермитных композициях с органическими добавками, тогда как для композиции WO3/Al/1Ме-3Н, по-видимому, присущ отличный от принятого механизм горения, требующий дополнительных исследований. Nanothermites are considered as promising energy-saturated materials for the creation of pyrotechnic products of a wide range, due to their ability to burn in thin layers, microgram quantities. However, due to the high sensitivity of nanothermites to electric spark and friction, their use is very difficult, and therefore the search for additives that reduce sensitivity, but retain acceptable parameters of explosive characteristics of nanothermite compositions is relevant. As such additives, it is advisable to highly use enthalpy substances characterized by low sensitivity. One of these substances is 1-methyl-3-nitro-1,2,4-triazole (1Me-3H). The paper presents the results of a study of the explosion force (F) of nanothermite systems based on tin oxide and aluminum SnO2/Al, tungsten oxide and aluminum WO3/Al depending on the content of 1Me-3H. Several compositions of different prescription configuration (I and II) were studied: in the configuration, I - the ratio of components in the nanothermite composition corresponded to the maximum calculated heat of explosion (Q) at a given content of 1Me-3H; II - the ratio of the components of the base nanothermite pair remains unchanged in triple mixtures. In the SnO2/Al/1Me-3H system, the extreme nature of the dependence of the explosion force F on the concentration of 1Me-3H was revealed, while the maximum values of F were observed at an additive content of 10% for both prescription configuration: I - F = 163%; II - F = 160%. For the WO3/Al/1Me-3H system of both considered compounding arrangements, a monotonous decrease in the explosion force with an increase in the content is observed 1Me-3H: with an additive content of 15%, the composition loses explosive properties (F = 0%). The nanothermite system SnO2/Al/1Me-3H, as well as the previously studied CuO/Al/1Me-3H, Bi2O3/Al/1Me-3H, MoO3/Al/Me-3H, exhibits an extreme dependence of the explosion force F on the content of 1Me-3H, confirming the previously accepted provisions on the mechanism of reaction interaction in nanothermite compositions with organic additives, whereas the composition WO3/Al/1ME-3H, apparently, has a different combustion mechanism from the accepted one, requiring additional research.

Phosphorylation of Cellulose in the Presence of Urea. Mechanism of Reaction and Reagent Impact.

A mechanism of cellulose phosphorylation in presence of urea is proposed. This model is correlated with the thermal stability of phosphorylating reactive mixture and the yield of phosphorylation for two different reagents: phosphoric acid and lauryl phosphate monoester. Three main successive reactions are involved in the formation of cellulose phosphate: (1) generation of ammonia by urea decomposition, (2) formation of phosphoramidate as intermediate reactive due to the reaction of ammonia with phosphate species, and (3) grafting the phosphate moiety to substrate due to the transfer of phosphate from phosphoramidate to cellulose. The proposed in vitro mechanism is supported by similar phosphorylation processes observed in some biochemical reactions. The limiting factor in the phosphorylation of cellulose is the formation of phosphoramidate intermediate.

QUANTUM-CHEMICAL STUDY OF THE MECHANISM OF REACTION OF DIFORMYLHYDRAZINE WITH p-AMINOPHENOL

Based on the results of a quantum chemical study within the framework of the elec tron density functional theory by the B3LYP/6-311++G(d, p) method, a theoretical mechanism for the reaction of diformylhydrazine with p-aminophenol is proposed

Mechanism of inhibition of SARS-CoV-2 Mpro by N3 peptidyl Michael acceptor explained by QM/MM simulations and design of new derivatives with tunable chemical reactivity

QM/MM simulations identify the mechanism of reaction of N3, a covalent peptidyl inhibitor of SARS-CoV-2 main protease. Modelling of two novel proposed compounds, B1 and B2, suggests that reversibility of covalent inhibition could be tailored.

Computational study on the reaction mechanism of Cp*Rh(III)-catalyzed cross-coupling reactions

The reaction mechanism of reaction reported by Onodera et al4 was studied in the M06L/Def2SVP level of theory. Two possible reaction products were characterized, named as product a and product b, where product a that was identified in the experimental study is due to a exergonic reaction and product b due to a endoergonic reaction.

QUANTUM-CHEMICAL STUDY OF THE MECHANISM OF REACTION OF BENZOELACETHYLENE WITH DITIO- AND DISELENOMALONAMIDES

A mechanism of the interaction of benzoylacetylene with dithio- and diselenomalonamides has been proposed on the basis of quantum-chemical calculations in the framework of the density functional theory using the B3LYP/6-311++G(d,p) basis set taking into account solvent effects (AcOH) within the polarizable continuum model, PCM, with inclusion of the HCl molecule in the calculated space. It is shown that the reaction involves two stages to afford heterocyclic compounds of the dithiine and diselenine type

RNA-Dependent RNA Polymerase From SARS-CoV-2. Mechanism Of Reaction And Inhibition By Remdesivir

We combine sequence analysis, molecular dynamics and hybrid quantum mechanics/molecular mechanics simulations to obtain the first description of the mechanism of reaction of SARS-CoV-2 RNA-dependent RNA polymerase (RdRp) and of the inhibition of the enzyme by Remdesivir. Despite its evolutionary youth, the enzyme is highly optimized to have good fidelity in nucleotide incorporation and a good catalytic efficiency. Our simulations strongly suggest that Remdesivir triphosphate (the active form of drug) is incorporated into the nascent RNA replacing ATP, leading to a duplex RNA which is structurally very similar to an unmodified one. We did not detect any reason to explain the inhibitory activity of Remdesivir at the active site. Displacement of the nascent Remdesivir-containing RNA duplex along the exit channel of the enzyme can occur without evident steric clashes which would justify delayed inhibition. However, after the incorporation of three more nucleotides we found a hydrated Serine which is placed in a perfect arrangement to react through a Pinner’s reaction with the nitrile group of Remdesivir. Kinetic barriers for crosslinking and polymerization are similar suggesting a competition between polymerization and inhibition. Analysis of SARS-CoV-2 mutational landscape and structural analysis of polymerases across different species support the proposed mechanism and suggest that virus has not explored yet resistance to Remdesivir inhibition.