Reactions, Volume 3, Issue 1 (March 2022) – 17 articles

Titanium ferrite represents one of the most promising magnetic materials that exhibits optical absorption in both ultraviolet and visible spectral regions with a range of applications in photocatalysis, giant magnetoresistance, sensors, high-frequency modern power supplies, etc. Here in the present work, we report synthesizing titanium ferrite NPs via the co-precipitation method. As obtained ferrite nanopowders were characterized using XRD, UV-Visible absorption, Raman scattering, and variable sample magnetometer techniques. The crystalline size of NPs lies between 35 to 50 nm. The as-obtained nanopowder samples were calcined at 200, 500, 800 °C temperatures, and the resulting change in the optical, structural, and magnetic properties are investigated. The saturation magnetization of 500 °C calcined sample is higher than that calcined at 200 °C, but the magnetization value drastically becomes reduced for powder calcined at 800 °C temperature. The results of the present work can be used to understand the effects of annealing temperature on the structural and magnetic properties of other ferrite nanomaterials. Full article

Oligo(L-lactic acid) (OLLA) was synthesized by ring opening polymerization of L-lactides using stannous octoate (0.03 wt% of lactide). While this served as the initiator, L-lactic acids were the co-initiators at 140 °C for 10 h, wherein L-lactic acids were prepared by hydrolytic degradation of L-lactides at 100 °C for 1 h. The molecular weight or degree of polymerization was controlled with monomer/co-initiator ratio (mol/mol). α-cellulose and microcrystalline cellulose (MCC) were extracted from jute fiber by subsequent treatment with sodium chlorite (Na₂ClO₂), NaOH and H₂SO₄. Grafting of OLLA onto α-cellulose and MCC in toluene was carried out using para-toluene sulphonic acid as a catalyst and potassium persulphate (KPS) as an initiator at 130 °C under 380 mm (Hg) pressure for 3, 6, 9, 12, 15, and 18 h. New properties of α-cellulose and MCC were observed due to the successful grafting onto α-cellulose and MCC. Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscope (SEM) were conducted in order to confirm grafting of OLLA onto cellulose and MCC. The FTIR analysis results showed there are some new characteristic absorption peaks appeared (1728 to 1732 cm⁻¹) in the spectrum, which confirmed the grafting of OLLA onto α-cellulose and MCC was successful. SEM images of α-cellulose and MCC before and after grafting revealed significant changes in surface morphology. Grafting of MCC could be more effective for further application in comparison to α-cellulose. Full article

Thermogravimetric curves are measured in the nitrogen of wheat straw heated up to 773 K with rates between 5–20 K/min. A five-step (or component) parallel reaction scheme was developed for the interpretation of the weight loss characteristics, which makes use of the lumped volatile products based on the volatiles released by the pseudo-macrocomponents. The volumetric rates show the usual Arrhenius dependence on temperature and a linear dependence on the mass fraction of the lumped volatile products. The wheat straw devolatilization mechanism consists of a single step for pseud-ocellulose (activation energies of about 180 kJ/mol) and two steps for the pseudohemicellulose, also including extractives, (activation energies of about 101 and 136 kJ/mol) and pseudo-lignin (activation energies of 189 and 126 kJ/mol). For the first two pseudo-macrocomponents, the activation energies were lower than those obtained through a similar approach for beech wood, owing to the much higher content of alkalis acting as catalysts for the decomposition reactions. These occur at lower temperatures and show an enhanced overlap between the pseudo-components. Full article

The selective N-4 alkylation of cytosine plays a critical role in the synthesis of biologically active molecules. This work focuses on the development of practical reaction conditions toward a regioselective synthesis of N-4-alkyl cytosine derivatives. The sequence includes a direct and selective sulfonylation at the N-1 site of the cytosine, followed by the alkylation of the amino site using KHMDS in CH₂Cl₂/THF mixture, providing a fast and efficient approach consistent with pyrimidine-based drug design. Full article

Nucleophilic ring-opening reactions of cyclic oxonium derivatives of anionic boron hydrides are a convenient method of their modification which opens practically unlimited prospects for their incorporation into various macro- and biomolecules. This contribution provides an overview of the synthesis and reactivity of cyclic oxonium derivatives of nido-carborane as well as half-sandwich complexes based on it. Full article

The photocatalytic degradation of the valsartan (VLS) pharmaceutical using TiO₂ and g-C₃N₄ catalysts under simulated solar light is studied in this paper by high-resolution Orbitrap mass spectrometry. ^•OH radicals were the major oxidant species for the degradation of valsartan using TiO₂, while positive holes (h⁺), followed by a much lesser amount of ^•OH radicals, were the major species in the case of g-C₃N₄. Valsartan degradation followed first order kinetics by both catalysts with TiO₂ being the catalyst with the better photocatalytic efficiency. The transformation products (TPs) and their evolution profiles are identified and monitored, respectively, by means of LC-HRMS. Based on TPs identification, the degradation mechanisms are discussed. The major degradation pathways for g-C₃N₄ include decarboxylation and subsequent oxidation, hydroxylation, and cleavage of C–N bond, while for TiO₂ cyclization, TPs are abundant and the hydroxylation occurs in the first stage products. The study highlights the complex nature of TPs formed during such processes, the different mechanisms involved and the necessity for the identification of TPs for the assessment of the treatment and the tracking of such TPs in different environmental compartments. Full article

The E. coli 2-oxoglutarate dehydrogenase complex (OGDHc) is a multienzyme complex in the tricarboxylic acid cycle, consisting of multiple copies of three components, 2-oxoglutarate dehydrogenase (E1o), dihydrolipoamide succinyltransferase (E2o) and dihydrolipoamide dehydrogenase (E3), which catalyze the formation of succinyl-CoA and NADH (+H⁺) from 2-oxoglutarate. This review summarizes applications of the site saturation mutagenesis (SSM) to engineer E. coli OGDHc with mechanistic and chemoenzymatic synthetic goals. First, E1o was engineered by creating SSM libraries at positions His260 and His298.Variants were identified that: (a) lead to acceptance of substrate analogues lacking the 5-carboxyl group and (b) performed carboligation reactions producing acetoin-like compounds with good enantioselectivity. Engineering the E2o catalytic (core) domain enabled (a) assignment of roles for pivotal residues involved in catalysis, (b) re-construction of the substrate-binding pocket to accept substrates other than succinyllysyldihydrolipoamide and (c) elucidation of the mechanism of trans-thioesterification to involve stabilization of a tetrahedral oxyanionic intermediate with hydrogen bonds by His375 and Asp374, rather than general acid–base catalysis which has been misunderstood for decades. The E. coli OGDHc is the first example of a 2-oxo acid dehydrogenase complex which was evolved to a 2-oxo aliphatic acid dehydrogenase complex by engineering two consecutive E1o and E2o components. Full article

Bio-oil, although rich in chemical species, is primarily used as fuel oil, due to its greater calorific power when compared to the biomass from which it is made. The incomplete understanding of how to explore its chemical potential as a source of value-added chemicals and, therefore, a supply of intermediary chemical species is due to the diverse composition of bio-oil. Being biomass-based, making it subject to composition changes, bio-oil is obtained via different processes, the two most common being fast pyrolysis and hydrothermal liquefaction. Different methods result in different bio-oil compositions even from the same original biomass. Understanding which biomass source and process results in a particular chemical makeup is of interest to those concerned with the refinement or direct application in chemical reactions of bio-oil. This paper presents a summary of published bio-oil production methods, origin biomass, and the resulting composition. Full article

This article describes thermal input/concentration output systems processed by chemical reactions. Various sophisticated thermal inputs can be converted into concentration outputs through the double-helix formation of helicene oligomers exhibiting thermal hysteresis. The inputs include high or low temperature, cooling or heating state, slow or fast cooling state, heating state, and cooling history. The chemical basis for the properties of the chemical reactions includes the reversibility out of chemical equilibrium, sigmoidal relationship and kinetics, bistability involving metastable states, positive feedback by self-catalytic chemical reactions, competitive chemical reactions, and fine tunability for parallel processing. The interfacing of concentration outputs in other systems is considered, and biological cells are considered to have been utilizing such input/output systems processed by chemical reactions. Full article

1,3-Dienes are vital building blocks in organic synthesis. They underpin many fundamental synthetic transformations and are present in numerous natural products and drug candidate molecules. The rearrangement of an alkylallene to a 1,3-diene is an atom efficient, redox neutral, transformation that provides a straightforward synthetic route to functionalized 1,3-dienes. Herein, we provide an account of this transformation using allenes that are not predisposed by the presence of heteroatoms or electron-withdrawing groups directly attached to the allene. Early reports of this skeletal rearrangement are acid-mediated approaches, with limited substrate scope, but they provide valuable mechanistic insights. More recent transition metal-mediated approaches that exhibit improved substrate scope are described, together with isolated examples that have utilized this rearrangement. Full article

Synthetic access to poly(indazolyl)methanes has limited their study despite their structural similarity to the highly investigated chelating poly(pyrazolyl)methanes and their potentially important indazole moiety. Herein is presented a high yielding, one-pot synthesis for the 3d-metal catalyzed formation of bis(1H-indazol-1-yl)methane from 1H-indazole utilizing dimethylsulfoxide as the methylene source. Complete characterization of bis(1H-indazol-1-yl)methane is given with ¹H and ¹³C NMR, UV/Vis, FTIR, high resolution mass spectrometry and for the first time, single crystal X-ray diffraction. This simple, inexpensive pathway to yield exclusively bis(1H-indazol-1-yl)methane provides synthetic access to further investigate the coordination and potential applications of the family of bis(indazolyl)methanes. Full article

In this work, a highly selective and active gold-based catalyst for the oxidation of high concentrated monoethylene glycol (MEG) in aqueous solution (3 M, 20 wt%) is described. High glycolic acid (GA) selectivity was achieved under mild reaction conditions. The optimization of the catalyst composition and of the reaction conditions for the oxidation of MEG in semi-batch mode under alkaline conditions led to a GA yield of >80% with a GA selectivity of about 90% in short reaction time. The bimetallic catalyst 0.1 wt% AuPt (9:1)/CeO₂ showed very high activity (>2000 mmol_MEG/g_metalmin) in the oxidation of MEG and, contrary to other studies, an extremely high educt to metal mole ratio of >25,000 was used. Additionally, the gold–platinum catalyst showed a high GA selectivity over more than 10 runs. A very efficient and highly selective process for the GA production from MEG under industrial relevant reaction conditions was established. In order to obtain a GA solution with high purity for the subsequent polymerization, the received reaction solution containing sodium glycolate, unreacted MEG and sodium oxalate is purified by a novel down-stream process via electrodialysis. The overall GA yield of the process exceeds 90% as unreacted MEG can be recycled. Full article

Three different types of biomass sourced from forestry waste (eucalyptus residues), agricultural waste (wheat straw), and energy crop (miscanthus) were used as starting materials to produce hemicellulosic sugars, furans (furfural and hydroxymethylfurfural), and oligosaccharides. A two-step hybrid process was implemented; biomass was first autohydrolysed without any additive to extract hemicelluloses and dissolve it in water. Then, the hydrolysate was treated with a solid acid catalyst, TiO₂-WO_x, in order to achieve hydrolysis and produce monomeric sugars and furans. This article investigates the role of the biomass type, autohydrolysis experimental conditions, polymerisation degree and composition of hemicelluloses on the performance of the process coupling autohydrolysis and catalytic hydrolysis. The highest global yields of both oligosaccharides and monomeric sugars were obtained from Eucalyptus (37% and 18%, respectively). Full article

The construction of well-defined polyurethane dendrimers is challenging due to the high reactivity of externally added or in situ formed isocyanates leading to the formation of side products. With a primary focus of dendrimer research being the interaction of the periphery and the core, we report the synthesis of a common polyurethane dendron, which allows for the late-stage variation of both the periphery and the core. The periphery can be varied simply by installing a clickable unit in the dendron and then attaching to the core and vice-versa. Thus, a common dendron allows for varying periphery and core in the final two steps. To accomplish this, a protecting group-free, one-pot multicomponent Curtius reaction was utilized to afford a robust and versatile AB₂ type polyurethane dendron employing commercially available simple molecules: 5-hydroxyisophthalic acid, 11-bromoundecanol, and 4-penten-1-ol. Subsequent late-stage modifications of either dendrons or dendrimers via a thiol-ene click reaction gave surface-functionalized alternating aromatic-aliphatic polyurethane homodendrimers to generation-three (G3). The dendrons and the dendrimers were characterized by NMR, mass spectrometry, and FT-IR analysis. A bifunctional AB₂ type dendritic monomer demonstrated this approach’s versatility that can either undergo a thiol-ene click or attachment to the core. This approach enables the incorporation of functionalities at the periphery and the core that may not withstand the dendrimer growth for the synthesis of polyurethane dendrimers and other dendritic macromolecules. Full article

Despite numerous works devoted to the cellulose hydrogenolysis process, only some of them describe reaction kinetics. This is explained by the complexity of the process and the simultaneous behavior of different reactions. In this work, we present the results of the kinetic study of glucose hydrogenolysis into ethylene- and propylene glycols in the presence of Ru@Fe₃O₄/HPS catalyst as a part of the process of catalytic conversion of cellulose into glycols. The structure of the Ru-containing magnetically separable Ru@Fe₃O₄/HPS catalysts supported on the polymeric matrix of hypercrosslinked polystyrene was studied to propose the reaction scheme. As a result of this study, a formal description of the glucose hydrogenolysis process into glycols was performed. Based on the data obtained, the mathematical model of the glucose hydrogenolysis kinetics in the presence of Ru@Fe₃O₄/HPS was developed and the parameter estimation was carried out. The synthesized catalyst was found to be characterized by the enhanced magnetic properties and higher catalytic activity in comparison with previously developed catalytic systems (i.e., on the base of SiO₂). The summarized selectivity towards the glycols formation was found to be ca. 42% at 100% of the cellulose conversion in the presence of Ru@Fe₃O₄/HPS. Full article