Sulfur-centered radicals have a key role in a plethora of synthetic organic transformations, whose scope has been further expanded thanks to the possibility to generate such species under visible light photocatalytic conditions. The current literature overview focuses on those transformations involving isocyanides and sulfur-centered radicals with the aim to highlight the chemical space accessible, both in terms of complexity and diversity, and the mechanistic rational underpinning the current and future development of such chemical methodologies.
Monthly Archives: September 2023
UVA‐Light Promoted Catalyst‐Free Photochemical Aerobic Oxidation of Boronic Acids
The hydroxy group, and the phenol moiety in particular, is ubiquitous in several natural products, in organic synthesis and/or pharmaceutical industry. With the uprise of photoredox catalysis, many efforts worldwide focus on developing novel and sustainable protocols, providing an easy access to hydroxy-containing molecules. Boronic acids and boronic ester derivatives are considered valuable precursors for the synthesis of hydroxyl group derivatives. Herein, we report a novel, sustainable, light-driven protocol, where the impact of wavelength irradiation on boronic acid aerobic photooxidation was examined. In this work, UVA-light (370 nm) irradiation was found to promote the photocatalyst-free aerobic oxidation of boronic acids and boronic acid derivatives. Furthermore, a broad scope of substrates was tested and extensive mechanistic studies were performed, in order to probe the reaction mechanism.
Development and Validation of Multiple Linear Regression Models for Predicting Chronic Zinc Toxicity to Freshwater Microalgae
Abstract
Multiple linear regression (MLR) models were developed for predicting chronic zinc toxicity to a freshwater microalga, Chlorella sp., using three toxicity modifying factors (TMF): pH, hardness, and dissolved organic carbon (DOC). The interactive effects between pH and hardness, and pH and DOC were also included. Models were developed at three different effect concentration (EC) levels, including the EC10, EC20 and EC50 level. Models were independently validated using six different zinc-spiked Australian natural waters with a range of water chemistries. Stepwise regression found hardness to be an influential TMF in model scenarios and was retained in all final models, while pH, DOC and interactive terms had variable influence and were only retained in some models. Autovalidation and residual analysis of all models indicated that models generally predicted toxicity and there was little bias based on individual TMF. The MLR models, at all effect levels, performed poorly when predicting toxicity in the zinc-spiked natural waters during independent validation, with models consistently overpredicting toxicity. This overprediction may be from another unaccounted for TMF that may be present across all natural waters. Alternatively, this consistent overprediction questions the underlying assumption that models developed from synthetic laboratory test waters can be directly applied to natural water samples. Further research into the suitability of applying synthetic laboratory water-based models to a greater range of natural waters is need.
Aza‐Michael Addition in Explicit Solvent: A Relative Energy Gradient – Interacting Quantum Atoms Study
Aza-Michael additions are key reactions in organic synthesis. We investigate, from a theoretical and computational point of view, several examples ranging from weak to strong electrophiles in dimethylsulfoxide treated as explicit solvent. We use the REG-IQA method, which is a quantum topological energy decomposition (Interacting Quantum Atoms, IQA) coupled to a chemical-interpretation calculator (Relative Energy Gradient, REG). We focus on the rate-limiting addition step in order to unravel the different events taking place in this step, and understand the influence of solvent on the reaction, with an eye on predicting the Mayr electrophilicity. For the first time a link is established between an REG-IQA analysis and experimental values.
Pt Nanoparticles on Beta zeolites for Catalytic Toluene Oxidation: Effect of the Hydroxyl Groups of Beta Zeolite
Stabilisation of metal species using hydroxyl-rich dealuminated zeolites is a promising method for catalysis. However, insights into the interactions between the hydroxyl groups in zeolite and noble metals and their effects on catalysis are not yet fully understood. Herein, comparative studies were conducted using Pt catalysts supported on hydroxyl-rich dealuminated Beta (deAl-Beta) and the pristine proton-form Beta (H-Beta) for catalytic oxidation of toluene. The findings suggest that during impregnation the Pt precursor (i.e., Pt(NH3)4(NO3)2) interacted with different sites on deAl-Beta and H-Beta, leading to the formation of supported Pt nanoparticles with different physicochemical properties. The resulting Pt/deAl-Beta exhibited improved activity and anti-coking ability than Pt/H-Beta in catalytic toluene oxidation. According to toluene-TPD, 1H NMR relaxation and in situ DRIFTS characterisation, the enhanced performance of Pt/deAl-Beta could be ascribed to (i) the active Pt-O sites stabilised by hydroxyl groups, which interact with toluene easily for conversion, and (ii) the acid-free feature of the deAl-Beta support, which avoids the formation of coke precursors (such as benzoate species) on the catalyst surface. Findings of the work can serve as the design guidelines for making effective supported metal catalysts using zeolitic carriers.
Biomass Simulation: Orange and Eucalyptus Waste as a Source of Essential Oils Using Solar Energy
Residues from orange processing and wood production industries wastes can be valorized as feedstocks for the production of essential oils. A simultaneous extraction process of essential oils from orange peels and eucalyptus leaves by integrating solar thermal energy was designed and simulated. Scaling the process according to waste availability in the region of interest became possible.
Abstract
Orange processing and wood production industries generate wastes in the form of orange peel and eucalyptus leaves. These residues can be valorized as feedstocks to produce essential oils. Therefore, a simultaneous orange peel and eucalyptus leaves essential oil extraction process integrating solar energy was simulated. Biomass and essential oils were simulated by using equivalence models. The coupling of solar collectors allowed the extraction of eucalyptus essential oil, with a saving of 10 % in the total energy load.
Density Functional Theory Computations and Experimental Analyses to Highlight the Degradation of Reactive Black 5 Dye
Oxidative degradation of Reactive Black 5 (RB5) in aqueous solution was studied for Fenton process (FP), photo FP, sono FP, and sono photo FP. Reactivities of the studied chemical systems were analyzed by DFT calculations. Especially the calculated chemical hardness reflects the reactivity of dye and dye-Fe2+ complex. The experimental method used here provides high efficiency in the removal of RB5.
Abstract
The oxidative degradation of Reactive Black 5 (RB5) in aqueous solution was investigated using Fenton (FP), photo Fenton (P-FP), sono Fenton (S-FP), and sono photo Fenton (S-P-FP) processes. Degradation experiments showed efficient dye degradation for FP, P-FP, S-FP, and S-P-FP under optimal conditions. The half-life values of the reaction calculated for first-order reaction kinetics showed that the S-FP process is faster than the FP and P-FP processes. Using DFT calculations, the chemical reactivities of the studied chemical systems were analyzed. Especially the calculated chemical hardness values reflect the reactivities of the dye and the dye-Fe2+ complex. The calculated binding energy between the Fe2+ ion and RB5 of 15.836 eV is compatible with the prediction made in the light of the principle of hard and soft acids and bases. The computed data supported the experimental observations.
Nanomaterial‐Incorporated Membrane Distillation Membranes: Characteristics, Fabrication Techniques, and Applications
A thorough overview of the recent developments in membrane modification by incorporation of different types of nanoparticles in polymeric membranes resulting in improved fouling resistance and membrane wettability is given. Membrane modifications and membrane fabrication techniques, advanced membrane preparation using nanoscale materials, and future research are evaluated and discussed.
Abstract
Membrane distillation (MD), a temperature-driven membrane separation process, is used for various applications due to its less complicated design. MD operations encounter major issues such as permeate flux decrease, membrane fouling, and wetting. A lot of research has been conducted in the past years on the modification of MD membranes by incorporating nanomaterials to overcome these obstacles and considerably increase their performance. Nanomaterials incorporated into the membranes improve the water permeability, mechanical strength, and fouling. The incorporation of next-generation nanomaterials like metal oxide nanoparticles, carbon-based nanomaterials, graphene-based membranes, quantum dots, and metal-organic frameworks in the MD membranes is investigated. Essential membrane properties for MD operations are comprehensively studied, including higher liquid entry pressure, permeability, porosity, hydrophobicity, thermal stability, mean pore size, and low fouling rate. Significant advances in the application of nanomaterials to the modification of MD membranes as well as other membrane fabrication techniques adopted for the incorporation of nanoparticles like surface grafting, interfacial polymerization, plasma polymerization, and dip coating are reviewed. Important future aspects are discussed.
Modulating Catalyst‐Reactant Interface Microenvironment for Efficient Photocatalysis on Bismuth Sulfide
To improve the compatibility of the catalyst-pollutant interface, a polyvinylpyrrolidone (PVP)-capping strategy for enhanced photocatalysis of rhodamine B (RhB) on one-dimensional rod-like Bi2S3 nanocrystals was developed. This work provides an interface microenvironment modulation strategy for improving the photocatalytic performance of photocatalysts towards organic dyes.
Abstract
Pollution by organic dyes has received extensive attention due to their high toxicity, biohazard, and high stability in the natural environment, and the development of high-efficiency dye degradation and heavy metal ion reduction technologies is urgently needed in photocatalysis. However, the interface microenvironment between catalyst and pollutant is often ignored, and the poor compatibility of the catalyst-pollutant interface constrains further efficient catalysis. Herein, to improve the compatibility of the catalyst-pollutant interface, a surfactant-capping strategy for enhanced photocatalysis of rhodamine B (RhB) on one-dimensional rod-like Bi2S3 nanocrystals was investigated. Specifically, polyvinylpyrrolidone (PVP)-capped Bi2S3 (Bi2S3-PVP) showed enhanced RhB degradation rate compared with pure Bi2S3, and further studies suggested enhanced reaction interface compatibility at the Bi2S3-PVP-RhB interface. This work provides an interface microenvironment modulation strategy for improving photocatalytic performance towards organic dyes.
Overview Contents: Chemie Ingenieur Technik 10/2023
Chemical Engineering &Technology, Volume 46, Issue 10, Page 2259-2259, October 2023.