Next Issue
Volume 5, March
Previous Issue
Volume 4, September
 
 

Reactions, Volume 4, Issue 4 (December 2023) – 14 articles

  • Issues are regarded as officially published after their release is announced to the table of contents alert mailing list.
  • You may sign up for e-mail alerts to receive table of contents of newly released issues.
  • PDF is the official format for papers published in both, html and pdf forms. To view the papers in pdf format, click on the "PDF Full-text" link, and use the free Adobe Reader to open them.
Order results
Result details
Select all
Export citation of selected articles as:
10 pages, 1714 KiB  
Communication
Increased Yields of the Guanine Oxidative Damage Product Imidazolone Following Exposure to LED Light
Reactions 2023, 4(4), 801-810; https://doi.org/10.3390/reactions4040046 - 16 Dec 2023
Viewed by 978
Abstract
Among the bases of DNA, guanine is the most easily oxidized. Imidazolone (Iz) is a guanine oxidative damage, and we sought to generate Iz-containing oligomers. In this paper, we describe the methods and conditions to increase the yield of Iz by employing photooxidation [...] Read more.
Among the bases of DNA, guanine is the most easily oxidized. Imidazolone (Iz) is a guanine oxidative damage, and we sought to generate Iz-containing oligomers. In this paper, we describe the methods and conditions to increase the yield of Iz by employing photooxidation reactions using light-emitting diodes (LEDs) with emission wavelengths of 365 nm and 450 nm. For photooxidation performed with the 450 nm LED source at light intensities of 2.75–275 mW/cm2, peak yields of Iz were 35% at light intensities of 27.5 and 68.8 mW/cm2. For reactions performed with the 365 nm LED source at light intensities of 5.12–512 mW/cm2, the peak yield of Iz was 34% at a light intensity of 51.2 mW/cm2. By varying the irradiation time, the maximum yield of Iz (34–35%) was obtained with irradiation times of 5–20 min using the 450 nm LED source at an intensity of 13.8 mW/cm2. Using the 365 nm LED source at an intensity of 25.6 mW/cm2, the maximum Iz yield obtained was 31% at irradiation times of 2–5 min. Thus, we obtained conditions that can provide an Iz yield of up to 35%. Full article
(This article belongs to the Special Issue Feature Papers in Reactions in 2023)
Show Figures

Figure 1

22 pages, 5905 KiB  
Review
One-Pot Reactions of Triethyl Orthoformate with Amines
Reactions 2023, 4(4), 779-800; https://doi.org/10.3390/reactions4040045 - 02 Dec 2023
Viewed by 1640
Abstract
One-pot reactions offer advantages like easy automation, higher product yields, minimal waste generation, operational simplicity, and thus reduced cost, time and energy. This review presents a comprehensive overview of one-pot reactions including triethyl orthoformate and amines as valuable and efficient reagents for carrying [...] Read more.
One-pot reactions offer advantages like easy automation, higher product yields, minimal waste generation, operational simplicity, and thus reduced cost, time and energy. This review presents a comprehensive overview of one-pot reactions including triethyl orthoformate and amines as valuable and efficient reagents for carrying out two-, three- or four-component organic reactions. Full article
(This article belongs to the Special Issue Feature Papers in Reactions in 2023)
Show Figures

Figure 1

13 pages, 1628 KiB  
Review
Chlorophyll Sensitization of TiO2: A Mini-Review
Reactions 2023, 4(4), 766-778; https://doi.org/10.3390/reactions4040044 - 01 Dec 2023
Viewed by 1045
Abstract
Recent studies have shown that chlorophyll sensitization can improve the performance of semiconductors like TiO2 in photocatalytic reactions and light-harvesting technologies, such as solar cells. Faced with the search for renewable energy sources and sustainable technologies, the application of this natural pigment [...] Read more.
Recent studies have shown that chlorophyll sensitization can improve the performance of semiconductors like TiO2 in photocatalytic reactions and light-harvesting technologies, such as solar cells. Faced with the search for renewable energy sources and sustainable technologies, the application of this natural pigment has been gaining prominence. The present work addresses some of the main possibilities of chlorophyll-TiO2 combination, presenting the most relevant aspects affecting chlorophyll extraction and TiO2 sensitization. Full article
Show Figures

Figure 1

29 pages, 12509 KiB  
Review
Review on the Synthesis, Recyclability, Degradability, Self-Healability and Potential Applications of Reversible Imine Bond Containing Biobased Epoxy Thermosets
Reactions 2023, 4(4), 737-765; https://doi.org/10.3390/reactions4040043 - 01 Dec 2023
Viewed by 1203
Abstract
Epoxy thermosets need to be designed for simple recycling and biomass resource utilization in order to be fully sustainable building materials. The development of covalent adaptive networks (CANs) using adaptive covalent chemistry (ACC) may be helpful in this regard. Several reversible covalent bonds [...] Read more.
Epoxy thermosets need to be designed for simple recycling and biomass resource utilization in order to be fully sustainable building materials. The development of covalent adaptive networks (CANs) using adaptive covalent chemistry (ACC) may be helpful in this regard. Several reversible covalent bonds are incorporated into the epoxy polymer to overcome the challenge of reprocessability or recyclability, degradability and self-healability. The imine bond, also referred to as the Schiff base, is one of the reversible covalent bonds that can participate in both associative and dissociative reactions. This opens up possibilities for mechanical and chemical recycling as well as self-healing. This review summarises the progress related to the synthesis and mechanical and thermal properties of epoxy thermosets based on reversible imine bonds derived from different sustainable resources over the past few decades. The feedstocks, physical and thermal properties, recycling conditions, degradability and self-healability of the biomass epoxy thermosets are addressed along with the main obstacles, prospective improvements and potential applications. Full article
Show Figures

Figure 1

12 pages, 1496 KiB  
Article
A New Pd-Based Catalytic System for the Reductive Carbonylation of Nitrobenzene to Form N-(4-hydroxyphenyl)acetamide Selectively in One Pot
Reactions 2023, 4(4), 725-736; https://doi.org/10.3390/reactions4040042 - 17 Nov 2023
Viewed by 1263
Abstract
N-(4-hydroxyphenyl)acetamide (commonly named paracetamol or acetaminophen) is a target molecules for many industries that produce chemicals for pharmaceutical applications. The industrial processes, however, use multistep procedures with low overall yield and/or severe drawbacks and problems in terms of sustainability. In the present paper, [...] Read more.
N-(4-hydroxyphenyl)acetamide (commonly named paracetamol or acetaminophen) is a target molecules for many industries that produce chemicals for pharmaceutical applications. The industrial processes, however, use multistep procedures with low overall yield and/or severe drawbacks and problems in terms of sustainability. In the present paper, a one-pot synthesis is proposed based on the reductive carbonylation of nitrobenzene catalyzed by Pd(II)-complexes. Usually, such a reaction leads to a mixture of different products, including aniline, 4-aminophenol and 1,3-diphenylurea. However, the selectivity towards the possible products strongly depends by the ligands on the Pd(II)-catalyst, but also by the nature of the solvent. According to this, we have found that when the reaction was carried out in dilute acetic acid as a solvent, the [PdCl2(dppb)] catalyst precursor leads in one pot to N-(4-hydroxyphenyl)acetamide. Under optimized reaction conditions, it was possible to produce N-(4-hydroxyphenyl)acetamide with a 85 mol % of selectivity in ca. 5 h. Full article
Show Figures

Figure 1

12 pages, 2712 KiB  
Article
Silver Nanoparticles Coated with Recombinant Human Epidermal Growth Factor: Synthesis, Characterization, Liberation and Anti-Escherichia coli Activity
Reactions 2023, 4(4), 713-724; https://doi.org/10.3390/reactions4040041 - 15 Nov 2023
Viewed by 1105
Abstract
Epithelial tissue regeneration may be favored if the tissue receives both therapeutic agents such as recombinant human epidermal growth factor (rhEGF) and, simultaneously, antibacterial materials capable of reducing the risk of infections. Herein, we synthesized silver nanoparticles (AgNPs), which are well-known antibacterial materials, [...] Read more.
Epithelial tissue regeneration may be favored if the tissue receives both therapeutic agents such as recombinant human epidermal growth factor (rhEGF) and, simultaneously, antibacterial materials capable of reducing the risk of infections. Herein, we synthesized silver nanoparticles (AgNPs), which are well-known antibacterial materials, and impregnate them with rhEGF in order to study a bio-nanomaterial of potential interest for epithelial tissue regeneration. A suspension of Ag NPs is prepared by the chemical reduction method, employing sodium citrate as both a reducer and capping agent. The AgNPs suspension is mixed with a saline solution containing rhEGF, producing rhEGF-coated Ag NPs with rhEGF loadings between 0.1 and 0.4% w/w. ELISA assays of supernatants demonstrate that, in all studied cases, over 90% of the added rhEGF forms part of the coating, evidencing a high efficiency in impregnation. During the preparation of rhEGF-coated Ag NPs, no significant changes are observed on the nanoparticles, which are characterized by UV-Vis spectroscopy, transmission electron microscopy (TEM) and infrared spectroscopy. The liberation of rhEGF in vitro was followed for 72 h, finding that approximately 1% of rhEGF that is present is released. The rhEGF-coated AgNPs shows antibacterial activity against E. coli, although such activity is decreased with respect to that observed from naked AgNPs. Having confirmed the possibility of simultaneously liberating rhEGF and reducing the proliferation of bacteria, this work helps to support the use of rhEGF-loaded metallic nanoparticles for tissue regeneration. Full article
(This article belongs to the Special Issue Nanoparticles: Synthesis, Properties, and Applications)
Show Figures

Figure 1

11 pages, 2231 KiB  
Article
Experimental Control of a Methanol Catalytic Membrane Reformer
Reactions 2023, 4(4), 702-712; https://doi.org/10.3390/reactions4040040 - 06 Nov 2023
Viewed by 1247
Abstract
A simple proportional integral (PI) controller with scheduled gain has been developed and implemented in a catalytic membrane reactor (CMR) to obtain pure hydrogen from a methanol steam reforming process. The controller is designed to track the setpoint of the pure hydrogen flow [...] Read more.
A simple proportional integral (PI) controller with scheduled gain has been developed and implemented in a catalytic membrane reactor (CMR) to obtain pure hydrogen from a methanol steam reforming process. The controller is designed to track the setpoint of the pure hydrogen flow rate in the permeate side of the CMR via the manipulation of the fuel inlet flow rate. Therefore, the controller actuator is the liquid pump that provides the mixture of methanol and water to the reactor. Within the CMR, the catalytic pellets of PdZn/ZnAl2O4/Al2O3 have been used to facilitate the methanol steam-reforming reaction under stoichiometric conditions (S/C = 1), and Pd–Ag metallic membranes have been employed to simultaneously separate the generated hydrogen. The PI controller design is based on a mathematical model constructed using transfer functions acquired from dynamic experiments conducted with the CMR. The controller has been successfully implemented, and experimental validation tests have been carried out at 450 °C and relative pressures of 6, 8, 10, and 12 bar. Full article
(This article belongs to the Special Issue Hydrogen Production and Storage, 2nd Edition)
Show Figures

Figure 1

23 pages, 5571 KiB  
Article
Glycerol Hydrogenolysis to Bio-Propanol: Catalytic Activity and Kinetic Model for Ni/C Modified with Al(H2PO4)3
Reactions 2023, 4(4), 679-701; https://doi.org/10.3390/reactions4040039 - 05 Nov 2023
Viewed by 1397
Abstract
The aim of the present research is to investigate the effect of different operation variables in the hydrogenolysis of glycerol to 1-propanol and to develop a simple kinetic model useful for the design of the reactor. For this purpose, a carbon-based composite was [...] Read more.
The aim of the present research is to investigate the effect of different operation variables in the hydrogenolysis of glycerol to 1-propanol and to develop a simple kinetic model useful for the design of the reactor. For this purpose, a carbon-based composite was impregnated with 4 wt.% of Al(H2PO4)3 (CPAl) and used as a support to prepare a Ni catalyst. The support and the catalyst were characterized by BET, XRD, NMR, potentiometric titration, isopropanol decomposition reaction, TEM and TPR analysis. The catalytic tests were carried out at 220–260 °C and 0.5–4 MPa of H2 initial pressure varying the glycerol concentration in aqueous solutions between 30 and 80 wt.%. The presence of aluminum phosphates in the Ni/CPAl catalyst moderates the surface acidity and the formation of Ni2P leads to a high selectivity towards 1-propanol. In this sense, the Ni/CPAl catalyst showed total glycerol conversion and 74% selectivity towards 1-propanol at 260 °C and 2 MPa of H2 initial pressure using 30 wt.% glycerol aqueous solution and 8 h of reaction time. A slight increase in particle size from 10 to 12 nm was observed after a first reaction cycle, but no changes in acidity and structure were observed. Based on these results, a power-law kinetic model was proposed. For glycerol consumption, partial orders of 0.07, 0.68 and −0.98 were determined with respect to glycerol, H2 and water, and an apparent activation energy of 89 kJ mol−1 was estimated. The results obtained indicate that the model fits the experimental concentration values well and can predict them with an average error of less than 7%. Full article
(This article belongs to the Special Issue Feature Papers in Reactions in 2023)
Show Figures

Figure 1

12 pages, 1766 KiB  
Review
Conversion of Biomass-Derived Molecules into Alkyl Levulinates Using Heterogeneous Catalysts
Reactions 2023, 4(4), 667-678; https://doi.org/10.3390/reactions4040038 - 01 Nov 2023
Cited by 1 | Viewed by 1330
Abstract
Alkyl levulinates are promising and versatile biomass-derived chemicals, which are utilized as fuel additives, flavoring agents, fragrances, solvents, and precursors for synthesizing valuable γ-valerolactone. A method for synthesizing alkyl levulinates involves the esterification of levulinic acid with the corresponding alkyl alcohols in [...] Read more.
Alkyl levulinates are promising and versatile biomass-derived chemicals, which are utilized as fuel additives, flavoring agents, fragrances, solvents, and precursors for synthesizing valuable γ-valerolactone. A method for synthesizing alkyl levulinates involves the esterification of levulinic acid with the corresponding alkyl alcohols in the presence of solid acid catalysts that have abundant Brønsted acid sites. Alkyl levulinates can also be synthesized from other biomass-derived molecules such as furfuryl alcohol and furfural via alcoholysis and one-pot conversion, respectively. Thus far, various heterogeneous catalysts have been developed for the conversion of the biomass-derived molecules (levulinic acid, furfuryl alcohol, and furfural) into alkyl levulinates. To obtain the target products in high yields, numerous strategies have been employed including increasing Brønsted acidity, dispersing and incorporating Brønsted acid sites, inducing the formation of mesopores, and inducing a synergistic effect of metal–Brønsted acid sites that are present on a catalyst surface. Here, we summarily reviewed the performances of the heterogeneous catalysts in the conversions, describing the design and development of the heterogeneous catalysts that ensured the excellent yield of alkyl levulinates. Full article
(This article belongs to the Special Issue Feature Papers in Reactions in 2023)
Show Figures

Figure 1

10 pages, 4841 KiB  
Article
Palladium-Catalyzed Cross-Coupling Reaction of Bis(cyclopentadienyl)diaryltitaniums with Terminal Alkynes
Reactions 2023, 4(4), 657-666; https://doi.org/10.3390/reactions4040037 - 19 Oct 2023
Viewed by 1129
Abstract
Organotitanium compounds find application in diverse reactions, including carbon–carbon bond formation and oxidation. While titanium (IV) compounds have been used in various applications, the potential of bis(cyclopentadienyl)diaryltitanium in cross-coupling reactions remains unexplored. This study focuses on Sonogashira-type cross-coupling reactions involving terminal alkynes and [...] Read more.
Organotitanium compounds find application in diverse reactions, including carbon–carbon bond formation and oxidation. While titanium (IV) compounds have been used in various applications, the potential of bis(cyclopentadienyl)diaryltitanium in cross-coupling reactions remains unexplored. This study focuses on Sonogashira-type cross-coupling reactions involving terminal alkynes and organotitanium compounds. Diaryltitanocenes were synthesized using titanocene dichloride with lithium intermediates derived from aryl iodide. Under open-flask conditions, reactions of diphenyltitanocenes with ethynylbenzene in the presence of 20 mol% Pd(OAc)2 in DMF produced coupling products in a remarkable 99% yield. Various diaryltitanocenes and alkynes under standard conditions yielded corresponding cross-coupling products with moderate to good yields. Notably, the Sonogashira-type alkynylation proceeds under mild conditions, including open-flask conditions, and without the need for a base. Furthermore, this cross-coupling is atom-economical and involves the active participation of both aryl groups of the diaryltitanocene. Remarkably, this study presents the first example of a Sonogashira-type cross-coupling using titanium compounds as pseudo-halides. Full article
(This article belongs to the Special Issue Feature Papers in Reactions in 2023)
Show Figures

Figure 1

10 pages, 1573 KiB  
Viewpoint
Inversely Finding Peculiar Reaction Conditions toward Microfluidic Droplet Synthesis
Reactions 2023, 4(4), 647-656; https://doi.org/10.3390/reactions4040036 - 16 Oct 2023
Viewed by 962
Abstract
With the development of microfluidics, there are increasing reports of syntheses using not only conventional laminar flow at the microscale, but also the dissociation and aggregation of microdroplets. It is known, to some extent, that the microfluidics scale differs from normal scales in [...] Read more.
With the development of microfluidics, there are increasing reports of syntheses using not only conventional laminar flow at the microscale, but also the dissociation and aggregation of microdroplets. It is known, to some extent, that the microfluidics scale differs from normal scales in terms of the specific surface area, mass diffusion, and heat conduction; these are opposite to those in scale-up in-plant chemical engineering. However, it is not easy to determine what changes when the microdroplet flows through the channel. In this context, the author would like to clarify how the behavior of chemical species, which is expected to appear unique at the nanoscale, contributes to chemical reactions. What do we need in order to develop a completely new theory of chemical reactions? The characteristics of chemical reactions on the nanoscale are clarified via the encountering of solutions by the microfluidic device itself, or the chemical reaction of nanoscale droplets generated by the microfluidic device. Specifically, in recent years, experimental reports have accumulated that are expected to develop a fluidic device that can stably generate nanodroplets, and complex reactions of different reactivity are expected to occur that are specific to the nanoscale. In this short article, microfluidic devices, nanoscale droplets, experimental synthetic examples, and findings that may provide solutions are described. Full article
(This article belongs to the Special Issue Feature Papers in Reactions in 2023)
Show Figures

Figure 1

12 pages, 7057 KiB  
Article
Confinement of LiAlH4 in a Mesoporous Carbon Black for Improved Near-Ambient Release of H2
Reactions 2023, 4(4), 635-646; https://doi.org/10.3390/reactions4040035 - 11 Oct 2023
Viewed by 1013
Abstract
LiAlH4 is a potential solid-state H2 storage material, where safe and efficient H2 storage is of critical importance for the transition towards a sustainable emission-free economy. To improve the H2 release and storage properties of LiAlH4, confinement [...] Read more.
LiAlH4 is a potential solid-state H2 storage material, where safe and efficient H2 storage is of critical importance for the transition towards a sustainable emission-free economy. To improve the H2 release and storage properties of LiAlH4, confinement in porous media decreases the temperature of H2 release and improves the kinetics, where considerably improved H2 release properties are accompanied by a loss in the total amount of H2 released. The capability of mesoporous carbon black to improve the H2 storage properties of confined LiAlH4 is investigated with temperature-programmed desorption and time-stability measurements using X-ray diffraction and N2 gas adsorption measurements to characterize the composite materials’ composition and structure. Here, we present the capability of commercial carbon black to effectively lower the onset temperature of H2 release to that of near-ambient, ≥295 K. In addition, the confinement in mesoporous carbon black destabilized LiAlH4 to a degree that during ≤14 days in storage, under Ar atmosphere and at ambient temperature, 40% of the theoretically contained H2 was lost due to decomposition. Thus, we present the possibility of destabilizing LiAlH4 to a very high degree and, thus, avoiding the melting step before H2 release at around 440 K using scaffold materials with fine-tuned porosities. Full article
(This article belongs to the Special Issue Hydrogen Production and Storage, 2nd Edition)
Show Figures

Figure 1

66 pages, 8444 KiB  
Review
Transformations of Glycerol into High-Value-Added Chemical Products: Ketalization and Esterification Reactions
Reactions 2023, 4(4), 569-634; https://doi.org/10.3390/reactions4040034 - 08 Oct 2023
Viewed by 1140
Abstract
Biomass allows us to obtain energy and high-value-added compounds through the use of different physical and chemical processes. The glycerol obtained as a by-product in the synthesis of biodiesel is considered a biomass compound that has the potential to be used as a [...] Read more.
Biomass allows us to obtain energy and high-value-added compounds through the use of different physical and chemical processes. The glycerol obtained as a by-product in the synthesis of biodiesel is considered a biomass compound that has the potential to be used as a raw material to obtain different chemical products for industry. The development and growth of the biodiesel industry allows for the projection of glycerol biorefineries around these plants that efficiently and sustainably integrate the biodiesel production process together with the glycerol transformation processes. This work presents a review of the ketalization and esterification of glycerol to obtain solketal and acetylglycerols, which are considered products of high added value for the chemical and fuel industry. First, the general aspects and mechanisms of both reactions are presented, as well as the related chemical equilibrium concepts. Subsequently, the catalysts employed are described, classifying them according to their catalytic nature (zeolites, carbons, exchange resins, etc.). The reaction conditions used are also described, and the best results for each catalytic system are presented. In addition, stability studies and the main deactivation mechanisms are discussed. Finally, the work presents the kinetic models that have been formulated to date for some of these systems. It is expected that this review work will serve as a tool for the advancement of studies on the ketalization and esterification reactions that allow for the projection of biorefineries based on glycerol as a raw material. Full article
Show Figures

Figure 1

17 pages, 5315 KiB  
Article
Multicomponent Reactions Promoted by Ecocatalyst from Metal Hyperaccumulating Plant Pluchea sagittalis
Reactions 2023, 4(4), 552-568; https://doi.org/10.3390/reactions4040033 - 07 Oct 2023
Viewed by 902
Abstract
Phytoremediation has been considered a sustainable environmental technology for heavy metals decontamination. In this work, we evaluated the metal contents by inductively coupled plasma optical emission spectrometry (ICP-OES) of three plant species collected in a mine in the Brazilian Amazonia area. Based on [...] Read more.
Phytoremediation has been considered a sustainable environmental technology for heavy metals decontamination. In this work, we evaluated the metal contents by inductively coupled plasma optical emission spectrometry (ICP-OES) of three plant species collected in a mine in the Brazilian Amazonia area. Based on this analysis, Pluchea sagitallis leaves were selected to prepare metallic ecocatalysts. The leaf ashes and the obtained ecocatalysts were characterized by ICP-OES, X-ray diffraction (XRD), scanning electron microscopy (SEM) and N2-physisorption measurements. Moreover, they were evaluated in the Biginelli and Hantzsch multicomponent reactions, furnishing the corresponding 3,4-dihydropyrimidin-2-(1H)-ones and 1,4-dihydropyridines with good to excellent yields. The best ecocatalyst was easily recovered and recycled in up to six reactions without a significant decrease in its performance. Full article
Show Figures

Figure 1

Previous Issue
Next Issue
Back to TopTop