Adeilton Pereira Maciel

Glycerol is a co-product of biodiesel production and an important raw material for the synthesis of economically and ecologically valuable compounds. The etherification of glycerol with benzyl alcohol is a promising chemical route that leads to the formation of highly volatile mono- and diethers with low viscosity and polarity. These compounds can be used as fuel additives to improve physicochemical properties, representing an alternative to increasing the biodiesel content in commercial diesel. Therefore, accurate and reliable protocols are required for the identification and quantification of the reaction products. In this study, a high-performance liquid chromatography method with ultraviolet-visible detection (HPLC-UV-Vis) was developed and validated to identify and quantify two ethers produced by glycerol benzylation. Method validation was carried out in accordance with Brazilian legislation and allowed efficient separation of the target compounds, here referred to as ether 1 and ether 2, showing satisfactory linearity in the concentration range of 150 to 400 µg mL-1, coefficients of determination of 0.9963 and 0.9990, and average recoveries of 105 and 74%, respectively. The method demonstrated accuracy, precision, and simplicity, proving suitable for monitoring the formation of glycerol ethers.

In this work, we conducted a theoretical investigation of the esterification of lauric acid (C12) with the natural unsaturated alcohol (-)-α-bisabolol, considering both uncatalyzed and CeO2-catalyzed pathways. Molecular structures were optimized using a combination of semi-empirical methods and Density Functional Theory (DFT), enabling the calculation of key parameters such as dipole moments, electrostatic potential maps, infrared spectra, and frontier molecular orbitals (HOMO and LUMO). For the uncatalyzed reactions, we evaluated thermodynamic descriptors, including enthalpy (∆H⁰), Gibbs free energy (∆G⁰), and entropy (∆S⁰), to gain mechanistic insights. Reaction pathways were further explored through a hybrid QM/MM strategy combined with Molecular Dynamics (MD) simulations. The esterification of lauric acid with (-)-α-bisabolol proceeds via an SN2-type mechanism. The findings indicate that, in the absence of a catalyst, the reaction is not spontaneous; however, the use of CeO2 as a heterogeneous catalyst significantly enhances the spontaneity, favoring the formation of (-)-α-bisabolol laurate.

The present paper performed for the first time the characterisation and ethanolization of ariri coconut oil catalysed by the lipase Burkholderia cepacia. Through the Complete Factor Planning 3² and the Response Surface Methodology (MSR), the effects of different molar ratios of oil/ethanol (1:4, 1:6, and 1:9) and catalytic loads (2%, 5%, and 10%) were evaluated, using B. Cepacia in free and immobilised form, in a reaction time of 4 h. The chemical characterisation of the ariri coconut oil showed the predominance of saturated fatty acids (78.52%), with lauric acid (C12:0) being the majority at 31.65%. Ariri coconut oil showed typical characteristics of vegetable oils suitable for enzymatic transesterification. The experimental results showed that the best ethyl ester content (67.1%) was obtained with the lipase immobilised, with a catalytic load of 2% and in the oil/ethanol ratio of 1:4. For reactions employing the free lipase, the best results (62.8%) were obtained with a catalytic load of 10% and in the oil/ethanol ratio of 1:6. The statistical analyses indicated that the catalytic load was the most significant variable for the reactions with the free lipase. In contrast, the oil/ethanol ratio was the most significant variable for the reactions with the immobilised lipase. The results of this study establish ariri coconut oil as a innovative and promising substrate for applications in transesterification reactions.

Syagrus cocoides Martius is a palm tree species. Its fruits are composed of an oily almond, until now restricted only to popular use. On the basis of that, to contribute scientific information about this plant, this work evaluated the physical Ariri coconut characteristic, the physical–chemical specifications of almond oil, and its potential to selectively obtain the lauric methyl ester from the transesterification oil reaction. Cold and hot oil extraction was performed using hexane as solvent, producing 18% and 14%, respectively. Alkaline transesterification was conducted for 1 h, and total conversion was observed. Conducting the ester separation by classic column chromatography, the effective isolation of lauric methyl ester in a 93% purity and 27% isolated yield was obtained. The results of this study contribute to knowledge regarding an under‐explored species. Furthermore, they facilitate the development of sustainable methodologies for obtaining valuable oleochemical products. Practical Applications : This study demonstrates the potential of the Ariri coconut as an alternative source of oil and raw material for the production of standard lauric methyl ester, a substance of high commercial value. The findings of this study indicate that Syagrus cocoides Martius, Ariri, is a promising species due to its comparable oil content to other palm species, suggesting the potential for the production of various fatty acid esters. The fractionation of lauric acid ester by column chromatography was effective and selective, indicating a new route for the production of analytical standards or inputs for the fine chemicals industry.

Transesterification is an essential process in bioproduct production, with catalyst choice being critical for reaction efficiency and selectivity. Lipases are effective biocatalysts due to their specificity and mild reaction conditions. This study employed computational chemistry and laboratory experiments to compare the enzymatic transesterification of ariri coconut oil with α-bisabolol and ethanol. Computational analyses using molecular dynamics (MD) and quantum mechanics/molecular mechanics (QM/MM) evaluated reaction stability and efficiency. The transesterification reactions carried out in the laboratory were carried out under different conditions using Burkholderia cepacia lipase as a biocatalyst. The products were analyzed by thin-layer chromatography (TLC). Computational results indicated that the activation energy (ΔG‡) for the reaction with α-bisabolol exceeded 20 kcal/mol, while for ethanol, it was 19.2 kcal/mol, suggesting a lower energy barrier for ethanol. Gibbs free energy (ΔG) was over 20 kcal/mol for α-bisabolol and 13 kcal/mol for ethanol, confirming ethanol as more energetically favorable. Laboratory tests showed product formation only in reactions with ethanol, aligning with computational findings. These results demonstrate ethanol’s efficiency for enzymatic transesterification of ariri oil. This paper contributes to bioproduct innovation by fostering sustainable processes, leveraging local natural resources, and integrating advanced biocatalysis and computational chemistry techniques.

Studies for clean fuels are interesting for the development of research through the processing of oils and fats, consisting of fatty acids, with high energy power and capable of conversion to esters (biodiesel), in transesterification or esterification reactions with homogeneous, heterogeneous catalysis, enzymatic. Basic homogeneous catalysis is the most widely used way of obtaining biodiesel, however it requires refined raw material and is free of water. In addition, the commonly used catalysts (NaOH, KOH, etc.) are aggressive to the environment and require a neutralization step. Heterogeneous catalysts have been shown to be efficient in transesterification reactions, because in addition to being reusable and not requiring a neutralization step after the reaction, they also have great economic viability. The considerations reported demonstrate the potential of heterogeneous catalysts in transesterification reactions, highlighting economic, technological and environmental aspects; and reinforce the need for incentives and research.

A química computacional emerge como uma área indispensável na ciência moderna, integrando conceitos de química, física, matemática e ciência da computação para estudar e prever estruturas, propriedades e comportamentos moleculares. Este artigo de revisão aborda os principais métodos utilizados na área, classificados em Ab initio, teoria do funcional da densidade (DFT), semiempíricos e empíricos, destacando suas características, avanços históricos. Os métodos Ab initio e DFT, baseados em princípios da física quântica, fornecem cálculos precisos para sistemas moleculares complexos, embora apresentem alto custo computacional. Já os métodos semiempíricos, ao combinar dados experimentais com teorias simplificadas, oferecem alternativas econômicas para simular respostas e propriedades moleculares. Métodos empíricos, como mecânica molecular (MM) e dinâmica molecular (DM), complementam essa abordagem, permitindo o estudo de sistemas macromoleculares e dinâmicas temporais. Os avanços recentes incluem o desenvolvimento de métodos híbridos, como mecânica quântica/mecânica molecular (QM/MM), que integram diferentes abordagens para lidar com sistemas amplos e complexos. As aplicações da química computacional abrangem desde a catálise química até a biotecnologia e a ciência dos materiais, demonstrando seu impacto em áreas como nanotecnologia. Embora desafios, como os altos custos computacionais e a necessidade de maior precisão, ainda persistem, os avanços em hardware e algoritmos sinalizando um futuro promissor. Este artigo reafirma a relevância da química computacional como uma ferramenta estratégica para o progresso científico.

Electron microscopy has become increasingly essential as an investigative research resource in various fields of science. Despite the evolution of the equipment and preparation techniques, little has been published on techniques for affixation and removal of samples on the stubs after analysis. This work aims to illustrate a quick and low‐cost procedure for fixing and removing a sample from the support for analysis by electronic microscopy, applied to crustacean and insect species, as well as other invertebrates. It thus makes it feasible to use specimens or anatomical portions of specimens represented by a few individuals, or designated as paratypes or holotypes in a collection.Research Highlights: This study presents a quick and low‐cost procedure for fixing and removing samples from support for electron microscopy analysis. This technique makes it possible to use individual specimens or anatomical portions represented in a collection. Fluidization of the adhesive and its complete removal allow easy recovery and repositioning of samples.