Theoretical investigation of the mechanism, chemo- and stereospecifity in the epoxidation reaction of limonene with meta-chloroperoxybenzoic acid (m-CPBA)

The epoxidation of limonene 1 with m-CPBA has been examined within the MEDT at the B3LYP/6-311(d,p) computational level. The chemo- and stereoisomeric reaction paths involving the two C=C double bonds of limonene have been scrutinized. DFT computations account for the high chemospecifity involving the C1=C2 double bond and the stereospecifity, in complete conformity with the experimental results. An ELF analysis of the epoxidation shows the formation of the epoxide ring taking place of the two new C-O single bonds is somewhat asynchronous

The regio- and stereoselective addition of dibromocarbene and dichlorocarbene onto β-himachalene

In this work we used DFT B3LYP/6-31G (d) to study the mechanism, the regio- and stereoselectivity of the [1+2] cycloaddition reaction between β-himachalene and dihalogenocarbene. Analysis of the reactivity indices and calculation of the activation energies of the transition states showed that this reaction is stereoselectives, the treatment of β-himachalene with one equivalent of dibromocarbene leads via an exothermic reaction to the formation of a single product P1 resulting from the attack of the most substituted double bond C6=C7 of β-himachalene. Treatment of product P1 with one equivalent of dichlorocarbene leads, again via an exothermic reaction, to formation of the two products P3 and P4, but dibromocarbene does not react with the product P1 due to the high activation energy of this reaction

Understanding the Regioselectivity and Reactivity of Friedel–Crafts benzoylation Using Parr Functions

A theoretical study of the reactivity and regioselectivity of some aromatic compounds in electrophilic aromatic substitution is carried out at the B3LYP/6-31G(d) computational level. The relative reactivity of these systems is rationalized by means of the global nucleophilicity index proposed by Domingo’s group. The positional selectivity, namely o, m or p, is predicted by means of the local nucleophilicity indices [Parr fonctions]. The present study shows that the experimental trends of the relative reactivities and regioselectivities of these reactions are correctly predicted using Parr fonctions

(4aS,10aS)-7-Hydr­oxy-8-isopropyl-1,1,4a-trimethyl-1,2,3,4,4a,9,10,10a-octa­hydro­phenanthrene: a new diterpenoid compound

The new title diterpenoid compound, C20H30O, is a natural product isolated from Tetra­clinis articulata wood via chloro­form extraction. The asymmetric unit contains four mol­ecules with the same S,S configuration, deduced from the chemical synthesis. Indeed, an overlay analysis, calculated using structure-matching software, shows that the four mol­ecules can be superimposed. The central ring has a half-chair conformation, whereas the saturated ring displays a chair conformation

Unveiling the reactions of triethylphosphite and its diethylamino substituted derivatives to carbon tetrachloride with a molecular electron density theory perspective

127-135A molecular electron density theory study is presented herein for the reactions of triethylphosphite (TEP) and its diethylamino substituted derivatives (DEAP and MEAP) to carbon tetrachloride (CCl4). Analysis of the Electron localization function (ELF) has allowed characterizing the electronic structure of the reagents and the conceptual density functional theory (CDFT) study predicted the polar character of the reactions with the electronic flux from TEP, DEAP and MEAP to CCl4. Analysis of the relative energies along the potential energy surfaces has indicated energetically favoured attack on the chlorine atom of CCl4 relative to that on the carbon atom and the reactions became energetically more facile due to introduction of the electron donating diethylamino substituent. This allowed formulating the heterolytic mechanism of the reactions in which the quick exchange of CCl3- with the chlorine atom takes place for TEP, while the exchange is sloweddown in DEAP and MEAP due to mesomeric stabilization of the phosphonium ion. The ELF and Atoms in molecules (AIM) studies indicated early transition states (TSs) with no new covalent bond formation, and the non-covalent interactions at the interatomic bonding regions of the TSs are analysed from the Independent Gradient Model (IGM) analysis based on the Hirshfield partition of electron density

Synthesis of some ribonucleosides derivatives and molecular docking analysis against variant corona virus omicrone

In this work, ribonucleoside products have been prepared by employing stannic tetrachloride (SnCl4) and natural phosphate as catalysts. The obtained result suggests that this catalyst facilitates the reactions of ribonucleoside-like products in a stereo-controlled manner, exhibiting β-selectivity when reacting with trimethylsilyl uracil, the ribonucleosides derivatives were obtained in suitable yields. In addition, we have performed the molecular docking analysis, demonstrated that the synthesized compounds have potential for antiviral activity against the omicron variant of coronavirus, and the D3, D4, E and F products have a higher binding energy than the molnupiravir drug, indicating that these products may be a probable drugs for the omicron variant

Molecular docking, elucidating the regiospecificity and the mechanism of [3+2] cycloloaddition reaction between azidobenzene and propiolaldehyde

Molecular electron density theory has been performed with the B3LYP/6-31(d,p) method to study the [3+2] cycloaddition processes between azidobenzene and propionaldehyde, the reactivity indices, activation and reaction energies are computed. The reaction and activation energies indicate that this [3+2] cycloaddition reaction is regiospecific, in good agreement with the experimental results. ELF examination revealed that the mechanism of these cycloaddition reactions takes place in two steps. In addition, a docking approach was performed on the products investigated, and the interaction with the protein protease COVID-19 (PDB ID: 6LU7), the results confirm that the presence of triazole and isoxazole rings increases the affinity of these products

Relevance of soil fertility spatial databases for parameterizing APSIM-wheat crop model in Moroccan rainfed areas

peer reviewedCrop models have evolved over the past decade to incorporate more soil-related processes. While this may open avenues to support farmers regarding fertilization practices, it also widens the pitfalls related to model parametrization. Open-access georeferenced soil databases are often a solution for modelers to derive soil parameters. However, they can potentially add to model uncertainty depending on database resolution and the variability of the characteristics it contains. Fertimap is an online spatial database recently released in Morocco. In this study, we aim at assessing how Fertimap could support the use of crop model in the rainfed wheat production areas of Morocco. Data including local soil analysis, farmers’ practices, wheat biomass, and yield were collected on 126 farmers’ fields distributed across the rainfed wheat production area in Morocco from 2018 to 2020. Data were first used to parameterize, calibrate, and assess the model, using site-specific data to infer soil parameters. Then, the impact of soil data source on model uncertainty was assessed by rerunning the simulations while using alternatively locally measured soil inputs or inputs extracted from Fertimap. To disentangle the effect of data source from model sensitivity on model outputs, the model’s sensitivity to labile phosphorus, pH, and organic carbon parameters was also tested. The APSIM-wheat model was found to reasonably simulate wheat phenological stages, biomass, and yield. The comparison of model outputs using one or another source of soil data indicated that using Fertimap had no significant effect on the model’s outputs. This study provides the first assessment of the APSIM-wheat model for simulation of widely used wheat cultivars in Moroccan rainfed areas. It is also the first proof of the practical utility of Fertimap database for modeling purposes in Morocco. This preliminary study delivers a robust basis for model-assisted agricultural advising to take off in Morocco

Reactions de cycloaddition chez les derives de l'acide ethenesulfonique

SIGLECNRS T 57535 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

A mechanism study and an investigation of the reason for the stereoselectivity in the [4+2] cycloaddition reaction between cyclopentadiene and gem-substituted ethylene electrophiles

The Molecular Electron Density Theory is applied to the [4+2] cycloaddition reaction between cyclopentadiene and gem-substituted ethylene electrophiles. Calculations are made for reactions, activation energies, and reactivity indices. The results of the experiment are perfectly consistent with activation energies, which unequivocally show that this cyclization’s are is highly stereoselective, in addition, based on ELF examination, the mechanism of these [4+2] cycloadditions occurs in two phases, The mechanisms of these reactions demonstrate that the term "pericyclic reaction" is no more relevant in the 21st century and has been replaced by the term "pseudocyclic"