Grand Canonical Adaptive Resolution Simulation for Molecules with Electrons: A Theoretical Framework based on Physical Consistency

A theoretical scheme for the treatment of an open molecular system with electrons and nuclei is proposed. The idea is based on the Grand Canonical description of a quantum region embedded in a classical reservoir of molecules. Electronic properties of the quantum region are calculated at constant electronic chemical potential equal to that of the corresponding (large) bulk system treated at full quantum level. Instead, the exchange of molecules between the quantum region and the classical environment occurs at the chemical potential of the macroscopic thermodynamic conditions. T he Grand Canonical Adaptive Resolution Scheme is proposed for the treatment of the classical environment; such an approach can treat the exchange of molecules according to first principles of statistical mechanics and thermodynamic. The overall scheme is build on the basis of physical consistency, with the corresponding definition of numerical criteria of control of the approximations implied by the coupling. Given the wide range of expertise required, this work has the intention of providing guiding principles for the construction of a well founded computational protocol for actual multiscale simulations from the electronic to the mesoscopic scale.Comment: Computer Physics Communications (2017), in pres

Sustainable Production of Acetonitrile from Microalgae via Catalytic Fast Pyrolysis with Ammonia over Ga/HZSM‑5 Catalysts

We report on catalytic fast pyrolysis microalgae under ammonia atmosphere into acetonitrile over Ga/HZSM-5, which provides a long-term sustainable option for acetonitrile production and microalgae valorization. The effect of various catalysts, reaction conditions and species of microalgae on acetonitrile production was explored systematically. Under the optimized conditions, the maximum carbon yield of acetonitrile from Chlorella vulgaris was 23.4%, and the selectivity of acetonitrile in bio-oil was up to 77.2%. The possible reaction pathways were proposed according to the comprehensive experimental investigation on the conversion of model compounds and intermediates (proteins, carbohydrates, lipids, amino acids, carboxylic acids, furans, and amines). High-resolution transmission electron microscopy (TEM) analysis showed that Ga was present mainly at the outer surface of zeolite crystals, and a small amount of Ga was doped into the zeolite crystals

Catalytic Cleavage of the C–O Bond in Lignin and Lignin-Derived Aryl Ethers over Ni/AlP<i>_y</i>O<i>_x</i> Catalysts

The conversion of lignin into value-added chemicals is one of the important ways for sustainable development. Herein, phytic acid, a biomass-derived chemical, was used as the phosphorus source and pore former to synthesize the AlPyOx support. After loading Ni, the Ni/AlPyOx catalysts were found to be highly active in the catalytic conversion of lignin model compounds to high-value-added chemicals under mild conditions. The benzyl phenyl ether (α-O-4 lignin model compound) could be completely converted into toluene and phenol with near-equivalent selectivity at 30 °C and 3 MPa H2. Diphenyl ether and 2-phenoxy-1-phenylethanol were also used as 4-O-5 and β-O-4 model compounds of lignin, respectively. The unique activity of Ni/AlP0.5Ox could be attributed to metallic Ni that interacts with AlP0.5Ox and the unique adsorption of substrates on the carrier. Lignin can also be degraded over Ni/AlP0.5Ox via selective cleavage of the C–O bond, and 26.60 wt % yield of identified monomers was obtained

Oxalic Acid Monothioester for Palladium-Catalyzed Decarboxylative Thiocarbonylation and Hydrothiocarbonylation

Oxalic acid monothioester (OAM), an easily accessible and storable reagent, was reported herein as a thioester synthetic equivalent for palladium-catalyzed decarboxylative thiocarbonylation of organohalides and hydrothiocarbonylation of unsaturated carbon–carbon bonds at room temperature with high chemo- and regioselectivity. The reaction is applicable to the synthesis of cysteine-derived thioesters, thus allowing chemical modification of cysteine-containing peptides. Decarboxylation of OAM proceeds through oxidative addition of Pd(0) to the acyl–S bond, which accounts for the very mild reaction conditions

Photoredox-Catalyzed Allylic Defluorinative Alkoxycarbonylation of Trifluoromethyl Alkenes through Intermolecular Alkoxycarbonyl Radical Addition

The gem-difluoroalkene moiety is an ideal carbonyl bioisostere in medicinal chemistry, but efficient synthesis of β-gem-difluoroalkene esters remains challenging so far. Herein, we disclose a photoredox-catalyzed allylic defluorinative alkoxycarbonylation of trifluoromethyl alkenes enabled by intermolecular alkoxycarbonyl radical addition. A wide variety of alcohol oxalate derivatives were amenable, affording various β-gem-difluoroalkene esters with excellent functional group tolerance. Notably, the potential synthetic value of this method is highlighted by successful late-stage modification for bioactive molecules

Theoretical Study of Ir-Catalyzed Chemoselective C1–O Reduction of Glucose with Silane

Density functional theory (DFT) calculations have been performed to study the mechanism of Ir­(III) pincer complex (POCOP)­Ir­(H)­(acetone)⁺ (POCOP = 2,6-bis­(dibutylphosphinito)­phenyl) catalyzed chemoselective C1–O hydrosilylative reduction of glucose. The mechanisms for reduction of the external and internal C1–O (i.e., C1–O^ext and C1–O^int) on the C1-MeO-substituted glucose (i.e., <b>1</b>_<b>Me</b>) and C1–Me₂EtSiO-substituted glucose (i.e., <b>1</b>_<b>Si</b>) have been investigated. The calculation results show that both mechanisms proceed with the first concerted silyl transfer and the subsequent C1–O^ext or C1–O^int bond cleavage and hydride transfer steps. In the hydride transfer step, the Ir-H moiety acts as the hydride source. The C1–O cleavage is the rate-determining step of the overall mechanism. The C1–O^ext reduction is more favorable than C1–O^int reduction for the substrate <b>1</b>_<b>Me</b>, while the C1–O^int reduction is more favorable for <b>1</b>_<b>Si</b>. These results are consistent with the recent experimental outcomes. Analyzing the origin of chemoselectivity for the C1–O^ext or C1–O^int cleavage, we found that the more stable precursor of C1–O^ext cleavage and retention of the six-membered-ring structure result in the selective C1–O^ext reduction of <b>1</b>_<b>Me</b>. Meanwhile, the higher basicity of the alkyl ether O^int atom (in comparison to the silyl ether O^ext atom) and greater steric hindrance in the precursor favor the C1–O^int bond weakening. Therefore, the C1–O^int reduction occurs selectively for <b>1</b>_<b>Si</b>

Integrated Production of Aromatic Amines and N‑Doped Carbon from Lignin via <i>ex Situ</i> Catalytic Fast Pyrolysis in the Presence of Ammonia over Zeolites

Due to the irregular polymeric structure and carbon based inactive property, lignin valorization is very difficult. In this study we proposed a new route for lignin valorization by which aromatic amines can be directly produced from lignin by <i>ex situ</i> catalytic fast pyrolysis with ammonia over zeolite catalysts. Meanwhile, the obtained pyrolytic biochar can be activated to produce high surface area N-doped carbon for electrochemical application. Wheat straw lignin served as feed to optimize the pyrolysis conditions. MCM-41, β-zeolite, HZSM-5, HY, ZnO/HZSM-5, and ZnO/HY were screened, and ZnO/HZSM-5 (2 wt % Zn, Si/Al = 50) showed the optimal reactivity for producing aromatic amines due to the desired pore structure and acidity. Temperature, residence time, and ammonia content in the carrier gas displayed significant effects on the product distribution. The maximum yield of aromatic amines was obtained at moderate temperatures around 600 °C, 0.57 s, and 75% ammonia in the carrier gas. Under the optimized conditions, the total carbon yields of pyrolytic bio-oil and aromatic amines were 9.8% and 5.6%, respectively. The selectivity of aniline in the aromatic amines was up to 87.3%. Moreover, the pyrolysis byproduct, biochar, was further activated by KOH at 800 °C under ammonia atmosphere for producing N-doped carbon with high surface area. The pyrolytic biochar and N-doped carbon were characterized by elemental analysis, SEM, XRD, nitrogen adsorption–desorption, and XPS. Cyclic voltammetry (CV) and galvanostatic charge–discharge were employed to investigate the electrochemical performance of pyrolytic biochar and N-doped carbon. The specific capacitance of N-doped carbon reached about 128.4 F g^–1

G3//BMK and Its Application to Calculation of Bond Dissociation Enthalpies

On the basis of systematic examinations it was found that the BMK functional significantly outperformed the other popular density functional theory methods including B3LYP, B3P86, KMLYP, MPW1P86, O3LYP, and X3LYP for the calculation of bond dissociation enthalpies (BDEs). However, it was also found that even the BMK functional might dramatically fail in predicting the BDEs of some chemical bonds. To solve this problem, a new composite ab initio method named G3//BMK was developed by combining the strengths of both the G3 theory and BMK. G3//BMK was found to outperform the G3 and G3//B3LYP methods. It could accurately predict the BDEs of diverse types of chemical bonds in various organic molecules within a precision of ca. 1.2 kcal/mol

Nickel-Catalyzed Regio- and Stereoselective Hydrocarboxylation of Alkynes with Formic Acid through Catalytic CO Recycling

By the combination of a Ni­(II) salt, a bisphosphine ligand, and a catalytic amount of carboxylic acid anhydride, atom-economic hydrocarboxylation of various alkynes with formic acid can be achieved with high selectivity and remarkable functional group compatibility, affording α,β-unsaturated carboxylic acids regio- and stereoselectively. Both terminal and internal alkynes are amenable substrates. A mechanism proceeding through carbon monoxide recycling in a catalytic amount is demonstrated to be crucial for the success of this transformation

Comprehensive Volumetric Property of Eco-Friendly Pressurized Fluids by Experimental, Theoretical Modeling, and MD Simulation for Sustainable Oil Extraction from Waste Rice Bran

A comprehensive investigation into the densities of eco-friendly pressurized fluids, including pressurized biobased ethanol, CO2-expanded ethanol (CXE), and supercritical CO2 (sc-CO2), is notably lacking. This research gap covers experimental, theoretical modeling, and molecular dynamics (MD) simulations. Moreover, there is limited research on the extraction of rice bran oil (RBO). We have comprehensively investigated the densities of these pressurized fluids, employing a combination of experimental, theoretical modeling, and MD simulation approaches, combined with eco-friendly fluid techniques, to extract RBO from the waste biomass of rice bran. We have first developed a novel pulse response method with curve fitting for the simultaneous determination of density and diffusivity in pressurized fluids. Initially, density measurements were conducted for pressurized CO2 and pressurized ethanol, showing strong agreement with literature data within 298.15–323.15 K and 1.97–25.09 MPa. Applying this method to CXE resulted in minimal deviation within 6.0–10.0 MPa at 313.15 K. Moreover, this study introduces new density data for CXE at 313.15 K. The data covers CO2 mole fraction x1 values from 0.18 to 0.88 at 15.0 MPa and from 0.4 to 0.95 at 20.0 MPa. These findings are significant, revealing density peaks near x1 = 0.7 and providing valuable insights for the first time. Simultaneously, the experimental densities were successfully correlated using the semiempirical equation, while PC-SAFT EoS accurately represented the density. MD simulations cover pressurized CO2, pressurized ethanol, CXE, and sc-CO2 densities over varied temperatures and pressures. The densities of CO2 were simulated by using four models: Cygan, EPM2, TraPPE, and Zhang. EPM2 proves most accurate with an average absolute relative deviation (AARD) of 5.5%, outperforming the other models. Ethanol densities were replicated using the OPLS-AA model with an AARD of 5.5%. The novel ReaxFF and CPMD models exhibited excellent agreement for CXE, with AARD of 1.90 and 1.38%, respectively. Furthermore, CPMD performed extremely well compared with classical MD simulation and ReaxFF for all pressurized fluids, particularly near the critical point of CO2 and the critical point of ethanol. Expanding on research into pressurized fluid properties, novel eco-friendly extraction methods employing pressurized ethanol, CXE, and sc-CO2 have been developed for RBO extraction from rice bran. Notably, the pioneering CXE technique demonstrates outstanding results with a remarkable 0.23 yield ratio achieved at 313.15 K, 20.0 MPa, and x1 = 0.7. These insights into pressurized fluid equilibrium and transport properties hold great potential for diverse environmentally friendly industrial applications