Methoxy Methyl Research Articles

Mechanistic investigation of methanol-to-olefins conversion catalyzed by H-ZSM-5 zeolite: a DFT study.

The mechanisms for the formation of the first C - C bond and lower olefins on methanol to olefins (MTO) conversion on H-ZSM-5 had been focused in dispute. In this paper, density functional theory has been used to study the reaction mechanisms of methanol to olefins on ZSM-5. The configurations of reactants, intermediates, products and transition state of the numerous reactions involved in such a process have been optimized, as well as the elementary reactions related to these configurations were determined by the calculation of corresponding activation energy barriers and reaction heats. Here, two different kinds of the mechanisms were proposed for the formation of dimethylether (DME), one involving an associative interaction of two methanol molecules with the zeolite Brønsted acid sites and the other occurring via a surface methoxy species and a methanol molecule. A critical intermediate of the methoxy methyl cation was theoretically verified by the reaction of the methoxy species and dimethylether. Besides, it was found that the first intermediates containing a C - C bond were 1,2-dimethoxyethane and 2-methoxy-ethanolare, in which the former was formed from methoxy species with dimethyl ether and the latter was formed from methanol by onium ions((CH3)2O+CH2CH2OCH3), respectively. For the whole reaction mechanism, the results in this paper indicated that the ethene formation is more favorable than propylene formation due to the low activation energy barrier for ethene formation (123.49 vs. 162.09kJ.mol-1). From these calculations, it would be concluded that ethene is the first alkene product that induces the occurrence of the hydrocarbon pool mechanism. All the periodic density function theory (DFT) calculations were performed by the Vienna Ab Initio Simulation package (VASP). The interaction between nucleus and valence electron was described using the pseudopotentials found in the projector augmented wave (PAW) method. PBE-D3 was used in the whole DFT calculations and CI-NEB was used to locate transition state.

Sesquiterpene Cyclase BcBOT2 Promotes the Unprecedented Wagner-Meerwein Rearrangement of the Methoxy Group.

Presilphiperfolan-8β-ol synthase (BcBOT2), a substrate-promiscuous sesquiterpene cyclase (STC) of fungal origin, is capable of converting two new farnesyl pyrophosphate (FPP) derivatives modified at C7 of farnesyl pyrophosphate (FPP) bearing either a hydroxymethyl group or a methoxymethyl group. These substrates were chosen based on a computationally generated model. Biotransformations yielded five new oxygenated terpenoids. Remarkably, the formation of one of these tricyclic products can only be explained by a cationically induced migration of the methoxy group, presumably via a Meerwein-salt intermediate, unprecedented in synthetic chemistry and biosynthesis. The results show the great principle and general potential of terpene cyclases for mechanistic studies of unusual cation chemistry and for the creation of new terpene skeletons.

Total Synthesis of Carbazomycins E and F.

Total synthesis of carbazomycins E and F was achieved by double functionalization of an aryne intermediate generated from a 2-aminobiphenyl derivative. The tethered amino group underwent nucleophilic addition to the aryne intermediate to construct the carbazole skeleton. The resulting carbanion was formylated to give the multiply substituted carbazole. This formyl group caused several problems. For example, it was difficult to perform regioselective demethylation of the methoxy group proximal to the formyl group without protecting the carbazole nitrogen. In addition, the formyl group was unexpectedly reduced to give a methoxymethyl group under heating conditions with copper iodide and sodium methoxide. Oxidation of this compound in the presence of water was effective for obtaining the formylated carbazole, leading to the first total synthesis of carbazomycin F.

(2S)-2-(Difluoro(methoxy)methyl)pyrrolidine-1-sulfinyl fluoride as a new reagent in the Cl/F exchange reactions with aryl and alkyl sulfonyl chlorides

The reaction of (2S)-2-(difluoro(methoxy)methyl)pyrrolidine-1-sulfinyl fluoride with aryl, heteryl and alkyl sulfonyl chlorides provides a convenient synthetic route to sulfonyl fluorides. DFT calculations predict negative reaction energy values for the exchange reaction. The S-F bond energy is higher in the sulfonyl fluorides than that in sulfinyl fluorides.

Study on the mechanism of lignin and lignin-carbohydrate complex hydrolysis under alkaline conditions by density functional theory

Lignin hydrolyzes during alkali-heat pretreatment of lignocellulose, due to the cleavage of covalent linkages between lignin and lignin-carbohydrate complex. Various structure of lignin monomers are responsible of the complicated hydrolysis mechanism of lignin and lignin-carbohydrate complex. This study used density functional theory to reveal the hydrolysis mechanism of lignin with various substituents and lignin-carbohydrates complex with different linkages. The results indicated that the SN2 reaction was observed to take place in the lignin. Methoxy groups and methyl group had an insignificant influence on hydrolysis reaction pathway of lignin, whereas the presence of a methyl group on the α-carbon atom had a hindering effect on the nucleophilic attack during alkaline pretreatment. The lignin-carbohydrate complex with different linkage showed a significant difference in hydrolysis reaction pathway. Additionally, the reaction energy barrier of ester bond hydrolysis was lowest among the hydrolysis of ester bond, phenyl glycosidic bond, benzyl ether bond, γ-ester bond, coumarin ester bond and acetal bond under alkaline condition. This study provides valuable insights into the process control, reactor design, and performance enhancement for lignocellulose pretreatment.

Design and sustainable synthesis of small mannose-based glycodendrons as ligands for HIV-1 envelope protein gp120: Toward an explanation for their binding

On the basis of the interesting properties that glucuronic acid-based glycodendrimers and glycodendrons show against Dengue virus through their interaction with its envelope protein, herein we describe the design, sustainable synthesis and anti HIV-1 evaluation of a series of mannose-based glycodendrimers bearing different scaffolds, valency and functional groups at the focal position. Their sustainable chemical synthesis was performed using microwave-assisted copper(I) catalyzed azide-alkyne cycloaddition (CuAAC) reaction to yield glycoconjugates with full conversions (99%), allowing the reduction of the reaction time from 16 h to 60–120 min. Surface plasmon resonance studies have demonstrated that the small mannose-based glycodendrons (divalent derivatives) give the best binding interactions with the HIV-1 gp120 envelope protein, being the most active those that have a methoxymethyl group or an azidomethyl group at the focal position. Molecular modeling studies were carried out to simulate and explain the binding observed by surface plasmon resonance. This work reports a sustainable synthesis of small mannose-based glycodendrons as novel and potent anti HIV lead compounds.

Toward coherent anti‐Stokes Raman scattering‐Raman optical activity for reaction monitoring in organocatalysis: Chiral vibrational signatures of the two atropisomers (R)‐ and (S)‐MOM‐BINOL in solution

AbstractCoherent anti‐Stokes Raman scattering‐Raman optical activity (CARS‐ROA) is a coherent version of spontaneous ROA spectroscopy, the latter being a well‐established chirally sensitive vibrational spectroscopic technique. A central major advantage of heterodyne‐detected CARS‐ROA over ROA is the drastic reduction of acquisition times from several hours to approximately 1 min due to the high ratio of the chiral Raman signal relative to the achiral CARS background. Here, we present the first demonstration of heterodyne‐detected CARS‐ROA of chiral molecules dissolved in an achiral solvent by using an experimental setup built from a conventional broadband CARS spectrometer. Specifically, the two atropisomers (R/S) of 2,2′‐Bis(methoxymethoxy)‐1,1′‐binaphthyl, a methoxymethyl (MOM) bis‐protected derivative of 1,1′‐Bi‐2‐naphthol (BINOL), dissolved in the achiral organic solvent dichloromethane (DCM) were characterized by employing ~1 ps, 1 mW of pump pulses and ~60 fs, 10 mW of Stokes pulses within approximately 4‐min acquisition time. MOM‐BINOL is an important precursor for the synthesis of a great variety of many chiral auxiliaries including binaphthyl phosphoric acids, which are an important class of chiral organocatalysts used in asymmetric reactions. Overall, this work is a first step toward kinetic reaction monitoring in organocatalysis by coherent ROA providing the necessary short acquisition times.

Highly Soluble Dimethoxymethyl Tetrathiafulvalene with Excellent Stability for Non-Aqueous Redox Flow Batteries.

Non-aqueous redox flow batteries (RFBs) are highly attractive for grid-scale energy storage applications because of their independent design of energy and power, high energy density and efficiency, easy maintenance, and potentially low cost. In order to develop active molecules with large solubility, excellent electrochemical stability, and high redox potential for a non-aqueous RFB catholyte, herein, two flexible methoxymethyl groups had been attached to a famous redox-active tetrathiafulvalene (TTF) core. The strong intermolecular packing of the rigid TTF unit was effectively depressed, leading to a dramatically improved solubility of up to 3.1 M in conventional carbonate solvents. The performance of the obtained dimethoxymethyl TTF (DMM-TTF) was studied in a semi-solid RFB system with Li foil as the counter electrode. When using porous Celgard as the separator, the hybrid RFB with 0.1 M DMM-TTF had two high discharge plateaus at 3.20 and 3.52 V and a low capacity retention of 30.7% after 100 cycles at 5 mA cm-2. Replacing Celgard with a permselective membrane, the capacity retention was increased to 85.4%. Further increasing the concentration of DMM-TTF to 1.0 M and current density to 20 mA cm-2, the hybrid RFB exhibited a high volumetric discharge capacity of 48.5 A h L-1 and an energy density of 154 W h L-1. The capacity was maintained at 72.2% after 100 cycles (10.7 days). The great redox stability of DMM-TTF was revealed by UV-vis and 1H NMR tests and verified by density functional theory calculations. Therefore, the methoxymethyl group is an excellent group to increase the solubility while maintaining the redox capability of TTF for high-performance non-aqueous RFBs.

Observation of induction period and oxygenated intermediates in methane oxidation over Pt catalyst

Selective oxidation of methane is one of the most attractive routes for methane to chemicals. However, mechanistic understanding and avoiding over-oxidation have great challenges because of its very rapid reaction rate. Herein, a capillary micro-reaction system was introduced to monitor the initial stage of methane oxidation over platinum. For the first time, an induction period is observed, during which oxygenated intermediates, such as methanol, acetone, methyl methoxy acetate, etc., are detected. Induction period can be shortened by methane pretreatment at 600°C, which generates highly active species containing unsaturated bonds. Combined these findings and observations of in situ characterizations, the evolution route of methane oxidation over Pt is prosed, i.e., the reaction starts from the formation of initial species containing Pt-C bond, followed by the generation of oxygenated intermediates, and ended with the over-oxidation of the intermediates to CO/CO2.

Synthesis of PDMS/PEG graft-like and block copolymers via industrially relevant reverse iodine transfer polymerization

Advanced polymer structures are gaining traction in the coatings industry where they may, for instance, give rise to antifouling and anti-icing surfaces. With a focus on industrial feasibility, a series of copolymers from poly(dimethylsiloxane) monomethacrylate (PDMSMA), methoxy poly(ethylene glycol) monomethacrylate (MPEGMA) and methyl methacrylate (MMA) were prepared via reverse iodine transfer polymerization (RITP) and reversible complexation mediated polymerization (RCMP). Using inexpensive materials and synthesis approaches scalable for larger industrial quantities, a variety of (amphiphilic) copolymers and block copolymers were prepared. Compared to semi-batch free-radical polymerization (FRP), the RITP/RCMP approaches resulted in higher conversions of the macromonomers, lower polymer dispersities, allowed synthesis of block copolymers, as well as being simpler than most other common RDRP techniques.

Efficient organic solar cells by modulating photoactive layer morphology with halogen-free additives

Optimizing the morphology of the photoactive layer by additives strategy is one of the successful methods for increasing efficiency in organic solar cells (OSCs). In this work, a halogen-free solvent additive, methoxy methyl phenyl sulfide (MMPS) added to the PTB7-Th:PC71BM-based system to improve the optoelectronic property for OSCs by modulating the phase separation and crystallinity in the photoactive layer. It is found that the addition of MMPS could well modulate the aggregation and diffusion of donor and acceptor to form an excellent bicontinuous interpenetrating network, which improved exciton dissociation enhanced charge transport and significantly inhibited charge recombination. Consequently, the PCE of device based on the PTB7-Th:PC71BM blend with 3% MMPS is 9.24%, which is a 92.5% efficiency improvement compared to the device without additives. These results indicate that our work effectively optimizes the performance parameters of devices, providing new ideas for the preparation of OSCs on a large scale and industrialization.

β-(Z)-Selective alkyne hydrosilylation by a N,O-functionalized NHC-based rhodium(I) catalyst.

Neutral and cationic cyclooctadiene rhodium(I) complexes with a lutidine-derived polydentate ligand having NHC and methoxy side-donor functions, [RhBr(cod)(κC-tBuImCH2PyCH2OMe)] and [Rh(cod)(κ2C,N-tBuImCH2PyCH2OMe)]PF6, have been prepared. Carbonylation of the cationic compound yields the dicarbonyl complex [Rh(CO)2(κ2C,N-tBuImCH2PyCH2OMe)]PF6 whereas carbonylation of the neutral compound affords a mixture of di- and monocarbonyl neutral complexes [RhBr(CO)2(κC-tBuImCH2PyCH2OMe)] and [RhBr(CO)(κ2C,N-tBuImCH2PyCH2OMe)]. These complexes efficiently catalyze the hydrosilylation of 1-hexyne with HSiMe2Ph with a marked selectivity towards the β-(Z)-vinylsilane product. Catalyst [RhBr(CO)(κ2C,N-tBuImCH2PyCH2OMe)] showed a superior catalytic performance, in terms of both activity and selectivity, and has been applied to the hydrosilylation of a range of 1-alkynes and phenylacetylene derivatives with diverse hydrosilanes, including HSiMe2Ph, HSiMePh2, HSiPh3 and HSiEt3, showing excellent β-(Z) selectivity for the hydrosilylation of linear aliphatic 1-alkynes. Hydrosilylation of internal alkynes, such as diphenylacetylene and 1-phenyl-1-propyne, selectively affords the syn-addition vinylsilane products. The β-(Z) selectivity of these catalysts contrasts with that of related rhodium(I) catalysts based on 2-picolyl-functionalised NHC ligands, which were reported to be β-(E) selective. An energy barrier ΔG‡ of 19.8 ± 2.0 kcal mol-1 (298 K) has been determined from kinetic studies on the hydrosilylation of 1-hexyne with HSiMe2Ph. DFT studies suggest that the methoxy-methyl group is unlikely to be involved in the activation of hydrosilane, and then hydrosilane activation is likely to proceed via a classical Si-H oxidative addition.

Synthesis of Unsymmetrical Ketones Using Chelation-Controlled Sequential Substitution of N-Triazinylamide/Weinreb Amide by Organometallic Reagents.

N-(2,4-Dimethoxy-1,3,5-triazinyl)amide was found to exhibit similar behavior to N-methoxy-N-methylamide (Weinreb amide) but higher reactivity for nucleophilic substitution by organometallic reagents. Triazinylamide suppresses overaddition, leading to the formation of a tertiary alcohol by the chelating ability of the triazinyl and carbonyl groups. Ureas possessing both triazinylamino and methoxy(methyl)amino groups underwent sequential nucleophilic substitution with different organometallic reagents, which furnished unsymmetrical ketones without any detectable tertiary alcohols.

Synthesis, Characterization, Hirshfeld Surface Analysis, Crystal Structure and Molecular Modeling Studies of 1-(4-(Methoxy(phenyl)methyl)-2-methylphenoxy)butan-2-one Derivative as a Novel α-Glucosidase Inhibitor

The crystal compound was synthesized and characterized using conventional analytical techniques. The compound C19H21O3 crystallizes in a monoclinic crystal system with the space group P21/c. The crystal structure is stabilized by C-H…O interactions. The structure is further reinforced by π-π interactions. During in vitro inhibition of α-glucosidase, the crystal compound exhibited a significant inhibition of the enzyme (IC50: 10.30 ± 0.25 µg/mL) in comparison with the control, acarbose (IC50: 12.00 ± 0.10 µg/mL). Molecular docking studies were carried out for the crystal compound with the α-glucosidase protein model, which demonstrated that the crystal molecule has a good binding affinity (−10.8 kcal/mol) compared with that of acarbose (−8.2 kcal/mol). The molecular dynamics simulations and binding free energy calculations depicted the stability of the crystal molecule throughout the simulation period (100 ns). Further, a Hirshfeld analysis was carried out in order to understand the packing pattern and intermolecular interactions. The energy difference between the frontier molecular orbitals (FMO) was 4.95 eV.

A Convenient Synthesis towards 2-Bromo-2-(methoxy(phenyl)methyl)malononitrile and 2-Iodo-2-(methoxy(phenyl)methyl)malononitrile

This short note elaborates a concise protocol for the synthesis of two novel vicinal haloethers bearing a malonontrile group, 2-bromo-2-(methoxy(phenyl)methyl)malononitrile (1) and 2-iodo-2-(methoxy(phenyl)methyl)malononitrile (2). The structures of the synthesized compounds were confirmed by 1H, 13C-NMR spectroscopy. The final products indicate that methanol not only acts as solvent but also participates in and dominates the reaction result.

Superhydrophobic nanocomposite coatings based on different polysiloxane matrices designed for electrical insulators

The present paper describes for the first time the influence of three different kinds of polysiloxane as hydrophobic agent on superhydrophobic coatings for electrical insulators: a trimethoxy (2,2,4-trimethyl pentyl)-based silane; a mixture of methyl methoxy siloxane with methylsilsesquioxane; a mixture of dimethyl siloxane, methylsilsesquioxanes and n-octyl silsesquioxanes. The polysiloxane properties were investigated by thermogravimetric (TGA) and hydrophobic (contact and sliding angles) analysis, indicating great differences on thermal properties and surface free energy. The polysiloxane binders were loaded with different sizes of microsized alumina trihydrate (ATH) and organophilic nanosilica functionalized with octyl-silane and polydimethylsiloxane (PDMS). The hydrophobicity of the coating was evaluated by water contact angle (WCA) and sliding angle (SA). The morphology and roughness of the coatings were investigated by scanning electron microscopy (SEM) and atomic force microscopy (AFM). Moreover the superhydrophobic durability of the coatings was evaluated by water immersion, hydrophobicity recovery, hydrophobicity transfer and adhesion. The effectiveness of these materials as coatings for glass electrical insulator was evaluated by tracking and erosion resistance using the inclined plane test (IPT). The results showed that the polysiloxane based on a mixture of methyl methoxy siloxane with methylsilsesquioxanee loaded with ATH and PDMS-treated silica exhibited the most promising characteristics as high contact angle, self-cleaning ability, good adhesion to the substrate and low number of leakage current peaks during the tracking and erosion resistance test. Such characteristics can bring benefits on electrical insulators like reducing the formation of conductive surface paths and the consequent degradation of the coating by dry band arcs, increasing its resistance when exposed to the electric field.

Methyl Internal Rotation in Fruit Esters: Chain-Length Effect Observed in the Microwave Spectrum of Methyl Hexanoate.

The gas-phase structures of the fruit ester methyl hexanoate, CH3-O-(C=O)-C5H11, have been determined using a combination of molecular jet Fourier-transform microwave spectroscopy and quantum chemistry. The microwave spectrum was measured in the frequency range of 3 to 23 GHz. Two conformers were assigned, one with Cs symmetry and the other with C1 symmetry where the γ-carbon atom of the hexyl chain is in a gauche orientation in relation to the carbonyl bond. Splittings of all rotational lines into doublets were observed due to internal rotation of the methoxy methyl group CH3-O, from which torsional barriers of 417 cm−1 and 415 cm−1, respectively, could be deduced. Rotational constants obtained from geometry optimizations at various levels of theory were compared to the experimental values, confirming the soft degree of freedom of the (C=O)-C bond observed for the C1 conformer of shorter methyl alkynoates like methyl butyrate and methyl valerate. Comparison of the barriers to methyl internal rotation of methyl hexanoate to those of other CH3-O-(C=O)-R molecules leads to the conclusion that though the barrier height is relatively constant at about 420 cm−1, it decreases in molecules with longer R.

Electrochemical and gravimeter study on corrosion inhibition by (methoxymethyl) triphenylphosphonium chloride in acid media H2SO4 0.5M

In this work, we study the inhibitory efficacy of organometallic compounds (phosphonium salts) used as an inhibitor on the corrosion of carbon steel XC70. The compound is (methoxy methyl) triphenyl phosphonium chloride (MMTP Cl). The study was performed in a 0.5M H2SO4 media. The measurements were performed by three electrochemical methods: electrochemical impedance spectroscopy potentiodynamic polarization and gravimeter method. One of the most widely used methods of protecting metals against corrosion is the use of inhibitors. They act by adsorption on the metal surface. The effectiveness of the corrosion inhibitor has been evaluated by several methods; polarization technique (Tafel line); electrochemical impedance and mass loss spectroscopy (immersion test) in acidic media. The results have allowed us to deduce the steel corrosion rate as well as other electrochemical parameters. The overall results show that the compounds (MMTP Cl) was chemically adsorbed on the steel surface. And in this case, adsorption occurs on the surface of the metal, according to the Langmuir modelin 0.5M H2SO4 solution. And the best concentration that decreasing the corrosion rate and gives inhibitory efficacy is 1ppm (R = 74.19%). A Comparative electrochemical study with that reported in the literature revealed that the efficiency of the inhibitors follows the order: 1-butyl triphenyl phosphonium chloride> (chloromethyl) triphenyl phosphonium chloride (CTP)>tetraphenyl phosphonium chloride (TP)>triphenyl phosphine oxide (TPO) > triphenyl (phenyl methyl) phosphonium chloride (TPM). It was also reported in the literature that the efficiency of halide inhibitors follows the order: I-> Br->Cl->F-.

Preparation and Characterization of a Thermal Barrier Heat-Resistant Silicone Coating

In this study, a heat resistant coating with thermal barrier property was designed. Two types of silicone resin (based on methoxy methyl polysiloxane and methyl phenyl silicone resin) were used as thermal resistant binders, and the black iron oxide pigment and glass micro hollow sphere (MHS) additive were utilized to formulate the heat resistant/thermal barrier coatings. Coatings were applied to the steel substrates, and general properties of the coatings such as film formation, curing, and adhesion were then studied. The thermal stability of the coatings was evaluated by thermogravimetric analysis up to 450 °C. The thermal conductivity coefficient of the coatings was measured by temperature modulated differential scanning colorimeter (TMDSC). Investigation of the properties of all coatings showed that the silicone coating with the 7% of hollow microsphere had higher thermal stability (Tmaximum weight loss= 538 °C) and better barrier properties (Thermal conductivity= 0.29 W/mK (compared with other coatings.

Site-specific scaling relations observed during methanol-to-olefin conversion over ZSM-5 catalysts

The conversion of methanol over ZSM-5 catalysts was studied using step response and temperature-programmed desorption and surface reaction analyses in a temporal analysis of products reactor, as well as quasi-elastic neutron scattering and Fourier transform infrared investigations, buttressed by archived 13C magic angle spinning nuclear magnetic resonance studies. The results were combined with micro-kinetic models that simulated the formation of the first C–C bond and primary olefin(s) from methanol. Dimethyl ether was the major surface oxygenate and a source of surface methoxy species. Propylene, the major olefin produced from dimethyl ether, was formed with a reaction barrier of ∼ 200 kJ mol−1, in agreement with archived density functional theory calculations. Propylene could form from dimethyl ether via a methoxymethyl mechanism under intrinsic kinetic conditions. Site-specific scaling relations between the barriers to methyl propenyl ether and methoxy methyl species formation and dimethyl ether desorption were observed. The active sites of the ZSM-5 catalysts can be locally optimised and selectively tuned to improve their activity during the conversion of methanol to olefin(s).