Presence Of Acid Catalyst Research Articles

Efficient continuous synthesis of long-chain alkylbenzenes catalyzed by ionic liquids in microreaction systems

Alkylbenzene (LAB) is an important benzene derivative that can be used as a raw material for high-performance anionic surfactants such as alkylbenzene sulfonates (LAS) to meet the new requirements for surfactants in many fields. LAB can be synthesized through Friedel-Crafts reaction in the presence of acidic catalysts as alkylating agents, which is commonly used in the production of fine chemicals. In this work, a novel and efficient continuous flow micro reaction system was introduced to enhance the production of long-chain alkylbenzene catalyzed by [(CH3)3NH][Al2Cl7] ionic liquid. The optimal conditions were investigated for the synthesis of long-chain alkylbenzenes with the 1-tetradecene and mixing α-alkenes of C14-C16 from Fischer-Tropsch process. The results showed that the yield of benzene alkylation can achieve 99 % under the optimal process conditions which the reaction tube length was 2000 mm, the reaction temperature was 30 ℃, the catalyst dosage was 0.30 mL/min and the molar ratio of aluminum chloride to trimethylamine hydrochloride was 2:1. In addition, α-alkenes with C14-C16 lead to deactivation of the ionic liquids catalyst easier because of transfer of AlCl3 from the ionic liquid to the organic phase compared to the pure 1-tetradecene as an alkylating agent. Continuous synthesis of the long-chain alkylbenzenes catalyzed by ionic liquids can achieve in the microchannel reaction system by controlling the flow patterns.

Urethane Synthesis in the Presence of Organic Acid Catalysts-A Computational Study.

A general mechanism for catalytic urethane formation in the presence of acid catalysts, dimethyl hydrogen phosphate (DMHP), methanesulfonic acid (MSA), and trifluoromethanesulfonic acid (TFMSA), has been studied using theoretical methods. The reaction of phenyl isocyanate (PhNCO) and butan-1-ol (BuOH) has been selected to describe the energetic and structural features of the catalyst-free urethane formation. The catalytic activities of DMHP, MSA, and TFMSA have been compared by adding them to the PhNCO-BuOH model system. The thermodynamic properties of the reactions were computed by using the G3MP2BHandHLYP composite method. It was revealed that in the presence of trifluoromethanesulfonic acid, the activation energy was the lowest within the studied set of catalysts. The achieved results indicate that acids can be successfully employed in urethane synthesis and the mechanism was described.

STUDY OF ACID CATALYSTS IN THE GLYCEROL ETHERIFICATION WITH BENZYL ALCOHOL

Glycerol (Gly) is the major by-product of the biodiesel production (approximately 10 wt.%). There are different research focusing on developing glycerol utilization to produce value-added chemicals. One of them is the etherification with alcohols in the presence of acidic catalysts. In the present work, the catalytic behaviour of SiO2-based system functionalized with heteropolyacids (HPA: H3O40PW12.xH2O) was studied in the etherification of Gly with benzyl alcohol (BA). The solids were impregnated with different solutions of a HPA (28, 35 and 40%) and characterized. Very good catalytic performance was achieved (94% conversion and 78% of selectivity to ME1: 3-benzyloxy-1, 2-propanediol) after 360 min of reaction, at 120°C and Gly: BA= 3:1, with 10 wt.% of SiO2-HPA35. This system was compared with functionalized carbon-based catalysts (Cst-SO3H and Ccs-SO3H) and it was observed that the results were similar, conversion over 90% and selectivity between 70 -80% to some of the desired products (ME1).

Determination of clobetasol propionate in cosmetics by high performance liquid chromatography with pre-column fluorescence derivatization of 4-hydrazino-7-nitrobenzo [C] [1,2,5] oxadiazole

In this study, a fluorescent labeling reagent 4-hydrazino-7-nitrobenzo [c] [1,2,5] oxadiazole (NBD-NHNH2) was synthesized and used for fluorescence detection of clobetasol propionate in cosmetics by high performance liquid chromatography. In the presence of acidic catalyst (pH = 6.0), NBD-NHNH2 reacted at 45 °C for 30 min, and clobetasol propionate can be labeled quickly and efficiently. These derivatives have excellent stability and fluorescent properties. The maximum excitation wavelength was 450 nm, and the emission wavelength was 550 nm. The four cosmetic formulations were completely separated on a Waters e2695 HPLC C18 column by gradient elution. Under the optimal conditions, the standard curve showed a good linear response, and the correlation coefficient of r 2 = 0.9999. The LOD and LOQ were 0.01 ng/mL and 0.03 ng/mL, respectively. Therefore, NBD-NHNH2 was successfully applied in the detection of clobetasol propionate illegal added in cosmetics.

Synthesis and Pharmacological Evaluation of Promising Coumarin Methyl Ester/ Di/Tri/Tetra Peptide Derivatives

Coumarin is a phenol, consisting of benzene ring and alpha-pyrone ring. Coumarins are prepared through Pechmann reaction, which involve condensation of phenol with ethyl acetoacetate in the presence of acid catalyst. Coumarins are being used widely due to their various biological activities in recent years, like anticoagulant, antibacterial, antitumoral, antitubercular, antifungal, MAO inhibitor activity, antioxidant, anti-inflammatory and as CNS active compounds. Methyl esters of amino acids and their di/tri and tetrapeptides derivatives were prepared using coupling agent DCC and a base NMM by stirring continuously for 36 hours. The compounds prepared were analyzed and the structures are elucidated by TLC, IR and 1H NMR spectral data. They were screened for antibacterial activity against three bacterial species and antifungal activity against one species

1-Aminoalkylphosphonium Derivatives: Smart Synthetic Equivalents of N-Acyliminium-Type Cations, and Maybe Something More: A Review.

N-acyliminium-type cations are examples of highly reactive intermediates that are willingly used in organic synthesis in intra- or intermolecular α-amidoalkylation reactions. They are usually generated in situ from their corresponding precursors in the presence of acidic catalysts (Brønsted or Lewis acids). In this context, 1-aminoalkyltriarylphosphonium derivatives deserve particular attention. The positively charged phosphonium moiety located in the immediate vicinity of the N-acyl group significantly facilitates Cα-P+ bond breaking, even without the use of catalyst. Moreover, minor structural modifications of 1-aminoalkyltriarylphosphonium derivatives make it possible to modulate their reactivity in a simple way. Therefore, these types of compounds can be considered as smart synthetic equivalents of N-acyliminium-type cations. This review intends to familiarize a wide audience with the unique properties of 1-aminoalkyltriarylphosphonium derivatives and encourage their wider use in organic synthesis. Hence, the most important methods for the preparation of 1-aminoalkyltriarylphosphonium salts, as well as the area of their potential synthetic utilization, are demonstrated. In particular, the structure–reactivity correlations for the phosphonium salts are discussed. It was shown that 1-aminoalkyltriarylphosphonium salts are not only an interesting alternative to other α-amidoalkylating agents but also can be used in such important transformations as the Wittig reaction or heterocyclizations. Finally, the prospects and limitations of their further applications in synthesis and medicinal chemistry were considered.

An Eco-Friendly Terpolymer Resin: Synthesis, Characterization and Ion‐Exchange Properties

2, 2’- Biphenol-Hexamethylenediamine-formaldehyde Terpolymers (BPHDF) were synthesized by the condensation of 2, 2’- Biphenol, Hexamethylenediamine, and formaldehyde in the presence of acid catalyst with varying molar ratios of reacting monomers. Terpolymer composition has been determined on the basis of their elemental analysis and the number–average molecular weight of these resins was determined by conductometric titration in nonaqueous medium. The viscosity measurements were carried out in N, N-dimethyl formamide which indicate normal behaviour. IR spectra were studied to elucidate the structure. The terpolymer resin has been further characterized by UV–visible and 1H-NMR spectra. The surface morphology of the terpolymer resin was examined by scanning electron microscopy. One of the important applications of these terpolymers is their capability to act as chelating ion-exchangers. The newly synthesized terpolymers proved to be selective for chelating ion-exchange properties and showed a powerful adsorption towards specific metal ions like Co2+, Hg2+, Cd2+, Pb2+. A batch equilibration method was adopted to study the selectivity of the metal ion uptake involving the measurement of the distribution of the given metal ion between the polymer sample and a solution containing the metal ion over a wide range of concentrations and pHs of different electrolytes. The terpolymers showed a higher selectivity for Co2+> Hg2+> Cd2+> Pb2+.It is also observed that the amount of metal ions absorption by the BPHDF terpolymer resins increases in the order: BPHDF-3 > BPHDF-2 > BPHDF-1 due to introduction of more and more phenolic groups in terpolymer resins from BPHDF-1 to BPHDF-3.

Stability of phenolic antioxidants in the presence of sulfonic acid: Model compound studies for moisture-crosslinked polyethylene

Alkoxysilane-functionalized polyethylene can be crosslinked in the presence of acid catalysts, including Brønsted acids, to yield durable pipe and cable insulation materials. However, Brønsted acids can also react with additives present in the formulation such as phenolic antioxidants, resulting in reduced additive efficacy and undesired reaction products. To provide guidelines for the selection of stable phenolic antioxidants in the presence of Brønsted acids, reactions of 4 model alkylphenol compounds in the presence of p-dodecylbenzenesulfonic acid (DBSA) in dodecane were studied as a solution model for polyethylene-based systems. The results point to increasing stability towards DBSA of phenolic compounds when: (i) alkyl groups have less substitution (tertiary carbon compared to quaternary carbon), (ii) they have alkyl-substitution in the para position, and (iii) they have a reduced number of alkyl substituents around the phenol ring. To confirm the trends observed with the model compounds, commercially available antioxidants were also evaluated under the same conditions. Antioxidants with alkyl or isocyanurate bridges had reaction rates comparable to butylated hydroxytoluene (BHT) and followed the trend outlined in model alkylphenols with regards to alkyl group substitution. By comparison, the sulfur-bridged antioxidant stood out as rapidly consumed under the reaction conditions. Therefore, selection of phenolic antioxidants for formulations containing strong Brønsted acids should generally favor phenolic compounds with alkyl-substituted para positions and limited number of alkyl substituents in non-para positions, and without quaternary carbon substituents. Moreover, stability of alternate sulfur-containing antioxidants should be assessed if used with sulfonic acids, given the rapid decomposition of the sulfur-bridged antioxidant observed in this work.

Synthesis of 3,3′- Di-indolylmethanes under mild conditions by Microwave Irradiation Mediated Reactions of Indoles with C, N-Diaryl nitrones

3,3′-Di-indolylmethane derivatives are important biologically active compounds possessing anti-cancer properties. Hence, development of synthetic routes to these are of great interest to organic chemists. In the present communication we report a high-yield method using mild reaction conditions and short reaction times for the synthesis of 3,3′-di-indolylmethane derivatives. The method involved reactions of indole and substituted indoles with C,N-disubstituted nitrones in the presence of acid catalysts, with the utilisation of microwave irradiation techniques. Reactions of indole, 2-methyl indole and 2-phenyl indole were performed with ten different C,N-diaryl- and C-aryl-N-methyl- nitrones in dichloromethane solution in the absence and presence of acid catalysts, viz. ytterbium triflate, p-toluene sulphonic acid and Montmorillonite clay K-10. Reaction times varied between 2 to 18 minutes. In general, yields of the catalysed reactions were above 75%. The products were characterised spectroscopically, including two-dimensional NMR studies. The microwave irradiation technique enhanced reaction rates by a significant amount. Ytterbium triflate proved to be the best catalyst, giving clean reactions, without formation of by-products, in high yields. The structure and conformation of 3,3′-di-indolyl-phenylmethane were computed. GRAPHICAL ABSTRACT: We report a high-yield method using mild reaction conditions and short reaction times for the synthesis of 3,3′-di-indolylmethane derivatives, involving reactions of indole and substituted indoles with C, N-disubstituted nitrones in the presence of acid catalysts using microwave irradiation.

Cyclocondensation of o‐Phenylenediamines with 2‐Oxo‐ethanimidothioates: A Novel Synthesis of 2‐Amino‐3‐(het)aryl‐quinoxalines

Abstract2‐Amino‐3‐(het)aryl‐quinoxalines were synthesized by the cyclization reaction between 2‐oxo‐ethanimidothioates and o‐phenylenediamine in the presence of acid catalyst p‐TSA in toluene at 80 °C. The products were obtained in 58–84 % yields. The required substrates 2‐oxo‐ethanimidothioates were synthesized by the condensation reaction between α‐oxodithioester and amine in the presence of sodium hydride in DMF followed treatment with methyl iodide.

Effect of acid catalysts on hydrothermal carbonization of Malaysian oil palm residues (leaves, fronds, and shells) for hydrochar production

Malaysian oil palm industry produces a significant amount of oil palm residue as solid wastes. These solid wastes are comprised of oil palm residue which contains the stem, fronds from the farms, empty fruit bunch (EFB), mesocarp fibre (MF), and palm kernel shell (PKS) from the oil palm–processing factories. These residues are not successfully reused for other purposes, and the current dumping methods can possibly trigger unfavourable effects to the environment. As oil palm residues are a readily available waste biomass, it has a high potential to be converted into valuable energy-derived products. Hydrothermal carbonization (HTC), which is a thermochemical process, is a method used to treat biomass to produce hydrochar under hot-compressed water. Oil palm residues (palm leaves, palm fronds, and palm shell) were used as the feedstock for producing carbonaceous hydrochar. The key objective of this study is to examine the effect of the reaction temperature, residence time, and acid catalysts on the HTC process. HTC of oil palm residues was optimized at different operating temperatures from 140 to 300 °C and different reaction times between 30 and 240 minutes with a biomass-to-water ratio of 1:10 wt%. Acid catalysts such as citric acid and ascorbic acid were used for the HTC process. The hydrochar produced is further characterized using heating value and elemental and Fourier transform infrared (FTIR) analysis. The yield of hydrochar reduces with the rise of temperature and time but it increases in the presence of acid catalysts. The carbon content of hydrochar is observed to be between 44.36 and 49.50%. The FTIR analysis showed that a high intensity at 1423 cm−1 indicates a high content of lignin and cellulose in the hydrochar. A considerable decrease in the H/C and O/C atomic ratio shows that the dehydration and decarboxylation take place during the HTC process.

Simulation and optimization of Camelina oil fatty acids reaction to produce fatty acid methyl esters in a reactive distillation reactor

Reactive distillation (RD) is a chemical unit operation in which chemical reaction and product separation occurs simultaneously in one unit resulted in reduce the number of downstream steps, energy savings, and greenhouse gases. In the current work, process flow sheets for industrial routes for conversion of camelina oil fatty acids to fatty acid methyl esters (biodiesel) in presence of acid catalyst is modelled in Aspen HYSYS for the purpose to scale up the esters production. The effect of the operating and design parameters is optimized in addition to design the production plant. The simulation results showed that optimum ester yield is obtained for linoleic acid and palmatic components using 6:1 alcohol to oil ratio, reaction temperature 60°C and feeding the oil and the alcohol at stage number 3 and 5 respectively.

Kinetic study for oligomerization of acetaldehyde over cation exchange resin

Several industrially important liquid phase reactions which involve acetaldehyde as the main reactant are practised in the presence of acidic catalyst. However, under these conditions, acetaldehyde also undergoes oligomerization via self-aldol condensation reactions to form multiple side products thereby reducing the selectivity of the desired product. In this work, we investigate the detailed kinetics of oligomerization over a commonly used commercial cation exchange resin, Amberlyst-15 as catalyst. It is found that, crotonaldehyde and subsequent heavy aldols are formed in the reaction. Molecular weight distribution of the oligomers formed during the reaction is verified with Flory’s statistical method. Kinetic studies are performed in an autoclave over a temperature range of 343−363 K. The effect of different parameters such as temperature, concentration, catalyst loading, and catalyst reusability is examined. A kinetic model based on Langmuir-Hinshelwood-Hougen-Watson (LHHW) rate expression is proposed to explain acetaldehyde oligomerization in the presence of acidic resin.

Исследование процесса получения и подготовки к использованию экологически чистого биотоплива на основе таллового масла

The article discusses the scientific and technical issues of the methodology for producing liquid biofuel from renewable raw materials of plant origin. As raw materials used wastes from the production of pulp and paper mills — tall oil. The purpose of the work was to study the process of obtaining and determining ways to use the product. The optimal conditions for obtaining biodiesel are determined. The processing of raw materials was carried out by heating it with methanol in a ratio of 1:0,3 at a temperature of 50–65 °C for 2 hours in the presence of 2 % catalyst. The product, after separation of the resulting intermediate, was finally washed with water from the catalyst residues. The process was controlled spectrophotometrically. Using gas-liquid chromatography with mass spectrometric detection, the complete chemical composition of the used raw materials of various degrees of purification was established. It is shown that the main content in the processed oil is represented by natural lipids. Their fatty acid composition is described, comprising more than thirty C10–C24 fatty acids. A general scheme for producing biodiesel, which is a mixture of fatty acid alkyl esters, has been developed. The product was obtained by chemical transformation in the presence of acid catalysts, followed by the formation of fatty acid methyl esters. The component composition of the obtained product, biodiesel, was studied and it was shown that it consists of a mixture of methyl esters of fatty acids more than 95 %. In biodiesel, more than two hundred organic substances are also contained in the form of an insignificant amount of microimpurities. Their number fluctuated around 0,001 %. The basic physico-chemical characteristics of the obtained biodiesel are described in comparison with international requirements for biofuels. The analyzed product samples obtained from distilled TM, according to mass spectrometry, did not contain harmful impurities bromine, iodine, phosphorus and sulfur-substituted compounds. The total content of chlorine-substituted organic substances in all samples did not exceed 0,07 ± 0,02 %, and N-substituted derivatives did not exceed 0,05 ± 0,01 %, which indicates a rather high ecological purity of bitumen fuel. The main directions of the possible use of the product as liquid fuel for mini-boiler nozzles, as well as for operation in conventional diesel engines, are determined.

Catalytic Alkylation of Adamantane with Propylene: Quantum-Chemical Calculations and Experimental Data

The mechanism of interaction of adamantane with propylene has been studied by quantum-chemical calculations within the density functional theory (DFT). It has been shown that the main products of adamantane alkylation with propylene in the presence of acid catalysts are hydrocarbons with unbranched (normal-chain) substituents, 1-n-propyl- and 1-n-propenyladamantanes. The main stages of adamantane alkylation and the geometric and electronic structures of the intermediates have been determined. The thermodynamic characteristics of the studied adamantanes have been found, and the mechanisms of individual steps of their transformations have been proposed. The obtained data make it possible to control the process of preparation of substituted adamantanes with a defined structure that are of interest for the development of efficient energy-rich materials, high-density fuels, and thermally stable polymers.

ACID-CATALYZED REARRANGEMENT OF 1-ACYL-2-AZABUTA-1,3-DIENES TO 4-PYRROLIN-2-ONES

1-Acyl-2-azabuta-1,3-dienes underwent rearrangement to 4-pyrrolin-2-ones in the presence of acidic catalysts (silica gel or ZnCl 2 ) and water. The reaction proceeded via the formation of 2,3-dihydroxy-3,4-dihydropyrrole and 2-hydroxy-2 Н -pyrrole intermediates, the latter of which was transformed by [1,5]-sigmatropic shift of carbonyl substituent and prototropic isomerization. 4-Chloro-substituted 1-acetyl-2-azabuta-1,3-dienes were stable toward rearrangement, while brominated analogs rearranged into 4-pyrrolin-2-ones, probably as a result of the initial radical hydrodebromination. According to calculations performed at the DFT level, two steps of the reaction were catalyzed by acid: the cyclization of 2-azabutadiene and the sigmatropic shift in the 2-hydroxy-2 Н -pyrrole intermediate. Authors: Nikolai V. Rostovskii, Ilia A. Smetanin, Alexander N. Koronatov, Anastasiya V. Agafonova, Vasilii V. Potapenkov, Alexander F. Khlebnikov, Mikhail S. Novikov*

A review on electrophilic thiocyanation of aromatic and heteroaromatic compounds

The electrophilic thiocyanation of aromatic and heteroaromatic compounds such as oxindoles, indoles, isatins, indolines, quinolines, and pyrroles and also N-activeted arenes such as anilines, N,N-dialkylamines, and arylamines with thiocyanation agent/oxidant in the presence of acidic catalyst are represents an essential direct procedure to the synthesis of aryl and heteroaryl thiocyanates derivatives. Various thiocyanation agents such as NH4SCN, KSCN and some catalysts especially ILs with thiocyanation agent are an important reagent for the production of such class of thiocyanate intermediates. In the decade past, the considerable advances have been made for the direct thiocyanation of aromatic, heteroaromatic and N-activeted arenes compounds with high selectivity and yield. In this review, we have classified a variety of procedures the last nine years based on various catalysts for the preparation of aryl and heteroaryl thiocyanates derivatives since 2012 until now.

Modeling and optimization of biodiesel production from microalgae in a batch reactor

In this research, biodiesel production from two types microalgae including Enteromorphacompressa, and Scenedesmus in the presence of acid catalyst and methanol in batch reactors was modeled. In this study, the reaction rate constants have been considered as different functions of both temperatures and catalyst concentrations to evaluate and compare the effect of these reaction rate constants on biodiesel production yield. Then the models were used to find the optimal conditions in order to maximize the biodiesel yield. In this regard, the kinetic parameters of models were calculated by using experimental data. Then, the effect of temperature, catalyst concentration, and methanol to oil ratio on the biodiesel yield were calculated. According to results, the models can accurately predict the effect of temperature, catalyst concentration, and methanol to oil ratio on the biodiesel yield. According to the results, there are direct relationship between biodiesel yield and the effective parameters. Results showed that the efficiency of biodiesel production more than 99% can be achieved at optimal condition.

Acid-catalyzed rearrangement of 1-acyl-2-azabuta-1,3-dienes to 4-pyrrolin-2-ones

1-Acyl-2-azabuta-1,3-dienes underwent rearrangement to 4-pyrrolin-2-ones in the presence of acidic catalysts (silica gel or ZnCl2) and water. The reaction proceeded via the formation of 2,3-dihydroxy-3,4-dihydropyrrole and 2-hydroxy-2Н-pyrrole intermediates, the latter of which was transformed by [1,5]-sigmatropic shift of carbonyl substituent and prototropic isomerization. 4-Chloro-substituted 1-acetyl-2-azabuta-1,3-dienes were stable toward rearrangement, while brominated analogs rearranged into 4-pyrrolin-2-ones, probably as a result of the initial radical hydrodebromination. According to calculations performed at the DFT level, two steps of the reaction were catalyzed by acid: the cyclization of 2-azabutadiene and the sigmatropic shift in the 2-hydroxy-2Н-pyrrole intermediate.

Metal-based Lewis acid catalysts for conversion of a variety of aldehydes with acetic anhydride to gem 1,1-diacetates

Selective protection of carbonyl groups such as oxathioacetals, acylals, acetals and dithioacetals is the vital steps in organic chemistry. Among these groups, protection of aldehydes such as diacetates (acylals) has attracted more attention in the organic chemistry due to its superior applications such as commodity chemical in various fields of chemistry, their ease of preparation and their stability toward basic and neutral conditions. Beyond their protecting role, 1,1-diacetates are important precursors for the synthesis of acetoxydienes, starting materials as valuable intermediates for Diels–Alder cycloaddition reactions and neutral and basic media. Also acylals have been used as intermediates in industry as cross-linking agents for cellulose in cotton. Protection of carbonyl group of aldehydes by acetic anhydride in the presence of acid catalyst is the most convenient way. This review precises chemoselective procedure for the preparation of acylals by using the metal-based Lewis acid catalysts, magnetic nanocatalysts, ionic liquids, strong protic acid and solid acids.