Catalyze Transfer Reactions Research Articles

Aminotransferase Class I and II Gene Family in the Jinjiang Oyster (Crassostrea ariakensis): Genomewide Identification, Phylogenetic Analysis and Expression Profiles after Salinity Stress

Aminotransferases are enzymes found in living organisms that catalyze transfer reactions between amino acids and keto acids, crucial for amino acid metabolism and synthesis. Aminotransferase classes I and II play a vital role in regulating osmolarity, protecting cells, and improving metabolic homeostasis and cellular fitness. To investigate the characteristics of the aminotransferase class I and II gene family and their roles in osmotic pressure regulation in the Jinjiang oyster (Crassostrea ariakensis), the gene structure, chromosomal localization, and phylogeny were characterized and the genes’ expression in the gill under high-salt stress was analyzed. In this study, eighteen Aminotransferase class I and II genes, including SPTLCa and SPTLCb, SPTa and SPTb, ALAT2a and ALAT2b, KAT3a and KAT3b, and ASTa, ASTb and ASTc, were identified. The physicochemical properties of 11 family members were stable, with their instability factors less than 40. Subcellular localization prediction showed that aminotransferase classes I and II were localized in the cytoplasm or mitochondria. Chromosomal localization results showed that the 18 aminotransferase class I and II genes were located on eight chromosomes. All members of this gene family had the Aminotran_1_2 structural domain which is associated with osmotic pressure regulation by adjusting the conversion reaction between amino acids and keto acids. Most gene expressions showed an initial increase followed by a decrease from 0 h to 12 h when the oysters were challenged by acute stress using artificial seawater with a salinity of 40. However, the expression of CarAGT2 and CarKAT3b genes showed an increased trend with increasing stress time. This study systematically investigated the bioinformatics characteristics of the aminotransferase class I and II gene family in C. ariakensis and their role in osmotic pressure regulation, which provides scientific data for understanding the potential functions of these genes in physiological adaptation, thereby expanding the research on osmoregulation in bivalves.

Interfacial Processes—The Key Steps of Phase Transfer Catalyzed Reactions

After short historical introduction, interfacial mechanism of phase transfer catalyzed (PTC) reactions of organic anions, induced by aqueous NaOH or KOH in two-phase systems is formulated. Subsequently experimental evidence that supports the interfacial deprotonation as the key initial step of these reactions is presented.

Design and Development of Novel Continuous Flow Stirred Multiphase Reactor: Liquid–Liquid–Liquid Phase Transfer Catalysed Synthesis of Guaiacol Glycidyl Ether

Phase transfer catalysed (PTC) reactions are used in several pharmaceutical and fine chemical industrial processes. We have developed a novel stirred tank reactor (Yadav reactor) to conduct batch and continuous liquid–liquid–liquid (L-L-L) PTC reactions. The reactor had a provision of using three independent stirrers for each phase, thereby having complete control over the rate of mass transfer across the two interfaces. In the continuous mode of operation, the top and bottom phases were continuously fed into the reactor while the middle phase was used as a batch. All three stirrers were used independently, thereby having independent control of mass transfer resistances. The reactor in a batch mode showed higher conversion and selectivity compared to a conventional batch reactor. L-L-L PTC reaction in the continuous mode was successfully performed without loss of the middle catalyst phase and with steady conversion and selectivity. The reaction of guaiacol with epichlorohydrin was conducted as a model reaction, with a 76% conversion of epichlorohydrin, 85% selectivity of guaiacol glycidyl ether, and the middle catalyst phase was stable throughout the process.

Experimental validation of equilibrium based mathematical modelling of liquid‐liquid phase transfer catalysis

The reaction between two compounds which reside in immiscible phases can be accelerated using a phase transfer catalyst. The catalyst helps to transfer a species ion from one phase to the other phase, thus promoting its reaction. Several mechanisms have been proposed to describe phase transfer catalyzed reactions. In this work, we have carried out an experimental and theoretical study of phase transfer catalysis in batch mode. A mathematical model is developed which helps to predict the progress of the reaction under different operating conditions. Here the different species in the aqueous phase are assumed to be in equilibrium and these react with the species in the organic phase. The effect of diffusional resistance inside the dispersed organic phase is shown to be negligible. The two reaction systems studied are the phase transfer catalyzed (i) thioetherification and (ii) benzyl alcohol oxidation using sodium hypochlorite. Batch experiments were performed to determine the effect of catalyst loading, solvent dilution, and pH. The experimental results show that with an increase in catalyst loading, the phase transfer catalyzed reactions were accelerated. The use of a minimal amount of solvent results in a better performance. Benzyl alcohol oxidation is favoured under low pH conditions. The developed model is able to capture the performance of the system over a wide range of operating conditions accurately.

Crosslinked polysulfone obtained by Wittig-Horner reaction in biphase system

Phase transfer catalyzed reactions are often more easily and cheaply performed than conventional method and they are therefore of particular interest. A polysulfone functionalized with phosphonate (2-PSF) was prepared under phase transfer catalysis (PTC) conditions, and it was evaluated by spectrometric method (Fourier transform infrared spectroscopy, using potassium bromide (KBr) pellet). The phosphorus content of the modified polysulfone was determined, and it was used for the determination the fraction of repeating units functionalized with phosphonate groups. The modified polysulfone contains 1.40 mmol phosphonate/g polysulfone. Polysulfone functionalized with phosphonate groups and polysulfone functionalized with aldehyde groups (3-PSF) were used in Wittig-Horner reaction, to introduce double bonds on polymer and to obtain crosslinked polysulfone (4-PSF). The reactions were performed using PTC method, solid-liquid (potassium carbonate (K2CO3), tetrahydrofuran (THF), tetraethylammonium iodide (TEAI)) system. The structure of polysulfone functionalized with phosphonate groups and polysulfone functionalized with aldehyde group were confirmed by 1H-, 13C-, and 31P-nuclear magnetic resonance (NMR). The peak for phosphorus in PSF-phosphonate appears in 31P NMR spectrum as a singlet at 25.712 ppm. The thermal properties of aldehyde, phosphonate, and crosslinked polysulfone were studied by thermogravimetric analysis (TG) and differential thermogravimetric analysis (DTG). Scanning electron microscopy images for polysulfone functionalized with phosphonate and crosslinked polysulfone are in concordance with nitrogen (N2) adsorption-desorption isotherms.POLYM. ENG. SCI., 2012. © 2011 Society of Plastics Engineers

A Systematic Investigation of Quaternary Ammonium Ions as Asymmetric Phase-Transfer Catalysts. Application of Quantitative Structure Activity/Selectivity Relationships

Although the synthetic utility of asymmetric phase-transfer catalysis continues to expand, the number of proven catalyst types and design criteria remains limited. At the origin of this scarcity is a lack in understanding of how catalyst structural features affect the rate and enantioselectivity of phase transfer catalyzed reactions. Described in this paper is the development of quantitative structure-activity relationships (QSAR) and -selectivity relationships (QSSR) for the alkylation of a protected glycine imine with libraries of quaternary ammonium ion catalysts. Catalyst descriptors including ammonium ion accessibility, interfacial adsorption affinity, and partition coefficient were found to correlate meaningfully with catalyst activity. The physical nature of the descriptors was rationalized through differing contributions of the interfacial and extraction mechanisms to the reaction under study. The variation in the observed enantioselectivity was rationalized employing a comparative molecular field analysis (CoMFA) using both the steric and electrostatic fields of the catalysts. A qualitative analysis of the developed model reveals preferred regions for catalyst binding to afford both configurations of the alkylated product.

Use of Diethoxymethane as a Solvent for Phase Transfer-CatalyzedO-Alkylation of Phenols

The effectiveness of diethoxymethane (DEM) as a solvent for O-alkylation of a variety of phenols under phase transfer conditions has been examined and evaluated. The reaction between 4-methoxy phenol and benzyl chloride was selected to compare reaction rates in various solvents and the efficiency of various PTCs. This reaction was further studied to develop a commercially amenable process complete with recycle streams and efficient product isolation. DEM is a good solvent for these types of phase transfer-catalyzed reactions and can be considered as an alternative solvent for dichloromethane and toluene.

High Efficiency Nondispersive Reactor for Two-Phase Reactions

A novel continuous static reactor concept improves mass transfer in two-phase chemical reactions between 1 and 2 orders of magnitude. The current paradigm for chemical reactions between two liquids requires energy-intensive mixing to disperse droplets of one phase in the continuous phase. The new reactor contacts a continuous free phase with a continuous phase constrained to a multitude of fibers. Phases come out of the reactor cleanly separated. An etherification reaction, a dehydrochlorination reaction, a transesterification reaction, and a vegetable oil neutralization were evaluated in fiber reactors. High conversions of starting materials to products were observed in minutes. Benefits of the new reactor complement the benefits of phase transfer catalyzed reactions.

Three Phase Catalytic Reactions: Role of Omega Aqueous Phase in Solid-Liquid Phase Transfer Catalyzed Etherification of 2'- Hydroxy Acetophenone

Phase Transfer Catalyst (PTC) is used in more than 600 commercial processes, with wide ranging applications in the pharmaceuticals, agrochemicals, polymer industries. Despite thousands of publications on the PTC, several intricacies of PTC in reactions are not understood or properly modeled. Liquid-liquid (L-L) PTC is inferior to solid-liquid (S-L) phase transfer catalyzed reactions, which in turn can be converted into Solid (reactant)-Liquid-(aqueous omega)- Liquid (organic) using trace quantities of water to realize 100% selectivity to the product. There is great enhancement in rates of reactions in comparison with corresponding S-L or L-L PTC. Thus, the O-alkylation of sodium salt of 2'-hydroxy acetophenone was achieved using 1-bromopentane using tetrabutylammonium bromide as the catalyst at 90 0C.2’-Pentyloxy acetophenone is used as a starting material for synthesis of fungicides. The current study deals with the efficacy of so-called omega phase with special emphasis on kinetic and modeling aspects.

Co-catalysis in phase transfer catalyzed reactions (a concept paper)

In this short paper the concept of co-catalysis in phase transfer catalyzed reactions is presented. It was shown that difficulties in the application of phase transfer catalysis for reactions of nonlipophilic inorganic anions such as hydroxide and fluoride anions can be efficiently eliminated when carried out in the presence of co-catalysts. On selected examples it was shown that numerous processes catalyzed by transition metals are substantially improved when carried out in the two-phase systems in the presence of phase transfer catalysts. Modus operandi of such co-catalytic systems varied depending on the kind of transition metal catalyzed process.

A more Efficient Starch Degradation by the Combination of Hydrolase and Transferase Activities of α‐Amylase and Cyclomaltodextrin Glucanotransferase

Abstractα‐Amylases catalyze the hydrolysis of internal α‐(1→4) linkages of glucose polymers as their main reaction; however, some α‐amylases catalyze transfer reactions in addition to hydrolysis. It has been observed that those α‐amylases capable of transferring glycoside residues are also those that generate low molecular weight products from their action on starch (i.e. saccharifying α‐amylases). In this paper the product profiles of a liquefying α‐amylase, a cyclomaltodextrin glucanotransferase and both enzymes acting together on starch and maltodextrins are compared. The increase in glucose and maltose concentration, when both enzymes act together, is due to the combined action of the transfer and hydrolytic activity of CGTase and the liquefying α‐amylase, respectively.

Chemical Modification of Functionalized Copolymers with Phosphonium Groups by Phase Transfer Catalysed Wittig Reactions

The interest for using polymers in Wittig reactions increased in the last years, because of their major advantages. Phase transfer catalyzed reactions are often more easily and cheaply carried out than conventional methods and they are therefore of particular interest. The phosphonium salts grafted on styrene-7%(5%)divinylbenzene copolymers used in this paper were obtained by quaternization polymer-analogous reaction. The degree of functionalization with quaternary phosphonium groups are relatively high, ranging from 1.84 to 1.98 mmoles/g of polymer. These grafted copolymers were used in liquid-liquid-solid Phase Transfer Catalysis(PTC)Wittig reaction. The yields were ranging from 1.84 to 1.98 mmoles of double bonds/gram of polymer.

Phase transfer catalysis (PTC): search for alternative organic solvents, even environmentally benign

The use of aliphatic esters, ethers and ketones such as dimethyl carbonate (DMC), methyl-tert-amyl ether (MTAE), 5-methyl-2-hexanone (MIAK), 4-methyl-2-pentanone (MIBK) as an alternative to traditional solvents (toluene, chlorobenzene, etc.) was explored as a strategy for performing phase transfer catalyzed reactions in organic media, even environmentally benign. Experimental data show that in these media the partition of the catalyst in the organic phase is comparable or higher than that in chlorobenzene, especially in the case of scarcely lipophilic methyltributylammonium (3) or tetrabutylammonium (4) salts (Eq. (1)). Anion reactivity under PTC conditions increases with decreasing the solvent polarity, in the order: ketone<ester≈chlorobenzene<ether. Such a trend is even more pronounced in the anhydrous solvent, where in the absence of any solvation it is possible to evaluate the intrinsic reactivity of the ion pair. Results clearly indicate the oxygenated solvents examined (MTAE, DMC, MIAK, MIBK) as a valid alternative to traditional media for PTC.

Kinetic modelling of mass transport limited phase transfer catalysed reactions

A simple but general mathematical model has been developed for analysing the rate data for displacement type liquid–liquid PTC reactions in laboratory reactors. The present model accounts for interphase mass transfer effects when present in a regime-independent manner. The model has been validated against published experimental rate data obtained by several workers in a number of reaction systems and in two different laboratory apparatus. The model predicts the time variation of the concentration of all the concerned species in either phase, given the initial composition of the two-phase reaction mixture, the type and the design of the reactor. The model can be used to study the sensitivity of the reaction rate towards the initial charge composition (PTC, organic/aqueous phase reactants, base, salt, if any), agitation speed, and phase hold-up ratio. It can also help to decide if mass transfer effect, in a given reaction under specified experimental conditions, is relevant and if so identify the regime. Finally, the model can be used to estimate the kinetic and distribution equilibria parameters that are of practical importance. This should be a useful tool for the design/scale-up of reactors for industrial PTC-based processes with a displacement reaction as the key step.

Phase transfer catalyzed reactions of crosslinked chloromethylated polystyrene with vanillin

Chloromethylated polystyrene was reacted with vanillin under phase transfer catalyzed conditions. This reaction was performed under different conditions, including variations of the phase transfer catalysts, the reaction solvent, the type of base, the reaction time and temperature. In addition, the effect of the reaction technique (i.e., solid–liquid–liquid and solid–liquid–solid systems) on the reaction conversion was studied. Polymer-supported vanillin was evaluated for its utilization in polymer analogue conversions by performing condensation reactions of the aldehyde functionality with malononitrile, ethyl cyanoacetate, cyanoacetamide, cyanothioacetamide, 2-aminophenol, hydrazine hydrate and hydroxylamine hydrochloride. In all cases, the reactions were followed up by means of FTIR spectroscopic analysis.

Syntheses, via precursor polymers, of polyethers containing 9,10-diacetoxyanthracene units or 9,10-anthraquinone units: chemical reactions of some of these polymers

Reaction of the bisphenol that is formally the Diels–Alder adduct of 2,6-dihydroxy-9,10-diacetoxyanthracene and dimethyl maleate with bis-acid chlorides and base in phase transfer catalysed reactions gives precursor polyethers. On heating the latter in a vacuum at 250–280°C retro-Diels–Alder reactions occur, with the loss of dimethyl maleate, to afford polymers containing 9,10-diacetoxyanthracene residues. Treating the precursor polyethers with sodium ethoxide in N,N-dimethylformamide converts them into soluble polymers containing units which are the disodium salts of the hydroanthraquinone. Aerial oxidation of these solutions gives polymers containing anthra-9,10-quinone (AQ) residues. Selected examples of the polymers containing 9,10-diacetoxyanthracene residues were similarly converted into the soluble polymers containing salt residues and thence into the corresponding AQ-containing polymers. Thus, we have shown that AQ-containing polymers can be prepared successfully by this novel type of precursor polymer approach.

Clay-Supported Liquid−Liquid−Solid Phase Transfer Catalysis: Synthesis of Benzoic Anhydride

Solid-supported phase transfer catalysed reactions typically involve polystyrene supports cross-linked with divinyl benzene. The use of commercially available clay as a support for the PTC reaction is attractive. This paper reports the preparation of benzoic anhydride from benzoyl chloride and sodium benzoate using clay-supported quaternary ammonium salts at 30 °C. The selectivity to the product is 100%. The mechanistic and kinetic aspects are also reported. The clay-supported catalyst was found to be more active than polymer-supported catalysts.

Interfacial area generation in two-phase systems and its effect on kinetics of phase transfer catalyzed reactions

Rigorous treatment of PTC reaction kinetics requires a knowledge of how the system is affected by changes in interfacial area generation since this variable strongly affects the rates of the transfer step. Here, a simple equation is derived for estimation of interfacial area generation in laminar-flow liquid-liquid systems. While derivation of this equation did not consider many of the sophisticated and relevant phenomena which affect interfacial area generation, particularly those which occur at higher stirring speeds, the equation is highly useful for mathematical simulation of PTC kinetics to determine expected apparent reaction rate - stirring rate profiles. The equation also indicates a reciprocal relationship between interfacial tension and the rates of PTC reactions for which the transfer step is rate controlling. Calculation results are shown to be consistent with reported experimental data.

Phase transfer catalyzed reactions of chloroform with electrophilic alkenes. Effect of solvent on reaction course

Reaction of chloroform with acrylic esters 1a-g, carried out in the presence of 50% aq NaOH, benzyltriethylammonium chloride (TEBACl) as a catalyst in heptane, gives exclusively adducts of trichloromethyl anion 2a-g with good yields. The same reaction carried out in the absence of solvent yields a mixture of products.

Triphase catalysis: a new rotating disk contactor for measuring mass transfer coefficients

Triphase catalysis (TPC) is a practically attractive way of carrying out phase transfer catalyzed reactions. The analysis of triphase catalytic systems requires a knowledge of mass transfer coefficients, but no correlations for estimating these are available. Therefore, a new rotating disk contactor (RDC) for measuring the external mass transfer coefficients of TPC systems has been designed and operated. Details of the design and construction of the contactor are discussed. In order to test the apparatus, experiments were carried out on a test system: synthesis of benzyl acetate from benzyl chloride and sodium acetate with polymer supported tributylmethylammonium chloride as the immobilized phase transfer catalyst. This reaction was found to be mass transfer controlled at low agitation speeds, and it was therefore possible to determine the external mass transfer coefficient as a function of the bulk agitation speed. The values ranged from 1.4×10 -3 to 2.0×10 -3 cm/min.