Phase transfer agents. I. Transfer of permanganate,periodate, and cyanate ions from aqueous to organic phases. Preparation of quaternary onium periodates

Several quaternary ammonium and phosphonium halides have been shown to be useful phase transfer agents (PTA) for the efficient transport of permanganate, periodate, and cyanate ions from aqueous to organic phases (benzene and/or methylene chloride). Chemical and spectral methods of analysis were used to measure ion transfer quantitatively and to assess the relative efficiency of PTA.     

A surfactant-like ionic liquid with permanganate dissolved as a highly selective epoxidation system

A ligand-free catalytic epoxidation system using permanganate in a surfactant-like ionic liquid (IL) medium was developed. The results indicate that the IL takes crucial effects in the epoxide selectivity. The loading of permanganate is also found critical in preventing over-oxidation of epoxides. The system with 0.3 mol% permanganate and 3.5-equivalent CH₃CO₃H is able to achieve excellent yields and selectivity of epoxides. The study of epoxidation with KMnO₄ in IL medium reveals an unusual oxidation behavior of permanganate not found in traditional solvents.     

Electrosynthesis in systems of two immiscible liquids and a phase transfer catalyst. VI. The influence of zinc chloride on the chlorination of naphthalene

The influence of zinc chloride on the chlorination of naphthalene by electrolysis in a water-methylene chloride emulsion and using tetrabutylammonium ion as a phase transfer catalyst is described. It is shown that when the aqueous medium contains both NaCl and ZnCl₂ it is the anion ZnCl ₄ ^2– which transfers into the organic phase and it is confirmed that the presence of ZnCl₂ in the electrolyte is, indeed, beneficial. The electrolyses have been carried out in both divided and undivided cells and in both the organic yield of 1-chloronaphthalene can exceed 80% but the former is better from the viewpoint of speed of electrolysis; in the divided cell, the conversion was 85% (cf. typically 60% in the undivided cell) after the passage of 2.3 F mol^–1 of naphthalene. Possible mechanisms for the effect of ZnCl[in2] are discussed.On leave of absence from the Faculty of Technology, University of Banja Luka, Yugoslavia.     

Chemistry of epoxy compounds. xxii. preparation of some long-cham 2-oxazolidones

Long-chain aliphatic compounds containing the 2-oxazolidone moiety have been prepared fromcis- andtrans- 9 octadecene, methyl oleate, and elaidate, oleyl and elaidyl alcohols, and several long-chain terminal epoxides. The 2-oxazolidones prepared are substituted in the 4-, 4,5-, or 3,5-positions. The first two groups of oxazolidones are obtained by pyrolysis of β-iodocarbamates, prepared from terminal and internal monoun-saturated compounds respectively by the addition of iodine isocyanate and by reaction with meth-anol. The last group is prepared by heating ter-minal epoxides with organic isocyanates in DMP containing a catalytic quantity of tetramethyl-ammonium iodide or lithium chloride. Structures have been confirmed by elemental and spectral analysis. Presented at the AOCS Meeting, Washington, D.O., March 1968. Taken from the thesis of M. E. D. in partial -fulfillment of the require-ments for the Ph.D. degree, Temple University, June 1967. Recent work has shown that the ring closure is stereoselective, not stereospecific.     

Anodic substitutions in emulsions under phase transfer catalysis conditions. I. Cyanation of dimethoxybenzenes

An emulsion electrolysis technique in the two-phase system water-dichloromethane containing NaCN and a phase transfer agent (PTA) has been examined with 1,2- and 1,3-dimethoxybenzenes as a function of various parameters (nature of Q⁺, X^–, anodic potential, cyanide ion concentration in the organic phase, preparative current potential curves). The anodic cyanation results indicate that the anode wetting phenomena, the extraction of cyanide ion and the competitive oxidation of X^– are the determining factors. It is shown that the best criterion for a successful anodic cyanation is to operate under conditions of maximum coverage of the anode by the organic layer. Among all the PTA studied (cetyltrimethylammonium bromide,nBu4N⁺HSO ₄ ^– ,nBuP⁺₃Br^–, benzethonium chloride and A 336), A 336, a very hydrophobic PTA, affords the best chemical (81%) and current (77%) yields with 1,2,-dimethoxybenzene.     

Epoxidation of ethylenic linkages by chromic acid IV. Oxidation of triaryl olefins by chromium trioxide

The oxidation of 1,1,2-triphenylbut-1-ene by chromium trioxide in acetic anhydride gives 1,2-epoxy-1,1,2-triphenylbutane with fission products and 1,1,2-triphenylacetylethylene. Cis- and trans-1-p-chlorophenyl-1,2-diphenylprop-1-ene yield crystalline epoxides in satisfactory yields under similar conditions. The epoxides are stable towards aqueous sulphuric acid. 1,1,2-Triphenylethylene, 1,1-di-(p-chlorophenyl)-2-phenylethylene and 1,1-di-(p-bromophenyl)-2-phenylethylene are similarly oxidised but the epoxides are hydrated to the glycols by the action of aqueous sulphuric acid. Chromic acid in aqueous sulphuric acid brings about oxidative fission of the double bond without any rearrangement.     

Complexation of poly(methyl methacrylate-g-propylene oxide) and alkali-metal ions

Summary Copolymers of poly(methyl methacrylate-g-propylene oxide) with grafted branches having different molecular weights were complexed with K⁺, Na⁺ and Ca²⁺. The efficiency of the graft copolymers in binding cations was evaluated from salt distribution equilibria in water-methylene chloride. Among the used cations, K⁺ was more easily complexed than Na⁺ and Ca²⁺.     

Using full‐factorial design analysis and response surface methodology to better understand the production of cationized chitosan from epoxides

The production of cationized chitosan derivatives via reaction between chitosan and quaternary epoxides has the advantage of producing substances with a better regioselectivity and with structures that do not change as a function of pH, unlike N,N,N‐trimethylchitosan. Moreover, this reaction allows the production of cationized derivatives having different hydrophobic/hydrophilic balances because quaternary epoxides with different alkyl chains can be used in this reaction. The effects of reaction parameters, namely time, temperature and glycidyltrimethylammonium chloride (GTMAC)/chitosan (Ch) molar ratio, on the structural and hydrodynamic characteristics of N‐(2‐hydroxy)propyl‐3‐trimethylammoniumchitosan chloride (ChCat) and on reaction yield were evaluated using chemometrics and response surface methodology (RSM). Structural characterization and determination of intrinsic viscosity were realized using spectroscopic techniques (Fourier transform infrared and ¹H NMR) and capillary viscometry, respectively. The polynomial functions and RSM developed from 2³ full‐factorial analysis show the influence of the reaction parameters on the characteristics and properties of the ChCat produced, permitting the choice of appropriate reaction conditions to suit its desired application. Results show, as an example, that when the N‐substitution is carried out for 6 h at 50 °C employing excess of GTMAC (GTMAC/Ch = 4:1), water‐soluble moderately substituted ( = 33.0%) ChCat ([η] = 293.4 mL g^?1) can be produced with moderate reaction yield (30.9%). Furthermore, as GTMAC is the simplest quaternary epoxide, the study of its reaction with chitosan serves as a template for more complex quaternary epoxides as they may be used for the production of new cationized chitosan derivatives possessing alkyl chains with various chain lengths. © 2016 Society of Chemical Industry     

Metabolically blocked analogs of housefly sex pheromone: I. Synthesis of alternative substrates for the cuticular monooxygenases

Cuticular monooxygenases in the cuticle of the female houseflyMusca domestica oxidize (Z)-9-tricosene to m-9,10-epoxytricosane and to (Z)-9-tricosen-14-one. One possible explanation for these two products is that a single monooxygenase accepts the alkene substrate in two different orientations. Eleven analogs of (Z)-9-tricosene bearing methyl substituents, cyclopropyl groups, fluorine substituents, deuterium substituents, and additional double bonds were synthesized to probe the substrate requirements of this monooxygenase system. In addition, the 11 corresponding epoxides were prepared to aid in identification of the metabolites of each modified alkene.     

Synthesis and characterization of hyperbranched polytriazole via an ‘A2 + B3’ approach based on click chemistry

BACKGROUND: The ‘A₂ + B₃’ type of polymerization has been demonstrated to be an alternative route towards hyperbranched polymers. Some highly crosslinked hyperbranched polymers have been prepared via copper(I)‐catalyzed click reactions of multivalent azides and alkynes. To obtain hyperbranched polymers without gelation and develop the A₂ + B₃ type of polymerization based on click reactions, the specific reaction conditions need to be investigated. RESULTS: In this work, a hyperbranched polytriazole (hb‐PTA) was synthesized through the A₂ + B₃ approach using a click reaction. 4‐N,N′‐bis(2‐azidoethyl)amino‐4′‐nitroazobenzene and 1,3,5‐tris(alynyloxy)benzene were synthesized for use as the A₂ and B₃ monomers, respectively. This was a ‘one‐pot’ polymerization carried out using a slow‐addition method. The obtained hb‐PTA was soluble in common organic solvents. The molecular structure was characterized using ¹H NMR, Fourier transform infrared and gel permeation chromatography analyses. The degree of branching of hb‐PTA was determined to be around 0.50. CONCLUSION: The hb‐PTA was successfully synthesized via the A₂ + B₃ approach based on a click reaction. The polymerization conducted in dilute solution adopting slow addition of A₂ to B₃ resulted in hb‐PTA in the absence of gelation. The obtained hb‐PTA exhibited high thermal stability. Copyright © 2008 Society of Chemical Industry     

(Salen)chromium Complex Mediated Asymmetric Ring Opening of meso‐ and Racemic Epoxides with Different Fluoride Sources

The asymmetric ring opening of five meso‐ and three racemic epoxides with different fluorinating reagents in the presence of stoichiometric or slightly sub‐stoichiometric amounts of Jacobsen's enantiopure (salen)chromium chloride complex A gave the corresponding optically active vicinal fluorohydrins. Silver fluoride was used as one of the fluoride sources either in the presence of Bu₄N⁺H₂F₃⁻ in diethyl ether or in acetonitrile. The latter reactions starting from cyclohexene oxide ( 1 ) showed maximum 72% ee in the formed fluorohydrin 2 isolated in 90% yield. From other meso‐epoxides such as cyclopentene oxide and cycloheptene oxide the corresponding fluorohydrins were isolated in 80% and 82% yield with 65% and 62% ee, respectively. In case of ring opening under similar conditions of the racemic styrene oxide or phenyl glycidyl ether 83% and 75% of the fluorohydrins with fluorine in the primary position were isolated with 74% ee and 65% ee, respectively. Tetrahydronaphthalene oxide yielded a 2:1 mixture of trans‐ (23% ee) and cis‐2‐fluoro‐3,4‐benzocyclohexenol (2% ee) suggesting competing S_N2 and S_N1 type ring openings. Other epoxides such as cyclooctene oxide, cis‐stilbene oxide and α‐methylstyrene oxide did not react or gave the fluorohydrins with very small enantiomeric excess.     

Conformationally Rigid Chiral Bicyclic Skeleton‐Tethered Bipyridine N,N′‐Dioxide as Organocatalyst: Asymmetric Ring Opening of meso‐Epoxides

The conformationally rigid chiral bicyclic skeleton tethered bipyridine N,N′‐dioxide (−)‐ 9 has been designed, synthesized and examined as an organocatalyst in the enantioselective ring opening of meso‐epoxides using tetrachlorosilane (SiCl₄). The catalyst (−)‐ 9 is found to exhibit good enantioselectivity for substituted cis‐stilbene epoxides; whereas, the saturated cyclic meso‐epoxides display a moderate enantioselectivity. At −30 °C in chloroform, the catalyst (−)‐ 9 with 0.5 mol % loading generated the chlorohydrins in up to 97 % yield with up to 93 % ee. The possible creation of transient axial chiral environment around hypervalent silicon species due to the presence of conformationally rigid chiral bicyclic skeleton tethered bipyridine N,N′‐dioxide may be responsible for such enantioselectivity observed in the desymmetrization of meso‐epoxides.

     

Stabilization of poly(vinyl chloride). VIII. Synergisms between epoxy compounds and metal soaps

Effects of bisphenol A type epoxy compounds involving various average molecular weights on the zinc stearate/calcium stearate and the cadmium stearate/barium stearate synergetic soaps induced thermal stabilization of poly(vinyl chloride) (PVC) were investigated by colorimetry. The remarkable stabilization effects of epoxides could not be observed on the PVC films without synergetic soaps, while the stabilization of PVC was markedly enhanced by combined use of epoxides and synergetic soaps. The appearance of excessive coloration of cool color producing metal chloride–polyene complexes which were an origin of abrupt discoloration of stabilized PVC was retarded by using epoxides together with synergetic soaps. Moreover, as for PVC with or without synergetic soaps, the epoxy compounds did not inhibit the formation of longer polyene chains which were a chromophore for yellow orange of aged PVC. Further colorimetries and IR or X-ray photoelectron spectroscopies on the various PVC containing epoxy compounds and zinc chloride indicated that the epoxy groups caught the zinc chloride. The synergetic effect between epoxy compounds and synergetic metal soaps is ascribed to the action that the epoxides serve as an acceptor for the excessive cool color producing metal chloride produced from zinc stearate and cadmium stearate to retard the abrupt discoloration of stabilized PVC.     

Separation of cation–anion mixture using micellar-enhanced ultrafiltration in a mixed micellar system

Aqueous solution containing copper (cation) and potassium permanganate (anion) was treated by ultrafiltration using mixed micellar system comprising of sodium dodecyl sulfate and cetylpyridinium chloride. Simultaneous separation characteristics of both cation and anion, as well as permeate flux were studied for various operating conditions, namely, transmembrane pressure drop and cross-flow rate. The study was carried over a wide concentration range of both solutes. In the mixture, copper concentration was in the range from 0.05 to 4.0 kg/m³ and that of potassium permanganate was 0.05 to 0.25 kg/m³. Retention of copper was in the range of 90–100% and that of potassium permanganate was 96–99%. Permeate flux was found to be less in the mixed micellar system compared to single surfactant system. A four step chemical treatment process was proposed to recover and reuse the surfactants.     

DSC and 13C-NMR studies of the imidazole-accelerated reaction between epoxides and phenols

The imidazole-accelerated reaction between epoxides and phenols has been studied through DSC and ¹³C-NMR of model compounds. The selectivity of the accelerator has been found to be strongly dependent on its concentration. If a low amount of accelerator is used, the reaction takes place almost exclusively through the addition of phenols to epoxides even if the latter are used in excess. However, a larger amount of accelerator will cause the secondary hydroxyls (produced by the main reaction) to react with the epoxides. In any case, the lower reactivity of the secondary hydroxyls prevents them from reacting to any significant extent as long as there are any phenols present. When polyfunctional resins are used, the effect of the selectivity of the reaction on the properties of the crosslinked network is very clear. If a low amount of accelerator is used (to promote only the epoxy–phenol reaction), the maximum glass transition temperature (T_g) occurs when the epoxides and phenols are stoichiometrically balanced, reaching 178°C. However, when an excess of epoxides over phenols is used, along with a larger amount of accelarator, the maximum T_g increases its value to 199°C.     

Sulfonated poly(phenylene ether ether sulfone) membrane tailored with layer-by-layer self-assembly of poly(diallyldimethylammonium chloride) and phosphotungstic acid for DMFC applications

Poly(diallyldimethylammonium chloride) (PDDA) and phosphotungstic acid (PTA) were used as cationic and anionic polyelectrolyte layers, respectively, in an alternating fashion to enhance the methanol barrier property and oxidative stability of sulfonated poly (phenylene ether ether sulfone) (SPEES) proton exchange membranes (PEMs). The multilayer PEMs were characterized by AFM, FTIR, and AC impedance spectroscopy. Methanol permeability of the multilayered membranes was found to be much lower than the bare SPEES membrane. The multilayered membranes displayed significantly improved oxidative stability and dimensional stability compared to pristine SPEES membrane. Conversely, the water uptake (%) and proton conductivity (S cm⁻¹) of the prepared membranes decrease to some extent with increasing the PDDA/PTA bilayers in comparison to the pristine SPEES membrane. The maximum relative selectivity (2.23 × 10⁴ S cm⁻³ s) and retained weight (88.9%) were observed for SPEES-[PDDA/PTA]₅ multilayered membrane. The obtained results exposed the possibility of SPEES-[PDDA/PTA]₅ multilayered membrane to serve as high-performance PEMs in direct methanol fuel cells. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47344.     

Biocatalytic Potential of the Epoxide Hydrolase from Agrobacterium radiobacter AD1 and a Mutant with Enhanced Enantioselectivity

Optically pure epoxides are useful synthons for a variety of biologically active compounds. The epoxide hydrolase obtained from Agrobacterium radiobacter AD1 hydrolyses racemic aryl epoxides with moderate and aliphatic epoxides with low enantioselectivity. The three‐dimensional structure of this enzyme indicates that two tyrosine residues interact with the epoxide oxygen. Mutating one of these, tyrosine 215, to a phenylalanine (Y215F) resulted in an enzyme with increased enantioselectivity towards aryl epoxides. The relatively strong decrease in activity towards the remaining enantiomers makes this enzyme a much better biocatalyst than the wild‐type enzyme for the preparation of optically pure (S)‐styrene oxide derivatives.     

The reaction of picric acid with epoxides. II. The detection of epoxides in heated oils

A colorimetric method, based upon the reaction of the oxirane group with picric acid, was used to determine the epoxide content of heated vegetable oils. The picration method is particularly suitable for measuring small quantities of epoxide because it is much more sensitive than the common titrimetric methods, and it is not subject to interference from cyclopropene, conjugated dieneols, or α, β-unsaturated carbonyls. Thin-layer chromatography was used to separate mixtures of picrated, epoxidized methyl esters. Separation ofcis- andtrans-methyl epoxystearate, methyl epoxyoleate, and methyl diepoxystearate in a mixture of these four esters was achieved in this manner. The presence of saturatedcis- andtrans-epoxystearates and unsaturated epoxides was demonstrated in heated vegetable oils. Presented, in part, at the AOCS Meeting in Cincinnati, October 1965.     

Hydrolytic Kinetic Resolution of Epoxides Catalyzed by Chromium(III)‐endo,endo‐2,5‐diaminonorbornane‐salen [Cr(III)‐DIANANE‐salen] Complexes. Improved Activity,Low Catalyst Loading

The hydrolytic kinetic resolution (HKR) of terminal epoxides, using chiral chromium(III )‐salen catalysts based on DIANANE (endo,endo‐2,5‐diaminonorbornane), was studied. A broad substrate scope was found for the chromium(III )‐DIANANE catalysts, and very low loadings (down to 0.05 mol %) were needed to achieve high enantiomeric purities of both the remaining epoxides and the product diols (up to >99 % ee). Besides monosubstituted epoxides, 2‐methyl‐2‐n‐pentyloxirane, which is an example for 2,2‐disubstituted epoxides, could be ring‐opened in an asymmetric fashion with water in the presence of an electronically tuned chromium(III )‐DIANANE complex.     

Progress in the research and development of p-xylene liquid phase oxidation process

The process of p-xylene liquid phase oxidation to produce purified terephthalic acid (PTA) involves a series of liquid phase radical reactions, chemical absorption, reactive crystallization, and evaporation. A commercial PTA production flow sheet includes a number of unit operations, which construct a complex process system. In this paper, a review of research and development (R&D) works on PTA process carried out in Zhejiang University during recent years is introduced. The works cover the oxidation and crystallization kinetics, gas-liquid mass transfer and evaporation, reactor modeling, database development, novel reactor design, process modeling, simulation, and optimization. The author emphasizes the viewpoint through this case study that chemical reaction engineering should be developed to process system engineering to extend its scope, and particular attention should be paid on reactor and process modeling.