Absence Of Phase Transfer Catalyst Research Articles

Alkali hydrolysis of wool fibres using microwave irradiation as a recycling approach for handling wool-waste

The aim of the present work is to investigate the influence of microwave irradiation on alkali hydrolysis, under various thermochemical conditions, of wool fibres. This perspective seems to be a promising alternative for the valorization of wool waste. The reaction yield is calculated in every case in order to determine the optimum hydrolysis conditions. The solid residue, as well as the filtrate, are subjected to instrumental chemical analysis in order to identify and isolate useful products. The optimal conditions for the hydrolysis of wool resulted to be the use of 5% w/v NaOH, microwave treatment for 10 min in absence of phase-transfer catalyst. In addition, the analysis in the Pyrolysis-Gas Chromatography/Mass Spectrometry (Py-GC/MS) allowed the identification of certain small molecules like N2, H2S, NH3, C6H5OH, C4H9NO and larger ones like amino acids, such as alanine, cystine, proline, valine and leucine. Additionally, the content of wool hydrolysate was specified upon identifying several substituted products of tyrosine, proline and alanine amino acids. Liquid Chromatography–Orbitrap High-Resolution Mass Spectrometry (LC–Orbitrap HRMS) was also employed to identify the components present in the wool hydrolysate, detecting mainly various dipeptides as well as leucylproline and cysteic acid. In this light, the amino acids produced by wool alkali hydrolysis degradation could valorise the wool waste once inserted in industrial chemistry, as a prominent alternative for “greener” adhesives of two components, outlining by these means the feasibility of a practically sustainable circular economy.

Microwave assisted Williamson Ether Synthesis in the absence of Phase Transfer Catalyst

An efficient, economical and eco-friendly microwave assisted protocol for protection of phenolic hydroxyl group is reported. The protocol enables preparation of diphenyl ethers by treatment of various phenols with 2,4-dinitrochlorobenzene in absence of any auxiliary substance such as phase transfer catalyst. This microwave assisted Williamson reaction is more practical and greener way for preparing diphenyl ethers which are useful as agrochemicals.

Phase-transfer catalysis enhanced remediation of trichloroethylene polluted groundwater by potassium permanganate

ABSTRACT As one of the remediation reagents, potassium permanganate (KMnO4) is injected to the aquifer, degrading trichloroethylene (TCE) by chemical oxidation. This study investigated the kinetics of TCE degradation by series of batch experiments, as well as the influence of medium size. Moreover, phase-transfer catalyst (PTCs), such as pentyltriphenylphosphonium bromide (PTPP) and sodium hexametaphosphate (SHMP) were used for enhancing oxidation. The batch experimental results showed that in the absence of PTC, the removal efficiency of TCE was 36.14% and 86.79% within 4 and 30 min, respectively. However, the removal rate of TCE was up to 67.48% and 49.90% within 4 min for 15 mol% PTPP- and SHMP-added system, respectively. The results indicated that PTPP and SHMP promoted the depletion of to oxidize DNAPL TCE, but its effectiveness varied with the addition ratio of PTPP or SHMP. Its promotion was more remarkable when PTC added with a higher proportion. The alleviation of MnO2 by phosphates (, and ) or PTC in the presence of media was qualitatively investigated. Results showed that the content of MnO2 in the dissolved phase during the same reaction period decreased by PTC. Moreover, and SHMP have apparent beneficial effects of reducing MnO2 formation. The presence of aquifer media has a pH buffer and a negative influence on the reaction between TCE and the oxidant; moreover, as particle size of media decreased, the negative effect increased.

K5PW11NiO39‐catalyzed oxidation of benzyl alcohol with hydrogen peroxide

AbstractIn this work, we synthesized a series of metal‐substituted potassium heteropolyacid salts and investigated its catalytic activity on oxidation of benzyl alcohol with H2O2 under homogeneous (CH3CN) and biphasic (toluene/water) conditions. The Keggin heteropolyacids were converted to lacunar salts (i. e., K7PW11O39; K7PMo11O39 and K8SiW11O39), which had their vacancies filled with metal cations (i. e., Al3+, Fe3+, Co2+, Cu2+, and Ni2+), generating the metal‐substituted salts. The K5PW11NiO39 proved to be the most efficient catalyst. The synergic effect raised between the PW11O397− anion and Ni2+ cation improved the redox properties and the activity of the catalyst. The K5PW11NiO39 catalyst was able to promote the benzyl alcohol oxidation with hydrogen peroxide in biphasic conditions in the absence of phase transfer catalyst. Benzaldehyde and benzoic acid were the main products. The effects of main reaction parameters were assessed. The K5PW11NiO39 catalyst was successfully recovered and reused without losing activity.

Catalytic Condensation of Carbonyl Compounds during the Synthesis of Cyclohexanone in the Production of Caprolactam

Kinetic features of the condensation processes of carbonyl and unsaturated impurities in cyclohexanone have been studied using model mixtures in a heterophase system in the presence and absence of phase-transfer catalysts. It has been shown that linear aldehydes are condensed with cyclohexanone in the heterophase system in the presence and absence of phase-transfer catalysts under mild conditions (30–50°C). Noncarbonyl unsaturated compounds (e.g., 2-cyclohexene-1-ol) can be removed only at temperatures above 100°C in the presence of acidic catalysts (e.g., high-temperature sulfonated cation-exchange resins). Unsaturated cyclic ketones are characterized by both alkylation reactions over acid catalysts and aldol condensation reactions in the presence of an alkali, thereby suggesting the possibility of their elimination at different cyclohexanone purification steps. The theoretical models built can be used to develop an effective cyclohexanone purification technology that will substantially enhance the manufacturability of high-purity caprolactam and polyamide.

ChemInform Abstract: Sodium Hypochlorite Pentahydrate (NaOCl·5H2O) Crystals; An Effective Re‐Oxidant for TEMPO Oxidation.

Abstract The novel oxidant of sodium hypochlorite pentahydrate (NaOCl·5H2O), which is now available for industrial and laboratory use has several advantageous properties. The crystalline material has 44% of NaOCl, contains minimal sodium hydroxide and sodium chloride, and the aqueous solution indicates pH 11–12. Herein, NaOCl·5H2O crystals are examined for use as an oxidant for primary and secondary alcohols, with or without nitroxyl radicals, in the presence or absence of phase-transfer catalysts. The pentahydrate crystals alone (without nitroxyl radicals) demonstrate a powerful oxidizing ability, converting secondary alcohols to the corresponding ketones. In the presence of TEMPO (2,2,6,6-tetramethylpiperidine 1-oxyl) or 1-Me-AZADO (1-methyl-2-azaadamantane N-oxy radical), sterically hindered secondary alcohols are oxidized without pH adjustment. A proposed mechanism for the oxidation is discussed.

Sodium hypochlorite pentahydrate (NaOCl·5H2O) crystals; An effective re-oxidant for TEMPO oxidation

The novel oxidant of sodium hypochlorite pentahydrate (NaOCl·5H2O), which is now available for industrial and laboratory use has several advantageous properties. The crystalline material has 44% of NaOCl, contains minimal sodium hydroxide and sodium chloride, and the aqueous solution indicates pH 11–12. Herein, NaOCl·5H2O crystals are examined for use as an oxidant for primary and secondary alcohols, with or without nitroxyl radicals, in the presence or absence of phase-transfer catalysts. The pentahydrate crystals alone (without nitroxyl radicals) demonstrate a powerful oxidizing ability, converting secondary alcohols to the corresponding ketones. In the presence of TEMPO (2,2,6,6-tetramethylpiperidine 1-oxyl) or 1-Me-AZADO (1-methyl-2-azaadamantane N-oxy radical), sterically hindered secondary alcohols are oxidized without pH adjustment. A proposed mechanism for the oxidation is discussed.

Microwave-Assisted Solid-Liquid Phase Alkylation of Naphthols

The microwave promoted alkylation of 1- and 2-naphthols with benzyl, butyl, ethyl and isopropyl halides in the presence of an alkali carbonate may result in O- and C-alkylated products. The alkylations were O-selective in the presence of K2CO3 in acetonitrile as the solvent and in the absence of phase transfer catalyst. The alkylations utilizing butyl and ethyl halides were also O-selective in solventless accomplishment and in the presence of triethylbenzylammonium chloride. Keywords: O-alkylation, C-alkylation, microwave, phase transfer catalyst.

Parametric study and optimization of in situ transesterification of Jatropha curcas L assisted by benzyltrimethylammonium hydroxide as a phase transfer catalyst via response surface methodology

In the present work, non-edible oil source, Jatropha curcas oil was used with base catalyzed methanol and ethanol to produce biodiesel using in situ transesterification assisted by Benzyltrimethylammonium hydroxide (BTMAOH) as a phase transfer catalyst (PTC). Experimental investigation showed that base catalyzed in situ transesterification reaction rate was enhanced with the use of BTMAOH as a PTC. During the experiment fast formation of biodiesel was observed in relatively shorter time for PTC assisted reaction as compared to the reaction in the absence of PTC. The effect of individual reaction parameters was investigated using response surface methodology (RSM). Optimum operating conditions were also found statistically. Weight fractions of 89 ± 0.7% fatty acid methyl esters (FAME) yield and 99.4 ± 0.4% fatty acid ethyl esters (FAEE) yield were produced at optimum reaction condition. The fuel quality of FAME and FAEE was investigated against the fuel quality specification set by ASTM D6751 and EN-14214 standards.

Synthesis and properties of polycyclic phosphonate resins using one-pot method under ultrasound irradiation

Novel polycyclic phosphonates were first synthesized from novolac phenol formaldehyde (PF) resins under ultrasound irradiation in the absence of phase transfer catalyst (PTC). Experimental results demonstrated that ultrasound can accelerate the cycle condensation of the novolac PF resin in good yield. The chemical structure of the synthesized polycyclics was characterized using Gel-permeation chromatography (GPC), Fourier transfer infrared (FTIR), 1H- and 31P-nuclear magnetic resonance (NMR). Thermal properties of these polycyclics were determined by TG/IR analysis. The results showed that the induced cyclical phosphonate resins can greatly inhibit the oxidative weight loss of the polycyclic phosphonates, leading to very high char yields at temperatures higher than 700 °C. The char yields remained still about 4 wt.% while the weight remaining of phosphonate-free phenol formaldehyde (PF) resin was almost 0% at 600 °C. This indicates that the synthesized polycyclic phosphonates could be the potential candidates as a flame retardant for the polymers such as polycarbonate, epoxy resin and poly(ethylene terephthalate) etc.

Solvent-Free Synthesis of N-Arylfulleropyrrolidine Derivatives Without Using Phase-Transfer Catalyst Under Microwave Irradiation

Several N-arylfulleropyrrolidine derivatives were synthesized via the direct solvent-free reactions of N-unsubstituted fulleropyrrolidines and nitrochlorobenzenes under microwave irradiation in the absence of phase-transfer catalysts. Their structures were confirmed by ultraviolet–visble, Fourier transform–infrared, 1H NMR, and mass spectrometry.

Liquid-phase hydrodechlorination of chlorobenzene by molecular hydrogen: The influence of reaction medium on process efficiency

Catalytic hydrodechlorination (HDCl) of chlorobenzene was carried out in a two-phase aqueous–organic solvent system and a single-phase solvent composed of saturated KOH solution in a secondary alcohol over Pd-based catalysts at 50 °C and atmospheric pressure of H2. It was shown that an aqueous–organic solvent system containing propan-2-ol and aqueous KOH increases catalyst activity by promoting mass transfer of the formed chloride ions to water phase that prevents catalyst deactivation. It is inferred that propan-2-ol favors hydrogen activation during the HDCl process. Use of the Pd catalysts based on hydrophobic carbon support enables chlorobenzene HDCl to proceed in a two-phase solvent at a satisfactory rate, even in the absence of phase-transfer catalysts.

Study of the microwave-assisted hydrolysis of nitriles and esters and the implementation of this system in rapid microwave-assisted Pd-catalyzed amination

Microwave-assisted hydrolysis of benzonitriles and methyl benzoates has been studied using a toluene/concd aq KOH two phase system in the presence and absence of phase transfer catalyst. Conditions to allow and avoid smooth hydrolysis could be identified. Based on the latter, the first microwave protocol which allows the rapid Pd-catalyzed amination of aliphatic amines with chlorobenzenes containing sensitive functional groups has been developed.

Kinetic Study of Synthesizing Bisphenol A Diallyl Ether in a Phase-Transfer Catalytic Reaction

Abstract In the synthesis of bisphenol A diallyl ether from bisphenol A and allyl bromide, the liquid–liquid mode of operation catalyzed by quaternary ammonium salts was carried out in an alkaline solution/organic solvent two-phase medium. The mono-substituted product was not detected during or after the reaction. In this work, a rational reaction mechanism is proposed and a kinetic model then established. The apparent rate constant of the organic-phase reaction was obtained from experimental data. The effects of the reaction conditions, including agitation speed, organic solvents, quaternary ammonium salts, inorganic salts, temperature, alkali compounds, amount of potassium hydroxide, and water on the conversion of allyl bromide, were investigated in detail. The presence of a small amount of tetrabutylammonium bromide (TBAB) in the chlorobenzene/water system produced a rate over several folds larger than that of the reaction system in the absence of phase-transfer catalyst. The presence of alkali compounds promoted the formation of alkoxide and enhanced the extractive efficiency due to the salting out effect. The present etherification via phase-transfer catalyst could operate at lower temperatures to avoid Claisen rearrangement, which usually occurs at higher temperatures. Rational reasons to account for the absence of mono-substituted product are explained satisfactorily. Peculiar phenomena in investigating the effects of the volume of organic solvent, amount of KOH, and the volume of water and alkali compounds on the apparent rate constants are also explained.

An Insight into the Reductive Cleavage of Tellurium-Tellurium Bond in Various 2,2′-Dipyridyl Ditelluride Using Hydrazine Hydrate

Reductive cleavage of tellurium-tellurium bond in various 2,2'-dipyridyl ditellurides using hydrazine hydrate (100%) both in the presence and absence of phase transfer catalyst is reported. A tentative mechanism of the reaction is also proposed.

Combined microwave and ultrasound assisted Williamson ether synthesis in the absence of phase-transfer catalysts

The combined microwave and ultrasound assisted Williamson reaction proves an efficient and ecologically valuable route for preparing ethers in the absence of organic auxiliary substances such as phase-transfer catalysts.

Azide and Cyanide Displacements via Hypervalent Silicate Intermediates.

Hypervalent azido- and cyanosilicate derivatives, prepared in situ by the reaction of trimethylsilyl azide or trimethylsilyl cyanide, respectively, with tetrabutylammonium fluoride, are effective sources of nucleophilic azide or cyanide. Primary and secondary alkyl halides and sulfonates undergo rapid and efficient azide or cyanide displacement in the absence of phase transfer catalysts with the silicate derivatives. Application of these reagents to the stereoselective synthesis of glycosyl azide derivatives is reported.

ChemInform Abstract: A ONE‐POT SYNTHESIS OF β‐LACTAMS BY THE REACTION OF β‐HALOACYL CHLORIDES WITH α‐AMINO ACIDS

AbstractDie Synthese der β‐Lactame (IV) aus den Acylaminosäuren (III) wird unter verschiedenen Bedingungen untersucht, z.B. ohne Katalysatoren oder bei Zusatz von Triethylbenzylammoniumchlorid oder auch Aminosäuren als Katalysatoren.

A one-pot synthesis of .BETA.-lactams by the reaction of .BETA.-haloacyl chlorides with .ALPHA.-amino acids.

A one-pot synthesis of β-lactams (4) was successfully achieved by the reaction of β-haloacyl chlorides (1) with α-amino acids (2) in aqueous 5% sodium hydroxide solution in the absence of phase transfer catalyst in yields of 43-91%.