Phosphorus Pentoxide/methanesulfonic Acid Research Articles

A Novel High Temperature Fuel Cell Proton Exchange Membrane with Nanoscale Phase Separation Structure Based on Crosslinked Polybenzimidazole with Poly(vinylbenzyl chloride)

A semi-aromatic polybenzimidazole (DPBI) is synthesized via polycondensation of decanedioic acid (DCDA) and 3,3-diaminobenzidine (DAB) in a mixed phosphorus pentoxide/methanesulfonic acid (PPMA) solvent. Ascribing to in-situ macromolecular crosslinker of ploly((vinylbenzyl chloride) (PVBC), a robust crosslinked DPBI membrane (DPBI-xPVBC, x refers to the weight percentage of PVBC in the membrane) can be obtained. Comprehensive properties of the DPBI and DPBI-xPVBC membranes are investigated, including chemical structure, antioxidant stability, mechanical strength, PA uptake and electrochemical performances. Compared with pristine DPBI membrane, the PA doped DPBI-xPVBC membranes exhibit excellent antioxidative stability, high proton conductivity and enhanced mechanical strength. The PA doped DPBI-10PVBC membrane shows a proton conductivity of 49 mS cm-1 at 160 °C without humidification. Particularly, it reveals an enhanced H2/O2 single cell performance with the maximum peak power density of 405 mW cm-2, which is 29% higher than that of pristine DPBI membrane (314 mW cm-2). In addition, the cell is very stable in 50 h, indicating the in-situ crosslinked DPBI with a macromolecular crosslinker of PVBC is an efficient way to improve the overall performance of HT-PEMs for high performance HT-PEMFCs.

Synthesis of benzofurans from the cyclodehydration of α-phenoxy ketones mediated by Eaton’s reagent

Cyclodehydration of α-phenoxy ketones promoted by Eaton’s reagent (phosphorus pentoxide–methanesulfonic acid) is used to prepare 3-substituted or 2,3-disubstituted benzofurans with moderate to excellent yields under mild conditions. The method provides a facile access to benzofurans from readily available starting materials such as phenols and α-bromo ketones. The reaction is highly efficient, which is attributed to the good reactivity and fluidity of Eaton’s reagent. The reaction can be applied to prepare naphthofurans, furanocoumarins, benzothiophenes, and benzopyrans.

Solvent-free synthesis of dibenzo[b,j][1,10]phenanthroline derivatives using Eaton’s reagent as catalyst

ABSTRACTA new class of dibenzo[b,j][1,10]phenanthrolines has been prepared. The synthon acridones were achieved in very good yield by a one-pot reaction of 2-amino-5-chloro or 2′-chloro/flouro-substituted benzophenones with 1,2-cyclohexanedione in the presence of freshly prepared Eaton’s reagent (phosphorus pentoxide–methanesulfonic acid) without solvent, through Friedländer synthesis. Then these intermediates were reacted with 2-amino-3,5-dibromobenzaldehyde to afford 1,3-dibromo-10-chloro-8-aryl-6,7-dihydrodibenzo[b,j][1,10]phenanthroline. Also an one-pot reaction between 2 mol of 2-amino-5-chloro aryl benzophenones with 1 mol of 1,2-cyclohexanedione to get 3,10-dichloro-5,8-diaryl-6,7-dihydrodibenzo[b,j][1,10]phenanthroline has also been reported. The newly synthesized structures of the compounds were deduced by spectroscopic techniques.

A Green, Expeditious, One-Pot Synthesis of 3, 4-Dihydropyrimidin-2(1H)-ones Using a Mixture of Phosphorus Pentoxide-Methanesulfonic Acid at Ambient Temperature

An expeditious, one-pot method for the synthesis of 3,4-dihydropyrimidin-2(1H)-ones using a mixture of phosphorus pentoxide-methanesulfonic acid (Eaton's reagent) at room temperature under solvent-free conditions is described. The salient features of this method include short reaction time, green aspects, high yields, and simple procedure.

N, N′-Bis-(1 H-benzimidazol-2-yl)-isophthalamide as an additive in sulfonated polymer membranes for direct methanol fuel cells

N, N′-Bis-(1 H-benzimidazol-2-yl)-isophthalamide (BBImIP) has been synthesized using phosphorus pentoxide-methanesulfonic acid (PPMA) as a solvent and dehydrating agent and investigated as an additive in both sulfonated polysulfone (SPSf) membranes (up to 4.0 wt.% BBImIP) and sulfonated poly(ether ether ketone) membranes (up to 3.0 wt.% BBImIP). The SPSf/BBImIP blend membranes have been characterized by ion-exchange capacity and proton conductivity measurements as well as single cell and methanol crossover measurements in direct methanol fuel cells (DMFCs). Although the presence of BBImIP in the SPSf/BBImIP blend membranes lowers proton conductivity and cell performance compared to that of plain SPSf, it reduces methanol crossover significantly. On the other hand, the sulfonated poly(ether ether ketone) (SPEEK)/BBImIP blend membranes show cell performance comparable to or better than that of plain SPEEK membrane with reduced methanol crossover.

Sulfonated polysulfone with 1,3-1 H-dibenzimidazole-benzene additive as a membrane for direct methanol fuel cells

1,3-1 H-Dibenzimidazole-benzene (DBImBenzene) has been synthesized using phosphorus pentoxide-methanesulfonic acid (PPMA) as a solvent and dehydration agent and investigated as an additive (up to 2.0 wt.%) in sulfonated polysulfone (SPSf) membranes to promote proton conduction via acid–base interactions. The SPSf/DBImBenzene blend membranes with various DBImBenzene contents (0–2.0 wt.%) have been prepared and characterized by proton conductivity measurement and electrochemical polarization and methanol crossover measurements in direct methanol fuel cells (DMFCs). The blend membranes with DBImBenzene content of 0.5 and 1.0 wt.% show higher proton conductivities (3.4 and 2.9 × 10 −4 S/cm, respectively) than plain SPSf (2.4 × 10 −4 S/cm) even though the blend membranes have lower ion exchange capacity (0.81 and 0.75 mequiv./g, respectively) than plain SPSf (0.86 mequiv./g). The blend membranes exhibit better electrochemical performance in DMFC than plain SPSf membrane due to an enhancement in proton conductivity through acid–base interactions and lower methanol crossover.

Synthesis of novel sulfonated polybenzimidazole and preparation of cross-linked membranes for fuel cell application

A novel sulfonated polybenzimidazole, sulfonated poly[2,2′-(p-oxydiphenylene)-5,5′-bibenzimidazole] (SOPBI), was successfully prepared by post-sulfonation reaction of the parent polymer, poly[2,2′-(p-oxydiphenylene)-5,5′-bibenzimidazole] (OPBI), using concentrated and fuming sulfuric acid as the sulfonating reagent at 80°C, and the degree of sulfonation (DS) could be regulated by controlling the reaction conditions. No significant polymer degradation was observed in the post-sulfonation processes. Direct polymerization of 4,4′-dicarboxydiphenyl ether-2,2′-disulfonic acid disodium salt (DCDPEDS) and 3,3′-diaminobenzidine (DABz), however, resulted in insoluble gels either in polyphosphoric acid (PPA) or in phosphorus pentoxide/methanesulfonic acid (PPMA) in a ratio of 1:10 by weight reaction medium. The SOPBIs prepared by the post-sulfonation method showed good solubility in dimethyl sulfoxide (DMSO), high thermal stability, good film forming ability and excellent mechanical properties. Cross-linked SOPBI membranes were successfully prepared by thermal treatment of phosphoric acid-doped SOPBI membranes at 180°C in vacuo for 20h and the resulting cross-linked membranes showed much improved water stability and radical oxidative stability in comparison with the corresponding uncross-linked ones, while the proton conductivity did not change largely. Highly proton conductive (150mScm−1, 120°C in water) and water stable SOPBI membrane was developed.

P2O5—MsOH Mediated Regioselective Diaroylation of 2,2′‐Dimethoxy‐1,1′‐binaphthyl.

Abstract Phosphorus pentoxide–methanesulfonic acid (P2O5–MsOH) mediated electrophilic aromatic substitution diaroylation of 2,2′‐dimethoxy‐1,1′‐binaphthyl (1) with several aromatic carboxylic acids (3) proceeds to afford 6,6′‐diaroylated adducts (4) as single regioisomers.

Synthesis of a new sulfonated monomer for poly(aryl ether)s

AbstractA new sulfonated monomer suitable for polyarylether synthesis was made. 1,1'‐(p‐Phenylenedioxy)bis[4‐(4‐fluorobenzoyl)]benzene was prepared from phosphorus pentoxide/methanesulfonic acid (PPMA), 1,4‐diphenoxybenzene, and p‐fluorobenzoic acid in good yield. This compound was selectively monosulfonated on the most activated ring with fuming sulfuric acid and isolated as the sodium salt. Poly(aryl ethers) made from this monomer may find use as proton exchange membranes. © 2005 Wiley Periodicals, Inc. Heteroatom Chem 16:553–556, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20137

P2O5–MsOH Mediated Regioselective Diaroylation of 2,2′‐Dimethoxy‐1,1′‐binaphthyl

Phosphorus pentoxide–methanesulfonic acid (P2O5–MsOH) mediated electrophilic aromatic substitution diaroylation of 2,2′‐dimethoxy‐1,1′‐binaphthyl (1) with several aromatic carboxylic acids (3) proceeds to afford 6,6′‐diaroylated adducts (4) as single regioisomers.

Improved syntheses of poly(oxy-1,3-phenylenecarbonyl-1,4-phenylene) and related poly(ether–ketones) using polyphosphoric acid/P 2O 5 as polymerization medium

Based on the model-compound studies, the composition of polyphosphoric acid (PPA)/P 2O 5 mixture as an effective catalytic/dehydrative medium for the preparation of poly(ether–ketones) was optimized. Thus, with the optimal weight ratio of 4:1 (PPA:P 2O 5), the electrophilic substitution polycondensation of 3-phenoxybenzoic acid and related AB monomers was substantially promoted at 130 °C to yield the subject polymer abbreviated as mPEK and related poly(ether–ketones) with significantly higher molecular weights. In the cases where the polymerization systems were completely homogeneous, the ensuing polycondensation was rapid and yielded high molecular weight polymers (e.g. mPEK [η]=2.10 dl/ g ) at 130 °C within 30 min., as compared to PPMA (phosphorus pentoxide/methanesulfonic acid) method which gave only moderate molecular weight polymers, e.g. mPEK ([η]=0.64 dl/ g). In some cases, where the monomers and PPA/P 2O 5 were not fully compatible, polycondensation did proceed and reasonable molecular weight range ([η]=0.69–0.76 dl/ g) could be achieved. However, the complete incompatibility between the poly(ether–sulfone) and PPA/P 2O 5 medium precluded the successful polymerization of 4-phenoxybenzenesulfonic acid.

Synthesis, modification, and characterization of hyperbranched poly(ether ketones)

This report presents the synthesis and chemical modification of hyperbranched poly(ether ketones). The polymer was conveniently prepared by direct polycondensation of an AB 2 monomer, 3,5-diphenoxybenzoic acid, using phosphorus pentoxide/methanesulfonic acid (PPMA) as the condensing agent and solvent. The hyperbranched poly(ether ketone) could be modified via the electrophilic aromatic substitution of the active phenoxy groups at the chain ends with a variety of carboxylic acids. The thermal properties of the hyperbranched poly(ether ketones) depend heavily on the nature of the chain end, with glass transition temperature ranging from −24°C to 180°C. Moreover, the length of the terminal alkyl groups significantly influences the solubility of the hyperbranched poly(ether ketones). By varying the chain ends, hyperbranched poly(ether ketones) soluble in either a polar or nonpolar solvent could be obtained.

Structural requirements for decarbonylative α,α-diarylation reaction of 2-methoxyalkanoic acids in phosphorus pentoxide-methanesulfonic acid mixture yielding 1,1-diarylalkane homologs

2-Methoxyalkanoic acids were found to undergo consecutive decarbonylative α,α-diarylation in P 2O 5-MsOH instead of Friedel-Crafts type arylation on the carbonyl carbon. The influence of the substituents of the arenes and the carboxylic acids in this reaction was elucidated based on the reaction yields. The reaction behavior was found to be primarily governed by the electron-withdrawing/releasing property of the α-substituents on the carboxylic acids as well as the positive species-accepting ability of the arenes. The steric hindrance was shown to participate in determining the reaction feasibility as a secondary factor.

ChemInform Abstract: Ring Construction of Several Heterocycles with Phosphorus Pentoxide‐ Methanesulfonic Acid (PPMA).

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Ring Construction of Several Heterocycles with Phosphorus Pentoxide-Methanesulfonic Acid (PPMA)

Ring Construction of Several Heterocycles with Phosphorus Pentoxide-Methanesulfonic Acid (PPMA)

Synthesis and characterization of poly(1-benzoylthiosemicarbazide) and poly(1,3,4-thiadiazole amine) from 2-(p-aminophenyl)-1,3,4-oxadiazoline-5-thione via ring-opening process

A novel thermally stable and semiconducting polyheterocycle, poly(1,3,4-thiadiazole amine), was synthesized from 2-(p-aminophenyl)-1,3,4-oxadiazoline-5-thione via ring-opening. The polymer is a new class of ordered alternating copoly(aniline) containing 1,3,4-thiadiazole heterocyclic units. An investigation of the reaction of 2-phenyl-1,3,4-oxadiazoline-5-thione with aniline was conducted as a model reaction for the polymerization, and poly(phosphoric acid) (PPA) and phosphorus pentoxide/methanesulfonic acid (PPMA) were found to be favorable both as condensing agent and solvent for the formation of 2-anilino-5-phenyl-1,3,4-thiadiazole as a model compound. The polymerization was carried out both by two-step procedure that included ring-opening self-polyaddition giving poly(1-benzoylthiosemicarbazide), followed by cyclodehydration to poly(1,3,4-thiadiazole amine), and by a one-step procedure including cyclodehydration in situ. The poly(1-benzoylthiosemicarbazide) which was formed in the first step in m-cresol had reduced viscosities up to 0,42 dL·g−1, and it was converted to poly(1,3,4-thiadiazole amine) by treating in PPA or PPMA. Poly(1,3,4-thiadiazole amine) having reduced viscosities up to 0,25 dL·g−1 was also synthesized by the direct one-step polymerization in PPA or PPMA. The polymer is highly thermally stable and exhibited no weight loss up to 350°C under nitrogen. Its electric conductivity was less than 10−10 S·cm−1 at ambient temperature, but markedly increased to 2,9·10−7 S·cm−1 upon doping with iodine.

Synthesis of poly(chalcone)s by polycondensation of aromatic dialdehydes with aromatic diacetyl compounds

AbstractPoly(chalcone)s were prepared by polycondensation of aromatic dialdehydes with aromatic diacetyl compounds in methanesulfonic acid (MSA) or phosphorus pentoxide/methanesulfonic acid (PPMA). Polycondensations proceed smoothly at room temperature and produced poly(chalcone)s with inherent viscosities up to 0,97 dL · g−1. The reaction of acetophenone with aromatic aldehydes in MSA or PPMA was studied in detail to demonstrate the feasibility for polymer formation. Poly(chalcone)s are only soluble in concentrated sulfuric acid and methanesulfonic acid at room temperature. Thermogravimetry of poly(chalcone)s showed 10% weight loss around 380 and 420°C in air and under nitrogen, respectively.

Synthesis of aromatic poly(thioether ketone)

AbstractAromatic poly(thioether ketone)s were prepared by the direct polycondensation of aromatic dicarboxylic acids with aryl compounds containing ether or sulfide structures using phosphorus pentoxide/methanesulfonic acid (PPMA) as a condensing agent and solvent. Polycondensation proceeded smoothly and produced aromatic poly(thioether ketone)s with inherent viscosities up to 0.73 dL/g. The synthesis of substituted aryl ketones by the reaction of substituted benzoic acids with aryl compounds in PMMA was studied in detail to demonstrate the feasibility of the reaction for polymer formation. The thermogravimetry of the aromatic poly(thioether ketone)s showed a 10% weight loss in air and nitrogen at around 450 and 460°C, respectively. © 1992 John Wiley & Sons, Inc.

Synthesis of aryl-substituted sulfonium salts by the phosphorus pentoxide-methanesulfonic acid promoted condensation of sulfoxides with aromatic compounds

Resultats presentes dans un tableau, apres synthese a 20-40°C pendant une heure d'un melange du dialkyl ou diaryl sulfoxyde en presence de P 2 O 5 /MSA. Tous les sels de sulfonium ont ete caracterises par RMN 1 H et 13 C, spectres UV, points de fusion et analyse elementaire

Synthesis of poly(benzoxazinone)s by direct polycondensation of dicarboxylic acids with bis(anthranilic acid)s

AbstractA convenient method for the synthesis of poly(benzoxazinone)s of high molecular weights has been developed. These polymers were prepared readily by direct polycondensation of aromatic dicarboxylic acids containing phenyl ether structures with bis(anthranilic acid)s using phosphorus pentoxide/methanesulfonic acid (PPMA) as a condensing agent and solvent. Polycondensations proceeded smoothly and were completed within several hours at 140°C to produce poly(benzoxazinone)s with inherent viscosities up to 2.6 dL/g. The synthesis of 2‐substituted benzoxazinones by the reaction of aromatic carboxylic acids or dicarboxylic acid with anthranilic acid in PPMA was studied in detail to demonstrate the feasibility of the reaction for polymer formation. The thermogravimetry of the aromatic poly(benzoxazinone)s showed 10% weight loss in air and nitrogen around at 440 and 460°C, respectively.