Addition Of P-toluenesulfonic Acid Research Articles

Curing Behavior of Sucrose with p-Toluenesulfonic Acid.

With respect to the fossil resources shortage, the development of bio-based wood adhesives is an important research topic in wood science. There has been research on using sucrose for bio-based adhesives. However, a high acid catalyst content and a high hot-pressing temperature are required when manufacturing particleboards. In this study, to explore the possibility of p-toluenesulfonic acid (PTSA) as a promising acid catalyst for sucrose-based adhesives, the curing behavior of sucrose with PTSA (Suc-PTSA) was clarified. The thermal analysis results showed that the thermal properties of sucrose decreased significantly with the addition of PTSA. Based on the results of the insoluble matter rate, the optimal mixture ratio and heating conditions were determined to be 95:5 and 180 °C for 10 min, respectively. According to the results of FT-IR, the heat-treated Suc-PTSA contained furan compounds. In the context of the dynamic viscoelasticity, the onset temperature at which the storage modulus (E') begins to rise was significantly lower than those of the other sucrose-based adhesives. PTSA has the potential to cure sucrose more efficiently and at lower temperatures than previous sucrose-based adhesives, making it a promising acid catalyst for sucrose.

Facile fabrication of mechanically-strong and flame retardant alginate/clay aerogels

Mechanically-strong sodium alginate/clay aerogel were fabricated by addition of p-toluenesulfonic acid using a freeze-drying method. The adjusting of pH from 8 (the control) to 6, on the one hand lead to the crosslinking of alginate, on the other hand thickened the clay sol. The compressive modulus of A5C5 aerogel significantly increased from 6.0 ± 0.4 MPa (pH = 8) to 17 ± 3 MPa (pH = 6). The morphological structure characterization showed that the microstructure of aerogels changed from layered to network with decreasing pH value, with cell size ranging from 4 to 8 μm. The rheological behavior showed that the addition of p-toluenesulfonic acid would significantly improve the viscosity of the precursors at low frequency. The combustion tests indicated that all the alginate/clay aerogels possess excellent flame retardancy. The addition of p-toluenesulfonic acid further slightly increased the thermal stability and fire safety of the material. This facile preparation procedure of strengthened polymer/clay aerogel via adjusting pH is promising and can be spread.

Analysis of Models Predicting Morphology Transitions in Reactive Twin-Screw Extrusion of Bio-Based Polyester/Polyamide Blends

Abstract Immiscible PLA/PA11 of 80/20 and 50/50 wt% were compatibilized through addition of p-toluenesulfonic acid (TsOH) catalyst in reactive ultra-high speed twin-screw extrusion. Two mixing screw designs were compared for their ability to disperse the PA11 droplets in the PLA matrix as a function of screw speed up to 2000 rpm. The size and polydispersity of droplets of dispersed PA11 decreased when a high shear (HS) screw was used, whereas broad droplet size distribution was produced in the low shear (LS) screw. Two models predicting the droplet size dependence on shear rate, viscosity ratio and interfacial tension were fit to the experimental data. The Serpe model including volume fraction effects produced a better fit compared to the Wu model, which does not include volume fraction effects. Mechanical testing indicated that the compatibility of PLA/PA11 blends was improved through addition of TsOH catalyst for 50/50 wt% blends due to ester – amide exchange reactions at the interfaces in the immiscible PLA and PA11 phases. The enhancement of ductility was greater after processing with the LS screw configuration than the HS screw configuration. The inferior properties after high shear mixing were likely due to molecular weight degradation during processing. While the aggressive shear in the HS screw design resulted in fine dispersion, care should be taken to minimize degradation, especially for shear sensitive polymers.

ChemInform Abstract: Lipase‐Catalyzed Domino Michael—Aldol Reaction of 2‐Methyl‐1,3‐cycloalkanedione and Methyl Vinyl Ketone for the Synthesis of Bicyclic Compounds.

ABSTRACTSynthesis of bicyclic compounds was achieved via a lipase-catalyzed, stereoselective, domino Michael–aldol reaction of 2-methyl-1,3-cycloalkanedione and methyl vinyl ketone. Appropriate reaction conditions, including the type of enzyme, solvent, and temperature, were determined. In addition, the effects of solvent polarity and addtives were investigated. The reaction proceeded in the presence of lipase AS in a solution of 20% acetone in dimethylsulfoxide (DMSO) at 10 °C for 8 days, followed by the addition of p-toluenesulfonic acid (TsOH) to afford bicyclic compounds in 51–83% yields with moderate stereoselectivity. Although this domino Michael–aldol reaction showed only moderate stereoselectivity, even with the acid-supported enhancement of the reaction, these results represent potential new applications for lipase.

Lipase-catalyzed domino Michael–aldol reaction of 2-methyl-1,3-cycloalkanedione and methyl vinyl ketone for the synthesis of bicyclic compounds

ABSTRACTSynthesis of bicyclic compounds was achieved via a lipase-catalyzed, stereoselective, domino Michael–aldol reaction of 2-methyl-1,3-cycloalkanedione and methyl vinyl ketone. Appropriate reaction conditions, including the type of enzyme, solvent, and temperature, were determined. In addition, the effects of solvent polarity and addtives were investigated. The reaction proceeded in the presence of lipase AS in a solution of 20% acetone in dimethylsulfoxide (DMSO) at 10 °C for 8 days, followed by the addition of p-toluenesulfonic acid (TsOH) to afford bicyclic compounds in 51–83% yields with moderate stereoselectivity. Although this domino Michael–aldol reaction showed only moderate stereoselectivity, even with the acid-supported enhancement of the reaction, these results represent potential new applications for lipase.

ChemInform Abstract: Triple Role of Phenylselenonyl Group Enabled a One‐Pot Synthesis of 1,3‐Oxazinan‐2‐ones from α‐Isocyanoacetates, Phenyl Vinyl Selenones, and Water.

Reaction of α-substituted α-isocyanoacetates with phenyl vinyl selenones in the presence of a catalytic amount of base (DBU or Et3N, 0.05–0.1 equiv) followed by addition of p-toluenesulfonic acid (PTSA, 0.1–0.2 equiv) afforded 4,4,5-trisubstituted 1,3-oxazinan-2-ones in good to excellent yields. Enantiomerically enriched heterocycles can also be prepared using a Cinchona alkaloid-derived bifunctional organocatalyst for the Michael addition step. The phenylselenonyl group served as an activator for the Michael addition, a leaving group and a latent oxidant in this integrated reaction sequence.

Triple role of phenylselenonyl group enabled a one-pot synthesis of 1,3-oxazinan-2-ones from α-isocyanoacetates, phenyl vinyl selenones, and water.

Reaction of α-substituted α-isocyanoacetates with phenyl vinyl selenones in the presence of a catalytic amount of base (DBU or Et3N, 0.05-0.1 equiv) followed by addition of p-toluenesulfonic acid (PTSA, 0.1-0.2 equiv) afforded 4,4,5-trisubstituted 1,3-oxazinan-2-ones in good to excellent yields. Enantiomerically enriched heterocycles can also be prepared using a Cinchona alkaloid-derived bifunctional organocatalyst for the Michael addition step. The phenylselenonyl group served as an activator for the Michael addition, a leaving group and a latent oxidant in this integrated reaction sequence.

9,9-Diaryl-4,5-diazafluorene-based Cardo polymer; Synthesis and characteristic properties

To open out new aspects of 9,9-diarylfluorene (DAF)-based polymers with high performances, 9,9-(4-hydroxyphenyl)-4,5-diazafluorene (N-BPF) was designed as a new cardo structure and the properties of poly(ether ketone)s (N-PEKs) containing N-BPF skeletons were examined in detail. N-PEKs were synthesized in high yields via polycondensation of N-BPF with difluoroarenes. N-PEKs showed cardo polymer-specific properties such as high thermal stability and high solubility in organic solvents. The addition of p-toluenesulfonic acid (TsOH) to N-PEK resulted in the formation of network polymer based on interchain hydrogen bonds. It turned out that the films of network polymer are flexible and transparent and exhibit high refractive index and low birefringence. The effects of feed ratio of TsOH to N-PEK were also evaluated on the mechanical properties of network polymer. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 4541–4549

Highly Conductive Polypyrrole/γ-Fe2O3 Nanospheres with Good Magnetic Properties Obtained through an Improved Chemical One-Step Method

An improved chemical one-step method (ICOSM) was used to prepare highly conductive and magnetic polypyrrole/γ-Fe2O3 (PPy/γ-Fe2O3) nanospheres ∼80 nm in diameter. In the reaction process involved, FeCl3 acts as an oxidant for the polymerization of pyrrole and as a source of FeIII for the formation of γ-Fe2O3, which also requires the initial presence of FeII, provided by the addition of FeCl2. The method differs from the previous chemical one-step method (COSM) through the addition of p-toluenesulfonic acid (p-TSA) as the dopant after addition of the FeCl3 solution was finished. The conductive and magnetic properties of PPy/γ-Fe2O3 nanospheres increased and reached maximum values simultaneously with increasing amounts of FeCl2, contrary to the result observed in the previous COSM. The resulting electromagnetic PPy/γ-Fe2O3 nanospheres show maximum conductivity of 64.4 S/cm and saturation magnetization of 4.85 A m2/kg. The p-TSA dopant plays a critical role in the formation of PPy/γ-Fe2O3 nanospheres.

Acid-Sensitive Pt(II) 2,6-Di(pyridin-2-yl)pyrimidin-4(1H)-one Complexes

Three Pt(II) 2,6-di(pyridin-2-yl)pyrimidin-4(1H)-one complexes (2-4) with chloride or 4-ethynyltolyl ancillary ligands were synthesized and characterized. The photophysical properties of 2-4 were investigated in different solvents and at different acid concentrations. Their electronic absorption and emission responses at various acid concentrations were compared to those of 5. 2-4 all exhibit a broad charge-transfer band in their electronic absorption spectra from 380 to 500 nm and emit at about 560 nm in acetonitrile at room temperature, presumably ascribed to the triplet metal-to-ligand charge transfer ((3)MLCT) state. All of them exhibit broad and relatively strong triplet transient absorption in the visible to the near-IR region (450-820 nm). Upon addition of p-toluenesulfonic acid, the original charge-transfer band intensity decreases, accompanied by the increase of the absorption in the 350-400 nm region in their electronic absorption spectra. Meanwhile, the (3)MLCT emission is quenched, and the triplet transient absorption intensity decreases. The changes in electronic absorption, emission, and the transient absorption spectra are reversible upon the addition of base, that is, triethylamine. The reversible acid sensitivity is caused by the protonation and deprotonation of the carbonyl oxygen on the terdentate ligand. Therefore, these platinum complexes could be potential chromogenic and luminescent sensors for acids.

Mononuclear oxovanadium complexes of tris(2-pyridylmethyl)amine

Mononuclear oxovanadium(IV) and dioxovanadium(V) complexes of tris(2-pyridylmethyl)amine (tpa) have been prepared for the first time. Crystal structure determinations of three oxovanadium(IV) complexes, [VO(SO4)(tpa)], [VOCl(tpa)]PF6, or [VOBr(tpa)]PF6, and a dioxovanadium(v) complex [V(O)2(tpa)]PF6 disclosed that the tertiary nitrogen of the tpa ligand always occupies the trans-to-oxo site. The structures of an oxo-peroxo complex [VO(O2)(tpa)]Cl that was prepared previously and of a mu-oxo vanadium(III) complex [{VCl(tpa)}2(mu-O)](PF6)2 have also been determined. The tertiary nitrogen is located at a trans site to the peroxo and chloride ligands, respectively. The total sums of the four V-N bond lengths from the tpa ligand are remarkably similar among the six complexes, indicating that the vanadium oxidation states become less influential in tpa bonding due primarily to the coordination of electron-donating oxo ligand(s). Absorption spectra of [VOCl(tpa)]+ in acetonitrile showed a significant change upon addition of p-toluenesulfonic acid and HClO4, but not on addition of benzoic acid. Protonation at the oxo ligand by the former two acids is suggested. Cyclic voltammetric studies in acetonitrile verified the proton-coupled redox behavior of the V(III)/V(IV) process involving the oxo ligand for the first time. From the dependence of the added p-toluenesulfonic acid to the CV, redox potentials for the following species have been estimated: [V(IV)OCl(tpa)]+/[V(III)OCl(tpa)](E1/2=-1.59 V vs. Fc+/Fc), [V(IV)(OH)Cl(tpa)]2+/[V(III)(OH)Cl(tpa)]+(Epc=-1.34 V), [V(IV)(OH2)Cl(tpa)]3+/[V(III)(OH2)Cl(tpa)]2+(Epa=-0.49 V), and [V(IV)Cl2(tpa)]2+/[V(III)Cl2(tpa)]+(E1/2=-0.89 V). The reduction of [V(V)(O)2(tpa)]+ in 0.05 M [(n-Bu)4N]PF6 acetonitrile showed a major irreversible reduction wave V(V)/(IV) at -1.48 V. The metal reduction potentials of the oxovanadium(IV) and dioxovanadium(V) species are very close, reinforcing the significant influence of the oxo ligand(s).

Palladium catalyzed oxidation of monoterpenes: multistep electron transfer catalytic systems Pd(OAc) 2/benzoquinone/M(OAc) 2 (M=Cu, Co or Mn) for the allylic oxidation of limonene with dioxygen

Oxidation of limonene ( 1) with dioxygen in acetic acid solutions containing catalytic amounts of Pd(OAc) 2, benzoquinone and M(OAc) 2 (M=Cu, Co or Mn) has been developed. Main reaction products are three isomeric allylic acetates, i.e., trans-2-acetoxy- p-mentha-1(7),8-diene ( 2), perilla acetate ( 3) and trans-carveyl acetate ( 4). A good control of chemo- and regioselectivities has been achieved through the addition of p-toluenesulfonic acid. The systems with Cu(OAc) 2 have shown the most promising results. Acetate 2, which has a mild scent of flower or fruit and can be useful as a component of synthetic fragrances, has been obtained in higher than 90% chemoselectivity at 90–95% limonene conversions.

Electrochemical studies of acid-promoted disproportionation of nitroxyl radical

The acid-promoted disproportionation of 2,2,6,6-tetramethylpiperidinyl-1-oxyl (TEMPO) was studied in order to elucidate the recycling process of the catalytic oxidation of alcohol by nitroxides. Potentiometry, cyclic and hydrodynamic voltammetries with a rotating disk electrode (RDE) have been used to investigate the formation of a nitrosonium cation and a hydroxylamine by disproportionation of nitroxides in acetonitrile. The addition of p-toluenesulfonic acid caused the rest potential of the TEMPO/nitrosonium cation couple to shift in a more positive direction and decreased the peak current in the cyclic voltammograms. The subsequent addition of 2,6-lutidine as a Lewis base made the rest potential and the peak current recover. These phenomena corresponded to the recycling of the catalytic process by TEMPO in a basic aprotic solution.

Studies on the optical properties and stability in dc: Conductivity of PTSA-I 2 doped poly-4-vinyl pyridine

The optical and electrical properties of high molecular weight ( M ̄ v =14.8×10 5) poly(4vinylpyridine) (P4VP) doped with PTSA/I 2 have been studied. The polymer has been synthesized by bulk polymerization technique and characterized by viscometry, IR spectra and DSC studies. P-toluene sulfonic acid (PTSA) is used as counter ion with strong electron acceptor iodine(I 2) dopant. It acts as a good stabilizer and a plasticizer. The formation of charge transfer complex between P4VP/PTSA/I 2 has been confirmed by UV–VIS absorption spectra in the wavelength range 190–700 nm. The absorption coefficient, Energy band gap and activation energy are calculated. The charge transfer complex (CTC) formed between P4VP and iodine shows good stability by the addition of PTSA. dc conductivity of these films has been studied as a function of temperature and conduction mechanisms have been discussed by motts approach. The stability in dc conductivity of the complex at high temperature is mainly due to the reabsorption of I 2 by PTSA.

Phosphines versus phosphinites as ligands in the rhodium catalyzed asymmetric hydrogenation of imines: a systematic study

The asymmetric hydrogenation of N-(1-phenylethylidene)benzylamine with a range of rhodium(I)-diphosphine and diphosphinite catalysts is studied. The reaction is strongly sensitive to the size of the metal chelate. Complexes based on five- and six-membered chelates or electron-rich alkylphosphines gave poor or moderate conversions. The reactivity of diphosphine catalysts could be increased by the addition of p-toluenesulfonic acid. Unexpectedly, Rh-complexes based on chiral diphosphinites and a diphosphite also rapidly converted the substrate to the desired amine. Highest efficiency was observed with a rhodium(I) complex with ( R, R)-1,2-cyclohexanol-bisdiphenylphosphinite [( R, R)-bdpch] as chiral ligand. Without any additive complete hydrogenation of the imine was achieved within 5 h. The product was produced in an enantioselectivity of 71%.

Controlled Continuous Production of Conducting Polypyrrole Tapes I: Process Control Development

A common method for the synthesis of conducting polypyrrole involves the use of potentiostatic or galvanostatic deposition. The electrical and mechanical properties of the polymer resulting from these synthesis techniques are known to be highly dependent on a number of factors. These factors include the reactant and electrolyte concentrations and other conditions, such as pH. During batch synthesis these parameters have been observed to vary, so that the electrodeposited polypyrrole film is affected by continually changing chemical environments. As a result, polymeric material with different properties is deposited on top of the polymer formed earlier during synthesis. This problem is further exacerbated when polypyrrole is synthesized on a continuous basis using a rotating anode electrode. In order to avoid these effects a process control system has been developed to monitor and control these critical parameters for both batch and continuous electrochemical synthesis of polypyrrole in water. The system is based on monitoring dopant concentration, monomer concentration and pH using flow-through UV-visible spectroscopy, electrochemical detection by pulsed potential rotating disk electrode and a pH meter respectively. Control was achieved by using a closed loop PID (proportional, integral, derivative) controller for pH and a closed loop on/off controller for monomer concentration. The control of dopant concentration was found to be unnecessary when pH control was employed as the addition of p-toluenesulfonic acid to control pH compensated for dopant depletion.

Preparation, Structure, and Properties of Bis(μ-oxo)dirhenium(III,IV) and -dirhenium(IV) Complexes of Tris(2-pyridylmethyl)amine and Its (6-Methyl-2-pyridyl)methyl Derivatives

A series of bis(&mgr;-oxo)dirhenium complexes, [Re(2)(&mgr;-O)(2)(L)(2)](PF(6))(n)() (L = tris(2-pyridylmethyl)amine (tpa), n = 3 (1), n = 4 (1a); L = ((6-methyl-2-pyridyl)methyl)bis(2-pyridylmethyl)amine (Metpa), n = 3 (2), n = 4 (2a); bis((6-methyl-2-pyridyl)methyl)(2-pyridylmethyl)amine (Me(2)tpa), n = 3 (3), n = 4 (3a)), have been prepared and characterized by several physical methods. X-ray crystallographic studies for 2, 2a.2CH(3)CN.2H(2)O (2a'), and 3a' (ReO(4)(-) salt), include the first structural determinations of (i) the bis(&mgr;-oxo)-Re(III)Re(IV) complex (2) and (ii) the pair of Re(III)Re(IV) and Re(IV)(2) complexes (2 and 2a'). All the complexes have a centrosymmetric structure, suggesting that the mixed-valence state 2 is of structurally delocalized type. The Re-Re distances for 2, 2a.2CH(3)CN.2H(2)O, and 3a' are 2.426(1), 2.368(1), and 2.383(1) Å, respectively, being consistent with the bond order of 2.5 (sigma(2)pi(2)delta(2)delta) for 2 and 3 (sigma(2)pi(2)delta(2)) for the others. Methyl substitution on the pyridyl moiety of the ligands has no significant influence to the overall structure. Cyclic voltammetry of 1 shows two reversible redox waves at -0.77 ((III,III)/(III,IV)) and 0.09 V ((III,IV)/(IV,IV)) vs Ag/AgCl in acetonitrile. The potentials are slightly more positive for 2 (-0.66 and 0.14 V) and 3(-0.64 and 0.20 V). No proton-coupled redox behavior was observed on addition of p-toluenesulfonic acid. Complexes, 1a, 2a, and 3a show a strong visible absorption band at 477 nm (epsilon, 9200 dm(3) mol(-)(1) cm(-)(1)), 482 (11200), and 485 (8700), respectively, which is assigned to the pi-pi transition within the Re(2)(&mgr;-O)(2) core. For the mixed-valence complexes 1, 2, and 3, a strong band is observed in the longer wavelength region (556-572 nm). Crystal data: 2, monoclinic, space group C2/c (No.15), a = 11.799(2) Å, b = 19.457(3) Å, c = 21.742(4) Å, beta = 98.97(1) degrees, Z = 4; 2a', triclinic, space group P&onemacr; (No. 2), a = 13.151(3) Å, b = 13.535(2) Å, c = 10.243(3) Å, alpha = 104.37(2) degrees, beta = 109.02(2) degrees, gamma = 106.87(1) degrees, Z = 1; 3a', monoclinic, space group P2(1)/n (No. 14), a = 13.384(3) Å, b = 14.243(2) Å, c = 13.215(6) Å, beta = 106.88(2) degrees, Z = 2.

Synthesis of a Key Intermediate for D-Biotin via 1,3-Cycloaddition of a Thiocarbonyl Ylide and Sila-Pummerer Rearrangement

An efficient preparation of a d-biotin intermediate, (±)-(3aα,4α,6aα)-1,3-dibenzyl-3a,4,6,6a-tetrahydro-4-hydroxy-1H-thieno[3,4-d]imidazol-2(3H)-one was accomplished by use of 1,3-cycloaddition of a thiocarbonyl ylide, Curtius rearrangement and sila-Pummerer rearrangement. Addition of p-toluenesulfonic acid was found to be effective to promote sila-Pummerer rearrangement of sterically unfavorable anti-2-trimethylsilyl sulfoxide

Influence of added salts and acids on the ionic hydrogenation of thiophenes

1. The ionic hydrogenation of thiophenes is greatly accelerated by a large excess of trifluoroacetic acid or small quantities of p-toluenesulfonic acid or neutral salts (lithium perchlorate and lithium tosylate). 2. In the hydrogenation of 2-ethylthiophene use of excess CF3COOH or addition of p-toluenesulfonic acid or LiClO4 not only accelerates the reaction but also increases the yield of 2-ethyltetrahydrothiophene.