4-acetoxybenzoic Acid Research Articles

Synthesis of silsesquioxane-linked polyester with liquid crystalline backbone chain

A novel procedure for the synthesis of a 3D network polyester bearing silsesquioxane cores was executed to prepare the ternary silsesquioxane-linked copolyester BNH (BNH4 and BNH8) based on 4-acetoxy benzoic acid (ABA), 6-acetoxy-2-naphthoxylic acid (ANA), and a silsesquioxane-cored monomer (CSQ-AHA4 or CSQ-AHA8). The thermal data and phase behavior indicated that moderate crosslinking would reduce the stacking of the backbones, thereby enhancing the mobility of the backbone. However, greater crosslinking would limit the movement of the backbone, while the 3D cross-linked structure enhanced the structural stability of the phase region and the uniformity of the crystal size distribution. The loose fiber bundles showed that the participation of the 3D configuration and silsesquioxane increased the chain flexibility, and facilitated the formation of strong polyester ultrafine fibers. It was possible to improve the lateral mechanical properties of the oriented polyester materials, probably improving the mechanical properties aspect ratio of thin film materials.

Synthesis of stable fluorescent ethylene-vinyl acetate copolymers based on in-situ grafted rare-earth organic complexes and antioxidants through transesterification

The synthesis and application of rare earth organic complexes (REOCs) are gaining attention due to their advantages including low excitation thresholds and high luminescence efficiencies. However, their integration as functional fillers in polymer matrices is constrained by challenges related to poor dispersion and limited stability. This study introduces a novel method for synthesizing stable fluorescent polymers by co-grafting europium (Eu) complexes and the antioxidant 3,9-bis-{1,1-dimethyl-2[β-(3-tert-butyl-4-hydroxy-5-methylphenyl-)propionyloxy]ethyl}-2,4,8,10-tetraoxaspiro[5.5]-undecane (AO-80) onto an ethylene-vinyl acetate (EVA) matrix through an in-situ synchronous grafting strategy, aiming to address these dual challenges of poor dispersion and rapid aging. In this study, Eu complexes characterized by low excitation thresholds and high hexahydrate (EuCl3) and selected ligands - 1,10-phenanthroline (Phen), alpha-thienyl trifluoroacetone (HTTA), and 4-acetoxybenzoic acid (4-ABA). Through transesterifications, the Eu complexes were successfully grafted onto the EVA chain, achieving a uniform dispersion within the EVA matrix to form fluorescent polymers. Furthermore, the incorporation of antioxidant AO-80 as a radical scavenger can significantly mitigate fluorescence attenuation. Through detailed exploration of transesterifications under various conditions, optimal grafting rates of 11.34% for EVA with Eu complexes and 22.87% for EVA with AO-80 were achieved. The synthesized fluorescent polymers of EVA synchronously grafted with Eu complexes and AO-80 have been proven to obtain markedly improved fluorescence stability and aging resistance by outdoor aging tests. Our findings not only validate the in-situ reaction grafting method as an efficient strategy for producing polymer composites with excellent fluorescence stability but also pave the way for future research aimed at overcoming the limitations of REOCs in photovoltaic and agricultural applications.

From Solution Studies of Pharmaceuticals (Aspirin and Related Compounds) to the Thermodynamics of Aspirin-β-Cyclodextrin Interaction in water and N,N-Dimethylformamide.

The solution behavior of pharmaceuticals (acetylsalicylic acid, 4-acetoxybenzoic acid and 5-acetylsalicylic acid) in water and N,N-Dimethylformamide (DMF) at 298.15 K were investigated through solubility, conductance and calorimetric measurements. Taking into account the formation of ion pairs of these pharmaceuticals in water, the solution Gibbs energies of the dissociated electrolytes in this solvent were calculated. Thus, the solution thermodynamics of these compounds in water are reported using enthalpy data obtained by calorimetry. These pharmaceuticals undergo solvation when exposed to a saturated atmosphere of DMF. As the composition of the solid is not the same as that in solution, the Gibbs energy of the solutions of these compounds could not be obtained; only enthalpy data are reported. The thermodynamics of the interaction of acetylsalicylic acid (aspirin) with β-cyclodextrin in water and DMF is fully discussed, emphasizing the two different processes that take place in water at the two different pHs. In all cases, the favorable Gibbs energies for these processes are entropically controlled, mainly resulting from the higher dehydration/desolvation that the receptor undergoes upon interaction with the guest.

Reaction mechanism study on transesterification in synthesis of thermotropic liquid crystalline polymer catalyzed by zinc(II) carboxylate: A combination of DFT and kinetics analyses

A deep insight into the reaction mechanism is essential to control the polymerization process with the desired macromolecular structure for high-performance thermotropic liquid crystalline polymer. In this work, density functional theory (DFT) was used to investigate the catalytic polymerization mechanism for the synthesis of thermotropic liquid crystalline polymer catalyzed by zinc(II) carboxylate. The polymerization of 4-acetoxybenzoic acid was studied as a typical reaction. Based on DFT calculations, the rate-limiting step is located in the transesterification between phenol and anhydride acid. The energetically favored pathway was found with the free energy barrier of 51.84 kcal/mol in the presence of zinc acetate, which is significantly lower than the energy barrier without a catalyst. In addition, the effects of the carboxylate group of zinc(II) carboxylate on the catalytic efficiency were revealed by DFT calculations and experiments. Compared with zinc acetate, zinc pivalate has a higher catalytic activity with the rate constant of 1.69 × 10-2 min−1∙M−1 fitted with a second-order reaction model. The HOMO-LUMO gap of zinc pivalate was the smallest among the chosen catalyst, indicating that the chemical activity was strengthened by the methyl substituted. Furthermore, due to the enhanced orbital interactions and the decreased distortion energy in the transition state using zinc pivalate, the energy barrier of the rate-limiting step decreased to 51.36 kcal/mol. These results provide valuable guidance for modeling the catalytic mechanism in aromatic polyester systems.

Co-ordination behaviour of hydrazine and isomers of acetoxy benzoic acids with transition metal ions

ABSTRACT. New hydrazine complexes of some divalent transition metal ions of formulae, [M{(2-ab)2(N2H4)}].3H2O, [M{(3-ab)2(N2H4)}].3H2O and [M{(4-ab)2(N2H4)2}].2H2O where M = Co, Ni, Zn and Cd; 2-abH = 2-acetoxy benzoic acid, 3-abH = 3-acetoxy benzoic acid and 4-abH = 4-acetoxy benzoic acid were prepared using their respective metal nitrates and hydrazine hydrate at pH 6 and 5, respectively, and characterized by elemental analysis, IR and UV-reflectance spectroscopic techniques, thermo analytical technique, powder XRD, SEM-EDX and magnetic susceptibility measurements. All the transition metal complexes were sparingly soluble in water. The IR spectra of complexes showed N-N absorptions of hydrazine in the range of 964-988 cm-1 substantiating the bidentate bridging coordination of hydrazine. They showed endothermic decomposition in the range of 67-100 °C, exothermic dehydrazination in the range, 210-281 °C and an oxidative decomposition between 350 and 490 °C to form their respective metal oxides. The electronic spectral and magnetic susceptibility data could substantiate the distorted octahedral geometry of nickel and cobalt complexes and the XRD pattern indicates the existence of isomorphism. Crystals of [Cd(H2O)3((C6H4(4-OH)(COO))2].H2O obtained as by-product, was also characterized using single crystal XRD, IR and thermal studies.
 
 KEY WORDS: Acetoxy benzoic acids, Hydrazine, Thermal analysis, Single crystal XRD
 
 Bull. Chem. Soc. Ethiop. 2021, 35(2), 337-350. 
 DOI: https://dx.doi.org/10.4314/bcse.v35i2.9

Effect of an allostatic modulator on stress blood indicators and meat quality of commercial young bulls in Mexico

To assess the effect of an allostatic modulator (AM) on stress blood indicators and meat quality traits, the feed of 80 non-castrated 18–20month-old bulls was supplemented with 10g/day of an AM for 30days before slaughter. Another 80 bulls served as control animals. The AM was comprised of ascorbic acid, acetoxybenzoic acid and sodium and potassium chloride. Blood samples were taken at slaughter for analyses of hematocrit value, erythrocyte and leukocyte counts, and glucose, lactate and cortisol concentrations. Post-mortem measures of meat color and pH were made at 24h and color, shear force and cooking loss on meat from 20 animals at 28days. The AM supplementation resulted in lower hematocrit value, erythrocyte count and glucose level (P<0.05), higher a* (P<0.0001) and b* (P<0.0001) at 24h and lower b* (P<0.05) at 28days. Thus AM treatment improved some stress blood indicators and meat color and therefore merits further investigation.

Synthesis of a phosphinated acetoxybenzoic acid and its application in enhancing Tg and flame retardancy of poly(ethylene terephthalate)

ABSTRACTA new phosphinated acetoxybenzoic acid, 1‐(4‐acetoxyphenyl)‐1‐(4‐carboxylphenyl)‐1‐(6‐oxido‐6H‐dibenz&lt;c,e&gt;&lt;1,2&gt; oxaphosphorin‐6‐yl)ethane (3), was prepared by a three‐step procedure. Phosphinated copolyesters based on the acidolysis and polycondensation of (3) with poly(ethylene terephthalate) (PET) were prepared. The crystallinity of copolyesters decreased gradually with the content of (3), as shown in wide‐angle X‐ray diffractograms and differential scanning calorimetry thermograms. Dynamic mechanical analysis and thermal mechanical analysis show Tg increased with the content of (3). UL‐94 flame retardant test shows that the flame resistance of PET was enhanced with the content of (3), and a copolyester with UL‐94 V‐0 grade can be achieved with a phosphorus content as low as 1.43 wt %. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 424–434

Crystal structures of 4-(oxiran-2-ylmethoxy) benzoic acid and 4-acetoxybenzoic acid

Compounds 4-(oxiran-2-ylmethoxy)benzoic acid (2) and 4-acetoxybenzoic acid (4) are synthesized by a new synthetic route and studied by X-ray crystallography. Compound 2 crystallizes in the monoclinic system, P21/n space group, a = 5.1209(2) A, b = 30.3429(16) A, c = 5.9153(3) A, β = 96.725(3)°, V = 912.81(8) A3, Z = 4. Compound 4 crystallizes in the triclinic system, P-1 space group, a = 7.3400(4) A, b = 8.0819(3) A, c = 15.6548(9) A, α = 85.754(3)°, β = 84.268(2)°, γ = 70.023(3)°, V = 867.63(8) A3, Z = 4. The crystal structure of 2 comprises two crystallographically independent molecules of the compound. In the crystal structures of 2 and 4, pairs of molecules form carboxyl dimers.

Effects of the Heat Treatment on the Mechanical Properties of a Novel Thermotropic Liquid-Crystalline Polymer Fiber

Thermotropic liquid-crystalline polymers (TLCPs) have aroused wide public concern which is attributed to their high strength, stiffness, chemical resistance and perfect dimensional stability as high-performance engineering materials. Vectran heat treated after melt spinning is a representative commercial aromatic copolyester fiber. In this study, a novel TLCP melt-polymerized with 4,4’-diphenyloxide dicarboxylic acid (DODA), 4-acetoxybenzoic acid (ABA), hydroquinone diactate (HQA), 2,6-naphthalene dicarboxylic (NDA) and terephthalic acid (TA) were melt spun into fibers and heat treated to enhance the breaking strength and Young’s modulus. Intermolecular mechanical elements slipped between 120-130 °C and crystallization or the conformational rotations occurred along the extended polymer chain. For this new TLCP fiber, the optimal heat treatment temperature was 260 °C and the suitable heat-treatment time was over 48 hours. The breaking strength, Young’s modulus and breaking elongation of the as-spun fiber were improved from 1.58GPa, 45.21GPa and 1.97% to 3.20GPa, 133.44GPa and 2.42% respectively after heat treatment.

Synthesis and Catalytic Evaluation of Ruthenium–Arene Complexes Bearing Imidazol(in)ium-2-thiocarboxylate Ligands

Five new complexes with the generic formula [RuCl2(p-cymene)(SOC·NHC)] (2–6) were isolated in high yields by reacting the [RuCl2(p-cymene)]2 dimer with a range of imidazol(in)ium-2-thiocarboxylate zwitterions bearing cyclohexyl, 2,4,6-trimethylphenyl (mesityl), or 2,6-diisopropylphenyl groups on their nitrogen atoms in CH2Cl2 at −20 °C. All the products were fully characterized by IR and NMR spectroscopy, and the molecular structures of [RuCl2(p-cymene)(SOC·IMes)] (3) and [RuCl2(p-cymene)(SOC·SIMes)] (5) were determined by X-ray diffraction analysis. Coordination of the NHC·COS ligands took place via the sulfur atom. A remarkable shielding of the methine proton on the p-cymene isopropyl group was observed by 1H NMR spectroscopy for complexes 3–6. It is most likely caused by the aromatic ring current of a neighboring mesityl or 2,6-diisopropylphenyl substituent. The catalytic activity of compounds 2–6 was probed in the ring-opening metathesis polymerization (ROMP) of cyclooctene, in the atom transfer radical polymerization (ATRP) of methyl methacrylate, and in the synthesis of enol esters from 1-hexyne and 4-acetoxybenzoic acid. In all these reactions, the [RuCl2(p-cymene)(SOC·NHC)] complexes displayed performances slightly inferior to those exhibited by [RuCl2(p-cymene)(NHC)] species that result from the reaction of [RuCl2(p-cymene)]2 with NHC·CO2 inner salts. However, they were significantly better catalyst precursors than the much more robust chelates of the [RuCl(p-cymene)(S2C·NHC)]PF6 type obtained by coordination of NHC·CS2 betaines to the ruthenium dimer. These results suggest that the Ru–(SOC·NHC) motif undergoes a dethiocarboxylation under the experimental conditions adopted for the catalytic tests and leads to the same elusive Ru–NHC active species as the preformed [RuCl2(p-cymene)(NHC)] family of complexes.

Properties of Poly(4-hyderoxybenzoate) Oligomer and its Blends with Poly(trimethylene Terephthalate)

The poly(4-hydroxybenzoate) (PHBA) oligomer was synthesized by using the monomer of 4-acetoxybenzoic acid (PABA), and its blends with poly(trimethylene terephthalate) (PTT) are prepared by melt-blending at 250oC in nitrogen. Their chemical structure characterization and crystal morphology were investigated by using the fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (1HNMR), and polarizing optical microscopy, respectively. The results suggest that PHBA oligomer with 3 polymerization degree was synthesized and it is a thermotropic liquid crystal with the nematic characteristics. When the blends crystallize from melt, because the rigid oriented PHBA molecules becomes the nucleating agents for PTT molecules’ crystallization, much transcrystalline layers formed in the blends, although the crystalline PTT/PHBA blends show spherulites morphology character without observing nematic LC phase.

Ruthenium–arene complexes bearing imidazol(in)ium-2-dithiocarboxylate ligands: Evaluation of their catalytic activity in the synthesis of enol esters

The catalytic activity of four ruthenium imidazol(in)ium-2-dithiocarboxylates was evaluated for the synthesis of vinyl esters through addition of 4-acetoxybenzoic acid to 1-hexyne, and compared to those of the parent ruthenium– N-heterocyclic carbene complexes and [RuCl 2( p-cymene)(PPh 3)] (a standard catalyst). It turned out that ruthenium imidazol(in)ium-2-dithiocarboxylates were poorly active and selective. Quantitative yields, indeed, were obtained only after extended reaction times. However, the catalytic activity could be improved significantly under microwave heating or conventional heating in a sealed tube at 160 °C, driving the reaction to completion in less than 4 h of reaction.

The Effect of Solid Sheet Fillers on Poly-p-Oxybenzoate Polymerization, Crystallization and Structure

The effect of added mineral sheet fillers (mica, montmorillonite, talc, graphite and kaolin) on the polymerization of acetoxybenzoic acid was investigated. The fillers exert a weak catalytic effect without affecting the structure and orientation of the polymer, the only exception being mica which can result in an epitaxial orientation.

Solubility of 3,5-Dimethoxybenzoic Acid, 4-Cyanobenzoic Acid, 4-Acetoxybenzoic Acid, 3,5-Diaminobenzoic Acid, and 2,4-Dichlorobenzoic Acid in Ethanol

The solubility of 3,5-dimethoxybenzoic acid, 4-cyanobenzoic acid, 4-acetoxybenzoic acid, 3,5-diaminobenzoic acid, and 2,4-dichlorobenzoic acid in ethanol was measured by both static method and dynamic method over the temperature range from (298.15 to 318.15) K under atmospheric pressure. The experimental data were correlated by the modified Apelblat model. The results show that the solubility of each acid increases with increasing temperature in ethanol, and the data have greater accuracy when using the static method than when using the dynamic method.

Preparation of Poly(4′-oxy-4-biphenylcarbonyl) Needlelike Crystals with the Aid of Copolymerization

Preparation of poly(4′-oxy-4-biphenylcarbonyl) (POBP) needlelike crystals was examined by using reaction-induced crystallization of oligomers during copolymerization of 4-(4-acetoxyphenyl)benzoic acid (APBA) and 4-acetoxybenzoic acid (ABA). Polymerizations were carried out in aromatic solvent at various ABA molar ratios in feed (χf). When the χf was 20−10 mol %, starlike aggregates of needlelike crystals and fibrillated slablike crystals were separately formed, exhibiting similar morphology to poly(4-oxybenzoyl) and POPB crystals. 4-(Oxyphenyl)benzoyl (OPB) homo-oligomers and co-oligomers rich in OPB moiety were more rapidly precipitated due to the lower solubility, and the slablike crystals were formed. Afterward, 4-oxybenzoyl (OB) homo-oligomers and the co-oligomers rich in OB moiety were precipitated to form spindlelike crystals. The OPB homo-oligomers and the co-oligomers rich in OPB moiety were continuously crystallized on both crystals due to the high degree of supersaturation, and the spindlelike crystals grew to the needlelike crystals mainly comprised of POBP. Copolymerization of 4-(4-acetoxybenzoyloxy)benzoic acid and APBA at χf of 10 mol % yielded the needlelike crystals without coexisting fibrillated slablike crystals. This result provides a new methodology for morphology control with the aid of copolymerization.

Polymer whiskers based on p-mercaptobenzoyl and p-oxybenzoyl blocks

Preparation of polymer whisker based on p-mercaptobenzoyl (S) and p-oxybenzoyl (O) blocks was examined by the polymerization of S-acetyl-4-mercaptobenzoic acid (AMBA) and the following addition of 4-acetoxybenzoic acid (ABA). Polymerization of AMBA was carried out in liquid paraffin at 300 °C for 3 h yielding poly( p-mercaptobenzoyl) (PMB) whisker, and then ABA was added stepwise at 3-hour intervals into the solution. Initial polymerization concentration was 1.98%. The length of the whisker increased with the addition and it became 26.7 μm from 20.1 μm after third ABA addition. The width increased very slightly. Both length and width increased with polymer yield but the length increased preferentially rather than the width. The number of whiskers was constant even after the addition of ABA and poly( p-oxybenzoyl) (POB) whisker was not newly formed by the addition. Microscopic FT-IR and selected area electron diffraction measurements revealed that polymer molecules were aligned along the long axis of the whiskers, and the center and tip parts were comprised of PMB crystal and POB crystal, respectively. The polymer whisker based on S and O blocks was successfully prepared as grafting POB crystal on PMB whisker with stepwise addition of ABA. Thermal property of the resulting whiskers was also discussed.

Novel network morphology of poly(p-oxybenzoyl)

Polymerization of 4-acetoxybenzoic acid (ABA) with 3,5-diacetoxybenzoic acid (DABA) was examined to control the morphology of poly(p-oxybenzoyl) (POB). Polymerizations were carried out at a concentration of 1.0% in an aromatic solvent Therm S-1000® (mixture of dibenzyltoluene) at 320 °C. Polymerization of ABA yielded the POB fibrillar crystals, but the polymerization with DABA at a concentration in the feed (χf) of 0.10–0.15 afforded novel network structures comprised of spheres connected by fibrillar crystals. The diameter of the spheres prepared at χf of 0.15, which were 0.7 and 5.0 μm, showed bimodality. The network distance, fibril length, and fibril width were 6.1, 2.6, and 0.1 μm, respectively. They possessed high crystallinity. The network structure was formed as follows. Co-oligomers were first precipitated in the beginning of the polymerization by liquid–liquid phase separation to form the microdroplets. The fibrillar crystals were formed in the coalesced spheres by the crystallization of oligomers induced by the increase of molecular weight. The fibrillar crystals connecting the spheres gradually appeared owing to the shrinkage of the spheres. The fibrillar crystals grew from the surface of the spheres with the crystallization of homo-oligomers of 4-oxybenzoyl units, and finally the network structure was completed. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1624–1634, 2005

Influence of short distance sequence regularity on preparation of poly( p-oxybenzoyl- co- p-mercaptobenzoyl) whisker

Preparation of the poly( p-oxybenzoyl- co- p-mercaptobenzoyl) whiskers was examined by means of the crystallization of oligomers during solution polymerization. Polymerizations were carried out in liquid paraffin at the concentration of 1.0% and 300 °C for 6 h. Copolymerization of 4-acetoxybenzoic acid and S-acetyl-4-mercaptobenzoic acid did not yield the whiskers. This was attributed to tendency that the copolymerization reduced the crystallizability of oligomers and induced the liquid–liquid phase separation of oligomers due to the lower freezing point. In order to induce short distance sequence regularity into oligomers, copolymerizations of two among four monomers were conducted, which were 4-(4-acetoxybenzoyl)oxybenzoic acid, S-(4-acetoxybenzoyl)-4-mercaptobenzoic acid, 4-( S-acetyl-4-mercaptobenzoyl)oxybenzoic acid and S-( S-acetyl-4-mercaptobenzoyl)-4-mercaptobenzoic acid. The copolymerizations of two of these monomers yielded the whiskers but for that of 4-(4-acetoxybenzoyl)oxybenzoic acid and S-( S-acetyl-4-mercaptobenzoyl)-4-mercaptobenzoic acid. The short distance sequence regularity of oligomers brought about the crystallization of oligomers, leading to the formation of whiskers.

Preparation of Poly(p-oxybenzoyl) Microspheres Having Needlelike Crystals on the Surface

Polymerization of 4-acetoxybenzoic acid (ABA) with 3,5-diacetoxybenzoic acid (DABA) was examined to create a novel morphology of poly(p-oxybenzoyl) (POB) by means of the phase separation of oligomers during polymerization. Polymerizations were carried out at a concentration of 1.0% in liquid paraffin at 320 °C. Polymerization of ABA yielded the POB whiskers. On the other hand, the polymerization of ABA with DABA of which the concentration in the feed (χf) was 0.05−0.20 yielded the microspheres having needlelike crystals on the surface. The average diameter of the microspheres was in the range of 3.4−1.6 μm and the average length of the needlelike crystals was 3.2−0.3 μm. The diameter and length decreased with χf. DABA acted as a liquid−liquid phase separation inducer and the liquid−liquid phase separation of co-oligomers comprising 4-oxybenzoyl units and 3,5-dioxybenzoyl units was induced in the beginning of polymerization to form the core microspheres. Then the phase separation mode was changed to the cr...

Kinetics of 4-acetoxybenzoic acid synthesis

High-temperature polymers have found a wide range of uses in recent decades. 4-Acetoxybenzoic acid (PABA) is used as a monomer for the polymerization of one such thermotropic polymer. Information on polycondensation of already prepared PABA is available in the literature. However, information in the literature concerning the kinetics of PABA synthesis by acetylation of 4-hydroxybenzoic acid (PHBA) using acetic anhydride is limited. The reaction between PHBA and acetic anhydride in a carrier solvent, Therminol-66 (T-66), was investigated. Aspects of the global reaction mechanism and the dependence of the reaction rate on acetic anhydride concentration were determined. Nuclear Magnetic Resonance (NMR) spectrometry and gravimetric analysis were used to analyze the samples collected from a 3 l batch reactor. The specific rate constant and the activation energy of the reaction were determined and a rate equation for the reaction suggested.