Rates Of Alkaline Hydrolysis Research Articles

TRANSMISSION OF POLAR SUBSTITUENT EFFECTS IN 4`-SUBSTITUTED DIPHENYLACETYLENE-4-CARBOXYLIC ACIDS

A series of 4'-substituteddiphenylacetylene-4-carboxylic acids' alkaline hydrolysis rate coefficients were measured in 70%(v/v) dimethyl sulfoxide- water at 30.0 C. Using a solution of 80% (w/w) 2-methoxyethanol - water at 25.0 C, the pKa values of 4'- substituted diphenylacetylene-4-carboxylic acids have been determined. Esterification rate constants of corresponding acids with diazodiphenylmethane have been measured at 300C. For the transmission of dipolar ireversible dipolar substituent effects were seen for 4' - substituted diphenylacetylene-4-carboxylic acids. it was normal substituent effects are observed from 4`-substituted diphenylacetylene-4-carboxylic acids .Therefor it is conceivable to explain clearly the polar of substituent effect of the transmission via path of direct field of electrostatic in this system according to the results shown in tables 8,10 and 12

A multiple linear regression approach to the estimation of carboxylic acid ester and lactone alkaline hydrolysis rate constants

ABSTRACT Pesticides, pharmaceuticals, and other organic contaminants often undergo hydrolysis when released into the environment; therefore, measured or estimated hydrolysis rates are needed to assess their environmental persistence. An intuitive multiple linear regression (MLR) approach was used to develop robust QSARs for predicting base-catalyzed rate constants of carboxylic acid esters (CAEs) and lactones. We explored various combinations of independent descriptors, resulting in four primary models (two for lactones and two for CAEs), with a total of 15 and 11 parameters included in the CAE and lactone QSAR models, respectively. The most significant descriptors include pK a, electronegativity, charge density, and steric parameters. Model performance is assessed using Drug Theoretics and Cheminformatics Laboratory’s DTC-QSAR tool, demonstrating high accuracy for both internal validation (r 2 = 0.93 and RMSE = 0.41–0.43 for CAEs; r 2 = 0.90–0.93 and RMSE = 0.38–0.46 for lactones) and external validation (r 2 = 0.93 and RMSE = 0.43–0.45 for CAEs; r 2 = 0.94–0.98 and RMSE = 0.33–0.41 for lactones). The developed models require only low-cost computational resources and have substantially improved performance compared to existing hydrolysis rate prediction models (HYDROWIN and SPARC).

Transmission of dipolar substituent effects: ionization of a series 3-(7-substituted-1-naphthyl) propynoic acid (E)-3-(7-substituted-1-naphthyl) propenoic acids and their Esterification with Diazodiphenylmethane

Alkaline hydrolysis rates coefficients for the series of methyl 3-(7-substituted-1-naphthyl) propynoate was calculated in 70%v/v dimethylsulphoxide-water at various temperatures (25,30,40, and 50̊ C). The pKa values of 3-(7-substituted-1-naphthyl) propynoic acid and (E)- 3-(7-substituted-1-naphthyl) propenoic acid calculated in 80%w/w 2-methoxyethanol-water at room temperature (25.0̊ C). logk2 of esterification rate coefficients for 3-(7-substituted-1-naphthyl) propynioc acid and (E)-3(7-substituted-1-naphthyl) propenioc acid with DDM have been measured at 30.0̊ C. Reversed substituent dipolar effects were found in the ionization reaction. In the esterification reaction with DDM the result show similar but reduced substituted effects. Rate retardations was found in the alkaline hydrolysis. It could be result from steric effect or reversal of substituent dipolar effect with a combination of steric effect.

Shrinking Particle Reaction Model for a Waste Double‐Base Propellant During Alkaline Hydrolysis

AbstractDouble‐base propellants are widely used in missiles and rocket engines. Waste double‐base propellants must be safely disposed of because their safety and reliability greatly deteriorate during storage and use. Alkaline hydrolysis is a promising alternative to the open burning and open detonation disposal methods of waste propellants. To promote the industrialization of the alkaline hydrolysis treatment of waste double‐base propellants, a reaction model of the alkaline hydrolysis of SC double‐base propellants was studied. First, the relationship between the concentration of nitrite‐nitrogen and nitrate‐nitrogen in the alkaline hydrolysate was studied. The results revealed that a good linear relationship between the concentration of nitrite‐nitrogen and nitrate‐nitrogen (slope is 1.771, R2 is 0.9925). The waste SC granules produce fewer nitrite ions than fresh nitrocellulose and nitroglycerin. Secondly, based on the analysis results of scanning electron microscopy, energy‐dispersive X‐ray spectroscopy, and the thickness of SC granules before and after alkaline hydrolysis, it was assumed that the reaction model was a shrinking particle reaction model, and the limiting step was the alkaline hydrolysis rate on the surface of granules. Then, the relationship between the alkaline hydrolysis degree xSC of SC granules and reaction time t was xSC=((α+2)/(2te))t‐(α/(2te2))t2 by theoretical reaction model derivation. Additionally, the reaction model and limiting step were experimentally validated. Thus, this study provides theoretical and technical support for the safe industrial deposal and resource utilization of waste SC and other double‐base propellants with nitrocellulose and nitroglycerin as basic energetic components, as well as a basis for its fundamental research.

Inhibitive Effect on the Rate of Hydrolysis of Tetracaine by the Surfactant-Coated Magnetic Nanoparticles (Fe3O4)

The influence of the magnetic nanoparticles Fe3O4 and surfactant coated nanoparticles on the rate of alkaline hydrolysis of tetracaine were investigated spectrophotometrically. The Fe3O4 nanoparticles were synthesized by co-precipitation method. These synthesized nanoparticles were characterized by physical techniques. The XRD patterns showed the crystalline nature and the presence of two bands at 635 cm -1 and 585 cm -1 were assigned to the Fe-O bond vibrations in Fe3O4. The SEM and TEM studies confirmed the spherical structure of nanoparticles. The VSM studies show the magnetic nature. The reaction rate increased linearly with increase in [NaOH]. The rate constant values decreased with the increase in the SDS coated Fe3O4 nanoparticles from 4.0 × 10 -4 s -1 to 1.1 × 10 -4 s -1 in the presence of PEG 1500. Similarly, the increase in the amount of CTABr coated Fe3O4 nanoparticles decreased the rate constant values from 4.0 × 10 -4 s -1 to 1.02 × 10 -4 s -1 in the presence of PEG 1500. The binding constant and rate constant were found to be lower in SDS coated nanoparticles than the CTABr coated particles. The observed results for - [surfactant] in the presence of magnetic nanoparticles and surfactant coated nanoparticles were treated using the pseudophase kinetic model.

Unexpected Z/E isomerism of N-methyl-O-phosphothioyl benzohydroxamic acids, their oxyphilic reactivity and inertness to amines

Thiophosphinoylation of N-methyl p-substituted benzohydroxamic acids using disulfanes (method A) or diphenylphosphinothioyl chloride (method B) provides only one conformer of the respective O-phosphothioyl derivative (X-ray and NMR analysis). Undergoing the P-transamidoxylation reaction is an evidence of the reversibility of thiophosphinoylation. Only those products containing strong EWG substituents in the aroyl residue or bulky substituents at the phosphorus atom possess E conformation. DFT calculations confirmed the energetic domination of each isomer. The Z-isomers are distorted amides having both high degree of nitrogen pyramidalization (38–55°) and amide twist (12–30°). In solution they exist in a defined conformation that is evidenced by the presence of a sharp signal of N-methyl protons at low temperature. They do not isomerize in solutions. Some of them slowly undergo the N-O bond scission above 100 °C. Both isomers are not as sensitive to neutral hydrolysis as twisted amides can be and are inert toward amines. The rate of alkaline hydrolysis can be correlated with pKa of hydroxamic acid. Because of their outstanding oxyphilicity, these compounds can be defined as nerve agent surrogates and safer alternatives of phosphorus fluorides for serine-active enzyme inhibition studies.

Influence of PVP-PEG mixed aggregates and electrolytes on the rate of alkaline hydrolysis of benzocaine in aqueous and surfactant medium

The present work describes the effects of the interactions between the two water-soluble polymers poly(vinyl pyrrolidone) (PVP) and poly(ethylene glycol) (PEG) on the rate of the alkaline hydrolysis of benzocaine. The roles of the surfactants cetyltrimethylammonium bromide (CTABr) and sodium dodecyl sulfate (SDS) in the binding of benzocaine with PVP-PEG mixed systems has also been explored through changes in the reaction rate. Our results revealed that the reaction rate decreases with the increasing [PVP] when [PEG] is fixed. Similarly, the rate of hydrolysis also decreases on increasing [PEG] while [PVP] is fixed. The combined rate constant values for the hydrolysis of benzocaine in the aqueous and mixed PVP-PEG system (kΨ) increases with increasing [CTABr] in the lower concentration range, then decreases with further increase in [CTABr], giving a peaked profile for kΨ vs. [CTABr]. The increase in [SDS] in the mixed PVP-PEG system decreases the rate of hydrolysis. Accordingly, the observed results show that the binding constant values (i.e., the degree of association) of benzocaine with PVP-PEG in the presence of CTABr and SDS are lower. Furthermore, increasing the molecular weight of PEG in the surfactant-PVP-PEG complex decreases the binding constant values of the benzocaine-polymer complex due to the formation of less compact aggregates. The effects of electrolytes (CH3COONa, NaCl, Na2SO4, and NaNO3) were also investigated, and they were found to decrease reaction rate.

Influence of the hydration and dynamics behaviour of polyvinylpyrrolidone on the rate of alkaline hydrolysis of benzocaine

The aggregation and hydrodynamic behaviour of polyvinylpyrrolidone (PVP) in aqueous medium have been studied through the kinetics involving the alkaline hydrolysis of benzocaine. The absorbance values recorded for benzocaine at different [PVP] demonstrate that the absorbance intensities change with the increase in [PVP]. The kinetics studies on the hydrolysis of benzocaine at different [PVP] and [PVP-surfactant] have also been undertaken to further elaborate the morphological changes in PVP in the absence and presence of surfactants. The values of rate constant decrease with the increase in [PVP] in the lower PVP concentrations range. In the middle concentration range, the rate constant values do not change with change in [PVP]. At higher [PVP], i.e. in the polymer chain entanglement region of [PVP], the values of rate constant decreased again. The obtained results for the absorbance and the rate constant values are the consequences of different morphological arrangement of PVP and the hydration ratio around PVP chains. The values of rate constant gave peak behaviour with [CTABr] in the presence of PVP. The plot obtained for kΨ-[SDS] contains two crests with the increase in [SDS] due to different conformational arrangements formed between the PVP chain and SDS molecules. The resulting trends in the values of rate constant versus [surfactant] are the result of partitioning of the reacting species (OH– and Bz) into different pseudophases due to divergent organisation between PVP and surfactant molecules. Viscosity measurements and TEM images at different [PVP] support the structural changes occurring in the PVP chains in aqueous medium.

Influence of surfactants and surfactant-coated IONs on the rate of alkaline hydrolysis of procaine in the presence of PEG

The influence of surfactant coated iron oxide nanocomposites (Surf-IONs) and surfactants on the rate of alkaline hydrolysis of procaine hydrochloride (2-diethylaminoethyl-4-aminobenzoic acid) in the presence of poly(ethylene glycol) (PEG) have been investigated under the varying reaction conditions. The nanoparticles were synthesised using the co-precipitation method and were characterised using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Vibrating sample magnetometer (VSM) and Thermogravimetric analysis (TGA). The concentration of NaOH was taken in overabundance over [procaine] for maintaining the reactions under pseudo-first-order conditions. The kinetic effect of poly(ethylene glycol); PEG of molecular weights 1500, 4000, 6000, and 8000 with the cetyltrimethylammonium bromide; CTABr and sodium dodecyl sulphate; SDS (either free or coated on iron oxide nanoparticles) were studied. A fall in the values of the rate constant on increasing the [surfactant] or [Surf-IONs] at fixed [PEG] was observed. The kψ-[PEG-surfactant] profile was treated using the pseudophase model, and pseudophase ion exchange model and the kinetic parameters were determined. The binding constant of procaine with PEG-surfactant aggregates was found to be lower than the respective micelles in the absence of PEG. The increase in the molecular weights of PEG decreased the values of binding constants and equilibrium constants.

Influence of polyethylene glycol and surfactant mixed system on the rate of alkaline hydrolysis of benzocaine

The rate of alkaline hydrolysis of benzocaine has been studied spectrophotometrically in the presence of polyethylene glycols (PEGs), surfactants (cetyltrimethylammonium bromide; CTABr and sodium dodecyl sulphate; SDS) and in the mixed media of surfactants-polysurfactants (PEGs-CTABr and PEGs-SDS). The observed values of rate constant increased linearly with the increase in [NaOH] at fixed [benzocaine] obeying the equation: kobs = k2[NaOH]. The rate constant – [CTABr] plot showed peaked behaviour whereas in case of SDS, the rate constant decreased with increase in [SDS]. The increase in the molecular weight of PEGs increased the binding tendency of PEG-CTABr system for benzocaine, in turn, an increase in inhibitory effect on the rate of hydrolysis was observed. The obtained values of the binding constant decreased with the increase in the molecular weight of PEGs in PEG-SDS mixed system. The binding constant and the values of rate constant in the surfactant, PEG-surfactant media were determined by using Pseudophase Ion Exchange (PIE) and pseudophase models.

Reaction yield model of nitrocellulose alkaline hydrolysis.

Military nitrocellulose waste is flammable and explosive, and thus requires safe disposal and resource utilization. The alkaline hydrolysis process is a potential treatment method for nitrocellulose waste. In this study, a reaction yield model of nitrocellulose alkaline hydrolysis reaction was studied. For this purpose, a theoretical reaction yield model of nitrocellulose alkaline hydrolysis was developed based on Fick's law and scanning electron microscopy analysis. Additionally, the reaction yield model was experimentally validated. The results revealed a linear relationship between the nitrocellulose alkaline hydrolysis rate of xNC and the reaction time of t, which is given by t/tf = xNC. The limiting step of the alkaline hydrolysis of nitrocellulose is the rate of diffusion of OH- through the large pore channels. Accordingly, the reaction rate of the nitrocellulose alkaline hydrolysis can be increased by increasing the KOH concentration, reaction temperature, and reducing the size of the nitrocellulose granules. Thus, this model provides theoretical and technical support for the safe disposal and resource utilization of nitrocellulose waste.

Synergistic influence of inhibition of PEG-surfactant on the rate of alkaline hydrolysis of procaine

The effect of surfactants (sodium dodecyl sulphate; SDS, cetyltrimethyl ammonium bromide; CTABr, and Triton X-100; TX100) and polymeric surfactants (viz. polyethylene glycol; PEG) mixture on the rate of base catalyzed hydrolysis of procaine hydrochloride (2-diethylaminoethyl-4-aminobenzoic acid) has been studied under the pseudo-first-order conditions ([OH¯]≫[Procaine]). The rate of hydrolysis of procaine was found to be linearly dependent upon the [NaOH] in the range from 2.0×10−2moldm−3 to 8.0×10−1moldm−3 at fixed [procaine] (=5.0×10−5moldm−3) at 37°C. The values of rate constant were found to be independent on [procaine] in the concentration range from 1.0×10−5moldm−3 to 1.0×10−4moldm−3 at a fixed concentration of NaOH at 5.0×10−2moldm−3. The values of rate constant decreased with the increase in the concentrations of surfactants (SDS, CTABr and TX100). The rate of hydrolysis further decreased with the addition of PEGs of different molecular weights (1500, 4000, 6000 and 8000) in the reaction media containing surfactant. The increase in the concentration of PEGs from 1% to 5% decreased the rate of hydrolysis, thereby, increasing its stability. The increase in molecular weight of PEG also decreased the rate of hydrolysis. The kinetic parameters and binding constants (e.g. km, Kp for the different reaction media) were calculated for the reactions occurring in the aqueous and surfactant-PEG pseudophases by applying pseudophase ion exchange model. Maximum inhibition in the rate of hydrolysis was observed for PEG-TX100 aggregates.

Modifying the surface of poly(ethylene terephthalate) nanofibrous materials by alkaline treatment and TiO2 nanoparticles

The mutual effects of nano-TiO2 and alkaline hydrolysis on the morphology, chemical structure, water absorption, and the dyeing behavior of poly(ethylene terephthalate) nanofibers were investigated via employing scanning electron microscope, Fourier Transform Infra Red Spectroscopy (FTIR) and X-ray diffraction, and measuring water contact angle, 3M repellency, and dye absorption. A direct relation between the alkaline hydrolysis rate and nanofibers hydrophilicity was observed, while the addition of the nano-TiO2 led to more hydrophobicity. However, the alkaline hydrolysis had the prominent effect. FTIR spectra illustrated no chemical interaction between the nanoparticles and nanofibers. It was also shown that the dye absorption at dyeing equilibrium and the rate of dyeing were increased by the presence of the nano-TiO2 and these effects were intensified by the alkaline hydrolysis. These observations were related to the reduction in the nanofibers diameter and the increase in the surface roughness, as evidenced in the scanning electron microscope, and the increase in the amorphous regions of the nanofibers, as shown by the X-ray diffraction diffractograms.

Ultrasound-Assisted Alkaline Hydrolysis of Waste Poly(Ethylene Terephthalate) in Aqueous and Non-aqueous Media at Low Temperature

This work demonstrates an attempt to depolymerize the waste poly(ethylene terephthalate) (PET) at low temperature using 20 kHz frequency ultrasound. Alkaline hydrolysis of PET was carried out in an aqueous as well as in methanolic medium. Ultrasound has shown a significant enhancement in the rate of alkaline hydrolysis of PET in methanol compared to an aqueous medium. The rate of alkaline hydrolysis of PET increases with an increase in the temperature and alkali concentration. PET conversion of 69% and 46% was observed with and without ultrasound, respectively, using 10% (w/w) sodium hydroxide (NaOH)-methanol solution at 50°C temperature in 60 min. Pure terephthalic acid was recovered from the PET and characterized using Fourier-transform infrared spectroscopy and acid number. The shrinking core model was proposed for the reaction mechanism with surface reaction as the rate of the controlling step. Kinetic analysis indicates almost equal activation energy and yet shows a significant difference in the frequency factor with and without ultrasound-assisted alkaline hydrolysis. Thus, ultrasound does not alter the intrinsic mechanism of PET hydrolysis. The reason for enhancement in the rate of reaction may be the ultrasound-induced micro-mixing and thereby the frequency of interaction between PET and NaOH molecules.

Solvent Effect on the Enthalpy and Entropy of Activation for the Hydrolysis of Ethyl Cinnamate in Mixed Solvent System

The rate of alkaline hydrolysis of ethyl cinnamate was measured over the temperature range of 20°C to 40°C in water-acetone mixture at different composition 30 to 70% (v/v). The influence of solvent variation on reaction rate was examined in term of changes in the Activation parameter. Depletion of ?H* and ?S* value with simultaneous increase in ?G* of the reaction in reaction media, reveals that the reaction is Enthalpy domination and Entropy controlled. The Iso- dielectric activation energy (ED) of reaction was found to decrease from 52.43 to 47.28. The Values of Iso-kinetic Temperature which is less than 300, clearly indicates that there is no appreciable interaction between solvent and solute present in the reaction media, i.e., reaction is not ion-dipole but ion-molecule type.

Solubility and hydrolytic stability of indomethacin in aqueous micellar solutions

The solubility of the indomethacin drug in aqueous micellar solutions of a series of dicationic surfactants was characterized by spectrophotometry. The use of these surfactants can significantly increase the indomethacin content in aqueous solutions without destruction of the drug. The increase in the solubility can be explained by the multifactorial mechanism of the influence of micelles involving the solubilization of the drug and its binding with surfactants due to electrostatic and specific interactions. The use of dicationic surfactants in alkaline solutions was shown to markedly accelerate the hydrolytic cleavage of indomethacin. The highest catalytic effect is observed for N,N´-(hexane-1,6-diyl)bis(2-hydroxyethyl)(methyl)(cetyl)ammonium dibromide: a 1200-fold increase in the reaction rate of alkaline hydrolysis of the drug.

Kinetic investigation on alkaline hydrolysis of tris-(2,2ʹ-bipyridine)iron(II) in CTAB reverse micellar media

The alkaline hydrolysis of tris-(2,2ʹ-bipyridyl)iron(II) complex has been studied in the CTAB/1-butanol/n-heptane reverse micellar media. The reaction obeys second-order kinetics: first order with respect to each of complex and alkali. Observed pseudo-first order rate constant (kobs) has been determined at different values of W and Z. Rate initially increases and then decreases with increase in W, showing a maximum at W=7.41. Concentration of CTAB, at constant values of W and Z, has no effect on reaction rate; indicates that the reaction occurs inside the reverse micellar cavity of water pool. Below W=7.41, both the rate of dissociation and alkaline hydrolysis proceed parallel with a moderate speed. With the increase in Z, concentration of butanol in the water pool increases; decreases the micro-polarity of the water pool and hence increases the rate. The kinetic results are interpreted using the pseudo-phase model.

Micellar effects upon the rate of alkaline hydrolysis of triflusal

The rate of hydrolysis for triflusal was measured at varying concentrations of NaOH at four different temperatures (i.e. 25, 35, 45 and 55°C). The micelles of cetyltrimethylammonium bromide (CTABr), cetyltrimethylammonium chloride (CTACl), cetyltrimethylammonium hydroxide (CTAOH) and dodecyltrimethyl-ammonium bromide (DTABr) had catalytic effect on the rate of hydrolysis. CTABr, CTACl and DTABr gave maxima like curve for the rate–[surfactant] plot while CTAOH gave plateau like curve. The anionic sodium dodecyl sulfate (SDS) did not influence the rate of alkaline hydrolysis of triflusal. The non-ionic Brij-35 inhibited the rate of the hydrolytic reaction. The catalytic effect by cationic micelles was treated by applying the pseudophase ion exchange model while the inhibitive effect by non-ionic micelles has been described by using the Poisson–Boltzmann pseudophase model. The variation in kψ with the change in [surfactant] was used to determined various kinetic parameters e.g., binding constant (Ks), and micellar rate constant (km). The addition of electrolytes decreased the reaction rate in CTABr and CTAOH micelles.

Micellar Effects upon the Alkaline Hydrolysis of Acetaminophen Prodrugs: Carboxylic and Carbonic Acid Esters

The rates of alkaline hydrolysis for four carboxylate esters (4-acetaminophenyl acetate, 4-acetaminophenyl butyrate, 4-acetaminophenyl heptanoate and 4-acetaminophenyl benzoate) and three carbonate ester (4-acetaminophenyl methylcarbonate, 4-acetaminophenyl ethylcarbonates and 4-acetaminophenyl propylcarbonates) prodrugs of acetaminophen derivatives were determined in aqueous and micellar media. The cationic micelles of cetyltrimethylammonium bromide (CTABr) and cetyltrimethylammonium sulfate [(CTA)2SO4] catalyzed the rate of the reaction. The anionic sodium dodecyl sulphate (SDS) and non-ionic Brij-35 surfactants inhibited the rate of the reaction. Added salt did not influence the rate of the reaction in the aqueous medium but decreased the values of observed rate constant in the micellar media. The rate enhancement in cationic micelles was treated by applying the pseudophase ion exchange model while the inhibition effect on the rate of hydrolysis was described using the Poisson–Boltzman pseudophase model. The binding constant (K s ) for the acetaminophen derivatives increased with increasing hydrocarbon chain length while the values of micellar rate constant (k m ) decreased with the increase in chain length. The increase in values of K s and decrease in k m are ascribed to the hydrophobic interaction between the acetaminophen derivative and surfactant molecule and molecular orientation of the substrate in the micelles.

Effect of cosolvents in the presence of sodium dodecyl sulfate micelles on the rate of alkaline hydrolysis of tris(2,2′-bipyridine)iron(II) complex

The kinetics of alkaline hydrolysis of tris(2,2′-bipyridine)iron(II) complex have been studied in the presence of various alcohols of different chain lengths and number of OH groups in aqueous and SDS micellar medium. In aqueous medium, rate increases at all percentages of 1-alkanols in the following order: PrOH>EtOH>MeOH>H2O, whereas the effectiveness of glycols as inhibitors is in the following order: Gly>EG>PG>H2O. Hence PrOH has the most pronounced effect as accelerator and Gly as inhibitor on rate. In the presence of SDS micelles, rate has been inhibited because of binding of SDS with substrate, but the presence of alcohols reduces this inhibitory effect of SDS. All these results have been explained in terms of the CMC, micellar size and properties of SDS in these cosolvents, H-bonding capacity of solvents, dielectric constants of the media, etc.