Effect of ultrasound on ester hydrolysis in aqueous ethanol

Tuulmets, Ants; Salmar, Siim

doi:10.1016/s1350-4177(01)00078-5

Cited by 26 publications

(37 citation statements)

References 47 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…For the acid-catalyzed hydrolysis of ethyl acetate we observed a similar dependence of the sonication effect on solvent composition. [19,20] These results initially led us to think that sonication effects were merely related to a perturbation of the solvent system. However, on replacing ethyl acetate with more hydrophobic esters, we observed a dramatic change in the dependence of the sonication effect on solvent composition, which obliged us to revise our early point of view.…”

Section: Resultsmentioning

confidence: 99%

“…This enabled us to work with a very low ester concentration (10 À5 M) and to avoid resorting to the internal standard used in the GLC method (cf. References [19,20] ).…”

Section: Resultsmentioning

confidence: 99%

“…Our contribution to HI studies consists in applying power ultrasound to kinetic investigation of polar (ionic) homogeneous reactions in solutions, mainly in ethanol-water binary mixtures. [19][20][21][22][23] Ultrasonic acceleration effects on chemical processes are widely exploited both in the laboratory and industrial practice. [24][25][26] Sonication mostly affects reaction rates, yields, and in some cases the ratios of reaction products.…”

Section: Introductionmentioning

confidence: 99%

“…Sonication studies of solvolysis/hydrolysis reactions in aqueousorganic binary solvents have brought to light specific solutesolvent interactions and hydrophobic effects that are not manifested in conventional kinetic investigations. [19][20][21][22][23][27][28][29] It was concluded that in these cases the sonochemical effects may be related to the perturbation of the molecular structure of the solvent and, more critically, to the destruction of hydrophobic solute-solvent interactions.…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Ultrasonic detection of hydrophobic interactions: a quantitative approach

Tuulmets

Järv

Salmar

et al. 2008

J of Physical Organic Chem

View full text Add to dashboard Cite

Kinetic effects of sonication on ester hydrolysis and tert-butyl chloride solvolysis, studied in ethanol-water binary solvent, are discussed in terms of quantitative relationships between their magnitude and the hydrophobicity of reagents. A number of conclusions were drawn from the observed linear free-energy (LFE) relationships. Independent of reaction mechanism, the decrease in reaction rates with increasing ethanol content in the solvent is mainly due to hydrophobic stabilization of the ground state. While hydrophobic species can be hidden in the ethanol clusters present in the region X EtOH > 0.15, at lower ethanol contents hydrophobic reagents are weakly solvated and the hydrophobic stabilization can be easily overcome by sonication.

show abstract

Section: Resultsmentioning

confidence: 99%

“…This enabled us to work with a very low ester concentration (10 À5 M) and to avoid resorting to the internal standard used in the GLC method (cf. References [19,20] ).…”

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Ultrasonic detection of hydrophobic interactions: a quantitative approach

Tuulmets

Järv

Salmar

et al. 2008

J of Physical Organic Chem

View full text Add to dashboard Cite

show abstract

“…The influence of ultrasound on the kinetic parameters of electrochemical redox reactions was investigated by Jung et al [9]. The kinetics of the acidcatalyzed hydrolysis of ethyl acetate in ethanol-water binary solutions was investigated by Tuulmets and Salmar [10].…”

Section: Introductionmentioning

confidence: 99%

Effect of Ultrasound on the Production Reaction Kinetics of Sodium Thiosulfate

Ingec¹,

Tekin

2004

Chem Eng & Technol

View full text Add to dashboard Cite

It is known that the production reaction of sodium thiosulfate which consists of the reaction of Na 2 SO 3 with sulfur is considerably slow. Ultrasound energy was used to increase the conversion fraction of sulfur and to accelerate the production reaction of Na 2 S 2 O 3 , and the effect of ultrasonic energy on the reaction kinetics was investigated. The particle size, reaction temperature, concentration of Na 2 SO 3 solution and amplitude of ultrasound power were chosen as parameters. The experiments were performed in the absence and presence of ultrasound. Considering the results the reaction is chemically controlled first order and the activation energy is equal to 42 kJ/mol in both cases. The results indicated that the ultrasound energy increased the reaction speed but it did not vary the activation energy. The effect of ultrasound is on the pre-exponential factor A. Finally, an empirical relation is given which relates the rate constant to ultrasound power.

show abstract

Degradation and stabilization of cosmetic polyetherurethane in alcoholic solution

Kim

Park

Bae

2003

J of Applied Polymer Sci

View full text Add to dashboard Cite

A polyetherurethane (PEU) was synthesized for potential cosmetic applications by coupling poly(tetramethylene oxide) (PTMO, M n ϭ 2000 g mol Ϫ1 ) and poly-(ethylene oxide) (PEO, M n ϭ 2000 g mol Ϫ1 ) with 4,4'-diphenylmethane diisocyanate (MDI), without using a chain extender. The PEU polymer, synthesized with PEO and PTMO in the ratio of 1:3 by weight, was soluble in ethanol-water mixed solvents. The solution formed a thin film in situ on the skin by coating, which was flexible and elastomeric with appropriate skin adhesiveness. However, PEU was susceptible to degradation when it was exposed to an ethanolwater (80/20 v/v %) mixed solvent and stored in an airfilled and sealed bottle at 60°C for 4 weeks. These conditions resulted in deterioration of PEU molecular weight (M n ), viscosity, and mechanical properties. Peak analysis of the Fourier transform infrared spectrum of the aged PEU revealed that Ͼ97% of the urethane carbonyl bonds remained, whereas ether bonds were significantly reduced (ϳ82% of initial value). The degraded PEU contained ester bonds, which were confirmed by proton and carbon-13 nuclear magnetic resonance spectroscopy. This observation suggests that oxidative chain cleavage rather than hydrolysis was the dominant reaction in the degradation process. Two approaches were adopted to minimize oxidative degradation of PEU dissolved in an ethanol-water (80/20 v/v %) mixed solvent; they were, applying a nitrogen environment and adding an antioxidant (1.8 wt % dry PEU). The results indicate that reduction of oxidative degradation produced a synergistic effect. Vitamin E was a more effective antioxidant than butylated hydroxytoluene (BHT), which is a typical antioxidant for commercial polyurethanes.

show abstract

Effect of ultrasound on ester hydrolysis in aqueous ethanol

Cited by 26 publications

References 47 publications

Ultrasonic detection of hydrophobic interactions: a quantitative approach

Ultrasonic detection of hydrophobic interactions: a quantitative approach

Effect of Ultrasound on the Production Reaction Kinetics of Sodium Thiosulfate

Degradation and stabilization of cosmetic polyetherurethane in alcoholic solution

Contact Info

Product

Resources

About