Ester Hydrolysis Rate Constant Prediction from Quantum Topological Molecular Similarity Descriptors

2003 ◽  
Vol 107 (22) ◽  
pp. 4578-4582 ◽  
Author(s):  
U. A. Chaudry ◽  
P. L. A. Popelier
Keyword(s):  
Rate Constant ◽  
Molecular Similarity ◽  
Ester Hydrolysis ◽  
Hydrolysis Rate ◽  
Hydrolysis Rate Constant

Effect of ultrasonic treatment on swine wastewater solubilization

2009 ◽  
Vol 59 (3) ◽  
pp. 603-608 ◽  
Author(s):  
Y. H. Lee ◽  
S.-M. Kim ◽  
S. Na ◽  
K.-H. So ◽  
J.-J. Nam
Keyword(s):  
Rate Constant ◽  
Ultrasonic Treatment ◽  
Operating Temperature ◽  
Operation Time ◽  
Order Rate Constant ◽  
Swine Wastewater ◽  
Energy Conditions ◽  
Hydrolysis Rate ◽  
Operational Conditions ◽  
Hydrolysis Rate Constant

In order to accelerate hydrolysis known to be the rate-limiting step of the overall digestion process for swine wastewater, an ultrasonic treatment process was tested for the solubilization of the swine wastewater. The effectiveness of ultrasonic solubilization of the swine wastewater under various operational conditions was compared by means of an increment of soluble organics in the treated swine wastewater and the hydrolysis rate constant. Ultrasonic treatment resulted in the high degree of solubilization of particulate organics in the swine wastewater and the degree of solubilization increased with increasing supplied energy. The highest extent of an increment of SCOD concentration and SCOD/TCOD ratio at the end of the operation time of 60 min was 109.7 and 117.5%, respectively, under 120 W power output and 20oC operating temperature conditions. The observed highest hydrolysis rate constant described by pseudo-first order rate constant was 2.94 h−1 under the same conditions. Based on the estimated activation energy from modeling using the Arrhenius equation, ultrasonic solubilization of the swine wastewater under higher supplied energy conditions was more dependent on the operating temperature, which was consistent with the experimentally obtained results. Based on the investigation into the effect of gas type and gas delivery methods for ultrasonic solubilization of the swine wastewater, oxygen gas bubbling through the liquid showed the highest degree of an increment of soluble organics possibly attributed to the influent of oxygen in an increase of radicals during the sonolysis.

A new in-situ method to determine the hydrolysis rate constant of adenosine triphosphate (ATP) by application of Raman spectroscopy in a hydrothermal diamond anvil cell

2021 ◽  
Author(s):  
Christoph Moeller ◽  
Christian Schmidt ◽  
Francois Guyot ◽  
Max Wilke
Keyword(s):  
Adenosine Triphosphate ◽  
Rate Constant ◽  
Rate Constants ◽  
Diamond Anvil Cell ◽  
Elevated Temperatures ◽  
Hydrolysis Rate ◽  
Extreme Conditions ◽  
Hydrolysis Rate Constant ◽  
Diamond Anvil

<p>In recent decades increasing evidence was found for life under extreme conditions, e.g., near black smokers on the ocean floor. The synthesis and stability of vital molecules like adenosine triphosphate (ATP) and adenosine diphosphate (ADP) are essential to maintain the metabolism of all known organisms. The lifetime of these molecules in water is limited by the non-enzymatic hydrolysis reaction that becomes dominant at elevated temperatures. A better understanding of this mechanism will provide us insights of life at extreme conditions.</p><p>Previous studies determined the hydrolysis rate constants of ATP for several compositions, temperatures and pressures using quench experiments and subsequent analysis. So far, it was not tested whether quench artefacts might have affected those results. Therefore, the current study was performed to develop a method to follow the reaction in-situ with a high sampling rate at elevated temperatures. A confocal micro-Raman spectrometer and a hydrothermal diamond anvil cell were used to perform experiments at elevated temperatures and vapour pressure. Spectra were obtained in the range of 660 cm<sup>-1</sup> to 1157 cm<sup>-1</sup> as a function of time. Different solutions of ATP and ADP were measured at 353 K, 373 K, and 393 K, at starting pH values of 3 and 7. First findings are consistent with previous studies and show that with decreasing pH value the hydrolysis rate increases. The data indicate hydrolysis rate constants in the magnitude of 10<sup>-3</sup> s<sup>-1</sup> by 393 K, 10<sup>-4</sup> s<sup>-1</sup> by 373 K and 10<sup>-5</sup> s<sup>-1</sup> by 353 K. These initial observations show that this technique produces reliable kinetic data on this reaction. It also provides much better sampling statistics than quench experiments. </p><p>The high reaction rates suggest that a mechanism exists to regulate this reaction at higher temperatures, which is necessary to allow metabolism under extreme conditions. Moreover, it is commonly known that ATP interacts with various metal ions with different effects on the reaction rate. An application of this method would be the quantification of the hydrolysis rate constant in chemically more complex systems.</p>

Solvolysis kinetics of ethyl 3-ethoxy-3-iminopropanoate

1986 ◽  
Vol 51 (3) ◽  
pp. 677-683 ◽  
Author(s):  
Jaromír Kaválek ◽  
Josef Panchartek ◽  
Tomáš Potěšil ◽  
Vojeslav Štěrba
Keyword(s):  
Water Molecule ◽  
Rate Constant ◽  
Hydrolysis Rate ◽  
Nucleophilic Attack ◽  
Tetrahedral Intermediate ◽  
Hydrolysis Rate Constant ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Rate Limiting ◽  
Kinetics Of

Kinetics have been studied of hydrolysis and methanolysis of ethyl 3-ethoxy-3-iminopropanoate. The methanolysis rate constant is lower than the hydrolysis rate constant by about 3 orders of magnitude. The rate-limiting step of the hydrolysis consists in the nucleophilic attack of the protonated substrate by a water molecule, whereas that of the methanolysis consists in the decomposition of tetrahedral intermediate which is several orders of magnitude slower than the decomposition of the intermediate formed in the hydrolysis.

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