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Hydrolysis Mechanism (hydrolysis + mechanism)
Selected AbstractsUse of real-time FT-IR monitoring of a pharmaceutical compound under stress atmospheric conditions to characterize its solid-state degradation kineticsINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 1 2010Peter J. Skrdla The use of online FT-IR is described for investigating the degradation kinetics of the solid amorphous pharmaceutical compound, fosaprepitant dimeglumine (FD), under stress storage conditions (i.e., high temperature, T, and humidity, % RH). It is found that under conditions of elevated T and % RH, the kinetics are denucleation rate limited for the deliquescence of the amorphous FD solid, based on the high quality fits obtained to the authors' dispersive kinetic model for that mechanism. At elevated T and low % RH, it is found that a classical, first-order hydrolysis mechanism for the degradation of FD (which forms crystalline aprepitant, AP) significantly contributes to the overall conversion rate. That mechanism is similar to the one observed previously for the solution-phase hydrolysis of FD. Appropriate kinetic models are proposed for the FD-to-AP conversion under all of the experimental conditions investigated in this work. © 2009 Wiley Periodicals, Inc. Int J Chem Kinet 42: 25,36, 2010 [source] A DFT study on the hydrolysis mechanism of NH-tautomeric antitumors of [HL][trans -RuCl4L(dmso- S)]INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 6 2010Jin Can Chen Abstract The hydrolysis process of Ru (III) complex [Htrz][trans -RuCl4(1- H -1,2,4-triazole)(dmso- S)] 1, a potential antitumor complex similar to the well-known anticancer agent [ImH][trans -RuCl4(Im)(dmso- S)] (NAMI-A), has been investigated by using density functional theory (DFT) method, and the solvent effect was also considered and calculated by conductor-like polarizable calculation model (CPCM). Meanwhile, the hydrolysis process of the NH-tautomeric isomer, [Htrz][trans -RuCl4(4- H -1,2,4-triazole)(dmso- S)] 2, was also modeled and predicted by the same methods. The structural characteristics and the detailed energy profiles for the hydrolysis processes of two isomers have been obtained. The analysis of thermodynamic and kinetic characteristics of hydrolysis reaction suggests the following: for the first hydrolysis step, the Complex 1 has lower hydrolysis rate than the reported anticancer drug NAMI-A, and the result is in accordance with experimental one. However, Complex 1 has obviously higher hydrolysis rate than its isomer Complex 2, and the result was reasonably explained in theory. For the second hydrolysis step, the formation of cis -diaqua species is thermodynamic preferred to that of trans isomers. In addition, the trend in nucleophilic attack abilities (A) of hydrolysis products by pertinent biomolecules was revealed and predicted. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010 [source] Electrodeposition of Titania Thin Films on Metallic Surface for High- k Dielectric ApplicationsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 3 2010Biplab K. Roy Current microelectronics devices based on flexible as well as rigid substrates demand high dielectric constant (k) films to be grown on conductive substrate from a low-cost, low-temperature deposition technique. In this study, we produced high- k titania (TiO2) films through an affordable electrodeposition protocol from the electrochemical bath maintained at about 0°C. The deposition occurs through a rapid hydrolysis mechanism of titanium containing ions in the precursor solution aided by electrochemically generated hydroxyl ions formed near the cathode surface (copper (Cu) substrate). Upon attaining a sufficient supersaturation level, such hydrolyzed species precipitate to form a titania thin film on the cathode surface. While depositing from a highly acidic precursor solution, Cu substrate was protected by a cathodic potential (,3 to ,5 V against the counter electrode). The resultant titania films show nanoparticulate structures evolved from nucleation and growth events of the in situ precipitated particles. Much higher deposition rate (about 1 ,m/min) was observed compared with that of typical chemical bath deposition. The resultant films with a thickness of 1500 nm grown on Cu exhibit very high dielectric properties (e.g., k,30, capacitance density >110 nF/in.2 at 100 kHz) and moderate breakdown voltage (VB) (,17.5 V). These properties indicate the potential of electrodeposited titania films to be used as a small-area thin-film capacitor for miniaturized electronic devices. [source] Impact of improved phosphite hydrolytic stability on the processing stabilization of polypropyleneJOURNAL OF VINYL & ADDITIVE TECHNOLOGY, Issue 4 2005Brian Johnson It is well known that some high-performance phosphite antioxidants are particularly sensitive to hydrolysis. This process has two principal consequences: 1) the creation of potential handling issues, as the product can become sticky, and 2) a possible loss in the performance of this type of antioxidant. In this article both of these are addressed. First, changes in the hydrolytic stability of a high-performance phosphite are examined by formulating with co-additives of different chemical natures. Second, changes in the hydrolytic stability of the phosphite when using different additive physical forms are investigated. Third, the influence of hydrolysis on the processing stabilization performance of the high-performance phosphite is evaluated. It is seen that the rate of hydrolysis of the high-performance phosphite is drastically reduced both by altering the physical form of the additive package and by the correct selection of the co-additive package. This selection not only extends the storage life of the high-performance phosphite but also minimizes the risk of any handling issues. Furthermore, it is concluded that hydrolysis does not necessarily mean a loss in performance but, contrary to general perception, can actually lead to an enhancement of the processing stability. The final conclusion of this study is that the hydrolysis mechanism of the phosphite is strongly influenced by the physical form of the additive package and by the chemical nature of the co-additives. This difference in mechanism is responsible for a different level of processing performance but is not discussed in detail in this publication. J. VINYL. ADDIT. TECHNOL. 11:136,142, 2005. © 2005 Society of Plastics Engineers. [source] 17O NMR investigation of phosphite hydrolysis mechanismsMAGNETIC RESONANCE IN CHEMISTRY, Issue 12 2007Sarah K. McIntyre Abstract The use of solution 17O NMR spectroscopy in verifying the mechanism of trialkyl phosphite hydrolysis is presented. Trimethyl phosphite was reacted with 17O-labeled H2O at different temperatures and two reactant concentrations, with the reaction being monitored by 17O NMR. Kinetic details elucidated from the NMR spectra are also discussed. Copyright © 2007 John Wiley & Sons, Ltd. [source] | |||||||||||||