Unusual Inverse Temperature Dependence on Reaction Rate in the Asymmetric Autocatalytic Alkylation of Pyrimidyl Aldehydes

2010 ◽  
Vol 132 (43) ◽  
pp. 15104-15107 ◽  
Author(s):  
Michela Quaranta ◽  
Timo Gehring ◽  
Barbara Odell ◽  
John M. Brown ◽  
Donna G. Blackmond
Keyword(s):  
Temperature Dependence ◽  
Reaction Rate ◽  
Inverse Temperature

Kinetik der Reaktion von 2.4-Dinitrofluorbenzol mit Imidazol-, SH- und Imidazol-SH-Verbindungen / Kinetics of the Reaction of 2,4-dinitro-1-fluorobenzene with Imidazole-, SH- and Imidazole-SH-compounds

1971 ◽  
Vol 26 (10) ◽  
pp. 1010-1016 ◽  
Author(s):  
Renate Voigt ◽  
Helmut Wenck ◽  
Friedhelm Schneider
Keyword(s):  
Temperature Dependence ◽  
Rate Constants ◽  
Reaction Rate ◽  
Ph Dependence ◽  
First Order ◽  
Molecular Transfer ◽  
Thiolate Anion ◽  
Nucleophilic Reactivity ◽  
Kinetics Of ◽  
Lindley Equation

First order rate constants of the reaction of a series of SH-, imidazole- and imidazole/SH-compounds with FDNB as well as their pH- and temperature dependence were determined. Some of the tested imidazole/SH-compounds exhibit a higher nucleophilic reactivity as is expected on the basis of their pKSH-values. This enhanced reactivity is caused by an activation of the SH-groups by a neighbouring imidazole residue. The pH-independent rate constants were calculated using the Lindley equation.The kinetics of DNP-transfer from DNP-imidazole to SH-compounds were investigated. The pH-dependence of the reaction displays a maximum curve. Donor in this reaction is the DNP-imidazolecation and acceptor the thiolate anion.The reaction rate of FDNB with imidazole derivatives is two to three orders of magnitude slower than with SH-compounds.No inter- or intra-molecular transfer of the DNP-residue from sulfure to imidazole takes place.

scholarly journals PERIODATE OXIDATION OF PEG–600, AN ESSENTIAL PHARMACEUTICAL POLYMER

2019 ◽  
pp. 251-256
Author(s):  
K. V. S. KOTESWARA RAO ◽  
R. VENKATA NADH ◽  
K. VENKATA RATNAM
Keyword(s):  
Polyethylene Glycol ◽  
Oxygen Atom ◽  
Temperature Dependence ◽  
Reaction Rate ◽  
Periodate Oxidation ◽  
Alkali Concentration ◽  
Rate Of Reaction ◽  
Atom Loss ◽  
Kinetics Of ◽  
Peg 600

Objective: To study the kinetics of periodate oxidation of polyethylene glycol-600 (PEG-600), a familiar non-toxic polymer used in pharmaceutical and other fields of industry. Methods: Reactions were carried out in alkaline medium and measured the kinetics by iodometry. One oxygen atom loss or two electrons transfer was observed per each molecule of periodate i.e., the rate of reaction was measured periodate converts to iodate because the formed iodate species is unable to oxidize the substrate molecules. Results: Based on log (a-x) versus t plots, order w. r. t. oxidant (periodate) is unity. Reactions were found to be independent of substrate (PEG-600) concentration. A decrease in rate with an increase in alkali concentration [OH–] was found and order was inverse fractional. Temperature dependence of reaction rate was studied and then calculated the corresponding Arrhenius parameters. Conclusion: An appropriate rate law was proposed by considering the above experimental results.

Crossover from Normal to Inverse Temperature Dependence in the Adsorption of Nonionic Surfactants at Hydrophilic Surfaces and Pore Walls†

2007 ◽  
Vol 111 (43) ◽  
pp. 16045-16054 ◽  
Author(s):  
Oliver Dietsch ◽  
Anton Eltekov ◽  
Henry Bock ◽  
Keith E. Gubbins ◽  
Gerhard H. Findenegg
Keyword(s):  
Temperature Dependence ◽  
Nonionic Surfactants ◽  
Inverse Temperature ◽  
Hydrophilic Surfaces

Radiolysis of Supercritical Water at 400°C: A Sensitivity Study of the Density Dependence of the Yield of Hydrated Electrons on the (eaq−+eaq−) Reaction Rate Constant

2016 ◽  
Vol 2 (2) ◽  
Author(s):  
Sunuchakan Sanguanmith ◽  
Jintana Meesungnoen ◽  
David A. Guzonas ◽  
Craig R. Stuart ◽  
Jean-Paul Jay-Gerin
Keyword(s):  
Temperature Dependence ◽  
Density Dependence ◽  
Rate Constant ◽  
Supercritical Water ◽  
Reaction Rate ◽  
Reaction Rate Constant ◽  
Sudden Drop ◽  
Alkaline Water ◽  
Hydrated Electrons ◽  
Neutral Water

The temperature dependence of the rate constant (k) of the bimolecular reaction of two hydrated electrons (eaq−) measured in alkaline water exhibits an abrupt drop between 150°C and 200°C; above 250°C, it is too small to be measured reliably. Although this result is well established, the applicability of this sudden drop in k(eaq−+eaq−)) above ∼150°C to neutral or slightly acidic solution, as recommended by some authors, still remains uncertain. In fact, the recent work suggested that in near-neutral water the abrupt change in k above ∼150°C does not occur and that k should increase, rather than decrease, at temperatures greater than 150°C with roughly the same Arrhenius dependence of the data below 150°C. In view of this uncertainty of k, Monte Carlo simulations were used in this study to examine the sensitivity of the density dependence of the yield of eaq− in the low–linear energy transfer (LET) radiolysis of supercritical water (H2O) at 400°C on variations in the temperature dependence of k. Two different values of the eaq− self-reaction rate constant at 400°C were used: one was based on the temperature dependence of k above 150°C as measured in alkaline water (4.2×108  M−1 s−1), and the other was based on an Arrhenius extrapolation of the values below 150°C (2.5×1011  M−1 s−1). In both cases, the density dependences of our calculated eaq− yields at ∼60  ps and 1 ns were found to compare fairly well with the available picosecond pulse radiolysis experimental data (for D2O) for the entire water density range studied (∼0.15–0.6  g/cm3). Only a small effect of k on the variation of G(eaq−)) as a function of density at 60 ps and 1 ns could be observed. In conclusion, our present calculations did not allow us to unambiguously confirm (or deny) the applicability of the predicted sudden drop of k(eaq−+eaq−) at ∼150°C in near-neutral water.

Kinetics and Inverse Temperature Dependence of a Tsuji–Trost Reaction in Aqueous Buffer

ACS Catalysis ◽  
2019 ◽  
Vol 9 (12) ◽  
pp. 11720-11733 ◽  
Author(s):  
Ivanna Pohorilets ◽  
Matthew P. Tracey ◽  
Michael J. LeClaire ◽  
Emily M. Moore ◽  
Gang Lu ◽  
...  
Keyword(s):  
Temperature Dependence ◽  
Inverse Temperature ◽  
Aqueous Buffer
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