ChemInform Abstract: pKa and pH Dependence of the Formation of Nitroxide Radicals from Some Drug Substances with an Aliphatic Secondary Amino Group by Oxidation with Hydrogen Peroxide. An ESR Study.

ChemInform ◽  
1988 ◽  
Vol 19 (7) ◽  
Author(s):  
C. LAGERCRANTZ
Keyword(s):  
Hydrogen Peroxide ◽  
Ph Dependence ◽  
Amino Group ◽  
Nitroxide Radicals ◽  
Drug Substances ◽  
Secondary Amino

The reduction of I2 by H2O2 in aqueous solution

2001 ◽  
Vol 79 (3) ◽  
pp. 304-311 ◽  
Author(s):  
J M Ball ◽  
J B Hnatiw
Keyword(s):  
Aqueous Solution ◽  
Hydrogen Peroxide ◽  
Nuclear Reactor ◽  
Ph Dependence ◽  
Radiolysis Product ◽  
Molecular Iodine ◽  
Water Radiolysis ◽  
Reactor Accident ◽  
Rate Law ◽  
Accident Conditions

The reduction of I2 by hydrogen peroxide, a primary water radiolysis product, has been identified as a key reaction that would influence iodine volatility in nuclear reactor accident conditions (1–3). Although there have been a number of studies of the reduction of I2, there exists a great degree of controversy regarding the intermediates involved, the effect of buffers, and the general rate law (1–9). Because the rates and the mechanism of this reaction are important in predicting the pH dependence of iodine behaviour in reactor containment building after a postulated reactor accident, we have undertaken a kinetic study of I2 reduction by H2O2 in aqueous solution over a pH range of 6–9. The experiments were performed using stopped-flow instrumentation and monitoring the decay of I–3 spectrophotometrically. The effects of buffer catalysis have been examined by comparison of kinetic data obtained in sodium barbital (5,5-diethylbarbituric acid), disodium citrate, and disodium hydrogen phosphate buffers. The effect of buffers, combined with the complex acid dependence of the rate law, explains many of the discrepancies reported in earlier literature.Key words: hydrogen peroxide, molecular iodine, kinetics, iodine volatility.

Nitroalkanes as Reductive Substrates for Flavoprotein Oxidases

1972 ◽  
Vol 27 (9) ◽  
pp. 1052-1053 ◽  
Author(s):  
David J. T. Porter ◽  
Judith G. Voet ◽  
Harold J. Bright
Keyword(s):  
Hydrogen Peroxide ◽  
Amino Acid ◽  
Glucose Oxidase ◽  
Ph Dependence ◽  
Kinetic Mechanism ◽  
Acid Oxidase ◽  
Amino Acid Oxidase ◽  
Kinetics Of ◽  
Oxidase Reaction ◽  
Detailed Kinetic Mechanism

Nitroalkanes have been found to be general reductive substrates for D-amino acid oxidase, glucose oxidase and L-amino acid oxidase. These enzymes show different specificities for the structure of the nitroalkane substrate.The stoichiometry of the D-amino acid oxidase reaction is straightforward, consisting of the production of one mole each of aldehyde, nitrite and hydrogen peroxide for each mole of nitroalkane and oxygen consumed. The stoichiometry of the glucose oxidase reaction is more complex in that less than one mole of hydrogen peroxide and nitrite is produced and nitrate and traces of 1-dinitroalkane are formed.The kinetics of nitroalkane oxidation show that the nitroalkane anion is much more reactive in reducing the flavin than is the neutral substrate. The pH dependence of flavin reduction strongly suggests that proton abstraction is a necessary event in catalysis. A detailed kinetic mechanism is presented for the oxidation of nitroethane by glucose.It has been possible to trap a form of modified flavin in the reaction of D-amino acid oxidase with nitromethane from which oxidized FAD can be regenerated in aqueous solution in the presence of oxygen.

Amino Acid Salt Catalyzed Asymmetric Addition Reaction of Acetylacetone to Maleimides and 2-(2-Oxoindolin-3-ylidene)malononitriles

Synlett ◽  
2019 ◽  
Vol 30 (10) ◽  
pp. 1241-1245 ◽  
Author(s):  
Haiyan Wu ◽  
Hongxin Liu ◽  
Juan Li ◽  
Xinhua Li ◽  
Hong-Ping Xiao ◽  
...  
Keyword(s):  
Amino Acid ◽  
Addition Reaction ◽  
Optical Purity ◽  
Activation Mechanism ◽  
Amino Group ◽  
Acid Salt ◽  
Natural Amino Acid ◽  
Catalytic Potential ◽  
Amino Acid Salt ◽  
Secondary Amino

The exploration of catalytic potential of natural amino acid salt in activation of 1,3-dicarbonyls was carried out, in which maleimides and 2-(2-oxoindolin-3-ylidene)malononitriles were found to be good electrophiles and afforded the desired products with excellent yield and moderate optical purity. Control experiments showed that the secondary amino group of barium (S)-prolinate is critical to the catalytic activity as well as enantiocontrol, thus revealed an enamine activation mechanism is possible in the present methodology.

Photochemical redox reactions at the zinc oxide-water interface in additive-free systems

1971 ◽  
Vol 24 (6) ◽  
pp. 1193 ◽  
Author(s):  
DR Dixon ◽  
TW Healy
Keyword(s):  
Hydrogen Peroxide ◽  
Redox Reactions ◽  
Heterogeneous Reaction ◽  
Ph Dependence ◽  
H2o2 Production ◽  
Water Interface ◽  
General Reaction ◽  
Interstitial Zinc ◽  
Different Gases ◽  
Hydrolysis Of

When aqueous ZnO suspensions, saturated with oxygen, are irradiated with u.v. light, hydrogen peroxide is formed and a decrease in pH is observed. The effects of different gases (O2, N2, and N2O) on the course of this heterogeneous reaction and also the pH dependence of the reaction have been examined. On the basis of the results obtained, the mechanism which had been previously suggested was modified to allow for the hydrolysis of the zinc(II) ions removed from the crystal lattice during irradiation. A general reaction mechanism proposed to account for H2O2 production in systems with various additives present is extended to additive-free systems where interstitial zinc (Zn1+) is the effective reductant.

pKa-Werte von Ethidiumbromid und 7-Amino-9-phenyl-10- äthyl-phenanthridinium-bromid / pKa-Values of Ethidiumbromide and 7-Amino-9-phenyl-10-ethyl-phenanthridinium- bromide

1976 ◽  
Vol 31 (11-12) ◽  
pp. 656-660 ◽  
Author(s):  
Ingfried Zimmermann ◽  
Herbert Zimmermann
Keyword(s):  
Electronic Spectra ◽  
Water Solution ◽  
Ph Dependence ◽  
Quantum Mechanical ◽  
Amino Group ◽  
Quantum Mechanical Calculations ◽  
Acidic Water ◽  
Amino Groups ◽  
Electronic Density ◽  
Decreasing Ph

Abstract Ethidiumbromide (1) has two amino groups in 2-and 7-position which are protonated in acidic water solution. Both pKa-values of 1 are determined at 20 °C by means of the pH-dependence of the electronic spectra using a iterative calculating procedure, pKa1 = 0.713, pKa2 = 2.43. Acetylation of 1 and quantum mechanical calculations lead to the conclusion that the electronic density at the 7-amino group is greater than in 2-position. Therefore with decreasing pH preferably the 7-amino group is protonated (pKa2). followed by the protonation of the 2-amino group (pKa1). The pKa of 7-amino-9-phenyl-10-ethyl-phenanthridinium-bromide in water solution at 20 °C is determined to pKa= 1 .2 5 .

pH Dependence and Structural Interpretation of the Reactions ofCoprinus cinereusPeroxidase with Hydrogen Peroxide, Ferulic Acid, and 2,2‘-Azinobis(3-ethylbenzthiazoline-6-sulfonic acid)†

Biochemistry ◽  
1997 ◽  
Vol 36 (31) ◽  
pp. 9453-9463 ◽  
Author(s):  
A. Katrine Abelskov ◽  
Andrew T. Smith ◽  
Christine Bruun Rasmussen ◽  
H. Brian Dunford ◽  
Karen G. Welinder
Keyword(s):  
Hydrogen Peroxide ◽  
Ferulic Acid ◽  
Sulfonic Acid ◽  
Ph Dependence ◽  
Structural Interpretation

Cu(I)-Catalyzed Intramolecular Hydroamination of Unactivated Alkenes Bearing a Primary or Secondary Amino Group in Alcoholic Solvents

2009 ◽  
Vol 11 (10) ◽  
pp. 2145-2147 ◽  
Author(s):  
Hirohisa Ohmiya ◽  
Toshimitsu Moriya ◽  
Masaya Sawamura
Keyword(s):  
Amino Group ◽  
Secondary Amino

The reaction of 2,4,6-trinitrobenzene sulfonic acid with pancreatic elastase

1970 ◽  
Vol 48 (11) ◽  
pp. 1249-1259 ◽  
Author(s):  
Leticia Rao ◽  
T. Hofmann
Keyword(s):  
Rate Constant ◽  
Sulfonic Acid ◽  
Ph Dependence ◽  
Order Rate Constant ◽  
Trinitrobenzene Sulfonic Acid ◽  
Amino Group ◽  
Tyrosine Residues ◽  
Inactivation Rate Constant ◽  
Lysine Residues ◽  
Ph Range

The reaction of elastase with trinitrobenzene sulfonic acid was investigated in the pH range 9–12. Elastase was found to be inactivated by 2,4,6-trinitrobenzene sulfonic acid. The pH dependence of the pseudo first-order inactivation rate constant showed a pK of 10.3 and gave a Hill plot coefficient of 1.15. Trinitrophenol did not inactivate the enzyme. These results indicate that the inactivation is due to the covalent reaction of trinitrobenzene sulfonic acid with a single group in the enzyme. This group is not the N-terminal since the loss of N-terminal valine was considerably slower than the loss of activity at pH 10.5. The inactivation of elastase with 2,4-dinitrofluorobenzene also showed no correlation with the loss of the N-terminal. When the enzyme was exhaustively treated and fully inactivated with trinitrobenzene sulfonic acid at pH 10.5, the N-terminal valine and two out of three lysine residues were trinitrophenylated. No evidence for the loss of histidine was found. One of the tyrosine residues may be trinitrophenylated as judged from the molar extinction of the trinitrophenylated protein, but it has not been possible to isolate a trinitrophenylated tyrosine-containing peptide. The results can be interpreted in one of two ways: (a) trinitrophenylation of a group with a pK of 10.3, not involved in the activity, inactivates because the introduction of the trinitrophenyl residue causes a denaturation of the enzyme; or (b) a group with a pK of 10.3 controls the active conformation of the enzyme. The results do not exclude the possibility that the N-terminal plays an important role in the activity of the enzyme. Below pH 10.5 the reactivity of the N-terminal is low, indicating that it is buried.At pH 9.0 only the ε-amino group of lysine in position 224 reacted with trinitrobenzene sulfonic acid and full activity was retained. The second-order rate constant for the trinitrophenylation of this group was 25 times higher than that of the ε-amino group of the α-N-benzoyllysine.

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