Enolization of the benzocyclohexadienone formed during the bromination of 1-naphthol in aqueous solution

1987 ◽  
Vol 65 (8) ◽  
pp. 1714-1718 ◽  
Author(s):  
Oswald S. Tee ◽  
N. Rani Iyengar
Keyword(s):  
Aqueous Solution ◽  
Carboxylic Acid ◽  
Hydroxide Ion ◽  
A Value ◽  
Ph Range ◽  
Effective Molarity ◽  
Kinetics Of

Benzo-4-bromo-2,5-cyclohexadienone (5) has been observed in the aqueous bromination of 1-naphthol and the kinetics of its enolization to 4-bromo-1-naphthol have been studied in the pH range 0–7. This process is catalyzed by the proton, hydroxide ion, water, buffer acids, and by buffer bases. For catalysis by general bases the Brønsted β = 0.59 whereas catalysis by general acids has a value of α ~ 0. These findings are very similar to those obtained previously for the 4-bromo-2,5-cyclohexadienone 2b, formed during the aqueous bromination of 2,6-dimethylphenol. The mechanistic implications of the results are discussed. The enolization of the related dienone 8, formed from bromine and 1-naphthol-2-carboxylic acid, was also studied. At acidic pHs the dienone 8 is much more reactive than 5, with the 2-COOH behaving as an internal catalyst having an "effective molarity" of about 110 M. The enolization of 8 is also catalyzed by buffer bases.

Stability of the Nerve Gas Antidote BIS (4-Hydroxyiminomethyl-1-Pyridinomethyl) Ether Dichloride (Toxogonin®)

1968 ◽  
Vol 2 (9) ◽  
pp. 234-243 ◽  
Author(s):  
Inga Christenson
Keyword(s):  
Aqueous Solution ◽  
Hydrochloric Acid ◽  
Sodium Hydroxide ◽  
Rate Constants ◽  
Kinetics Of Hydrolysis ◽  
Dilute Aqueous Solution ◽  
Nerve Gas ◽  
Ph Range ◽  
Kinetics Of ◽  
Hydrolysis Of

The products and kinetics of hydrolysis of the nerve gas antidote bis(4-hydroxyiminomethyl - 1 - pyridinemethyl) ether dichloride (Toxogonin ®) have been investigated. A survey of these studies is given: The hydrolytic reactions were studied in the pH range 1 M hydrochloric acid to 1 M sodium hydroxide at 25, 45, 75 and 85° C. Rate constants were determined in dilute aqueous solution, generally with an initial Toxogonin concentration of 0.01 mg per ml. In addition, a report is given concerning two-year storage of 25 percent (w/v) Toxogonin solutions at pH 2.5, 3.0 and 3.5. The solutions were stored in glass or polypropylene ampuls at 5, 15, 25 and 45°C. At 5 and 15C° decomposition was negligible, at 25 and 45 °C average decomposition was 1.5 percent and 3.3 percent, respectively.

Host-Guest Complexation of Aromatic Carboxylic Acids and their Conjugate Bases by β-Cyclodextrins Monosubstituted at C 6 by Linear and Cyclic Alkyl Triamines in Aqueous Solution

1999 ◽  
Vol 52 (12) ◽  
pp. 1157 ◽  
Author(s):  
Suzanna D. Kean ◽  
Bruce L. May ◽  
Philip Clements ◽  
Christopher J. Easton ◽  
Stephen F. Lincoln
Keyword(s):  
Aqueous Solution ◽  
Carboxylic Acid ◽  
Complex Stability ◽  
Guest Complex ◽  
Acid Complex ◽  
K Value ◽  
Host Guest Complex ◽  
Ph Range ◽  
Conjugate Bases ◽  
Significant Factors

A pH titrimetric study of the complexation of the guests benzoic acid, 4-methylbenzoic acid and (R)- and (S)-2-phenylpropanoic acids and their conjugate bases by the host 6A-[2-(2-aminoethylamino)ethylamino]-, 6A-[3-(3-aminopropylamino)propylamino]-, 6A-(1,4,7-triazacyclononan-1-yl)-, and 6A-(1,5,9-triazacyclododecan-1-yl)-6A-deoxy-β-cyclodextrins (βCDdien, βCDdipn, βCDtacn and βCDtacdo, respectively) is reported. Over the pH range 3.0–11.0, 49 host–guest complexes were detected. Their stability constants (K) range from 220±50 dm3 mol–1 for the βCDdienH22+ ·benzoate– complex to 48000±11000 dm3 mol–1 for the βCDdipnH22+·(S)-2-phenylpropanoic acid complex at 298.2 K and I = 0.10 mol dm–3 (NaClO4). The latter K value is among the highest reported for a complex of a simple carboxylic acid with a substituted β-cyclodextrin. The charge, hydrophobicity and stereochemistry of both host and guest appear to be significant factors in the variation of host–guest complex stability. 1H ROESY n.m.r. studies of some of the complexes formed are also reported.

scholarly journals The kinetics of mutarotation in solution

1940 ◽  
Vol 176 (966) ◽  
pp. 352-367 ◽  
Keyword(s):  
Aqueous Solution ◽  
Room Temperature ◽  
Reducing Sugars ◽  
Arrhenius Equation ◽  
Energy Of Activation ◽  
A Value ◽  
Temperature Ranges ◽  
Velocity Coefficient ◽  
Kinetics Of ◽  
True Energy

The kinetics of the mutarotation of representative reducing sugars from the pentose, hexose and disaccharide series have been investigated polarimetrically over wide temperature ranges in aqueous solution. The dependence of the velocity coefficient, k , upon temperature is fairly well reproduced by an equation of the form ln k = C + ( J/R ) ln T - E/RT . The true energy of activation, E , is found to be some 6000 calories greater than the apparent value afforded by the Arrhenius equation at room temperature. J/R has a value of — 10, which is identified as the number of oscillators contributing to the activation. The constants C, J and E of this equation are discussed, with reference to many reactions, in terms of a theory of unimolecular reactions in solution.

Ruthenium and iron complexes of dipicolinic acid: Synthesis, solution properties and kinetics of electron transfer reactions with ascorbate ions

1983 ◽  
Vol 36 (12) ◽  
pp. 2377 ◽  
Author(s):  
NH Williams ◽  
JK Yandell
Keyword(s):  
Redox Potential ◽  
Rate Constant ◽  
Dipicolinic Acid ◽  
Acid Synthesis ◽  
Equilibrium Mixture ◽  
A Value ◽  
Inert Electrode ◽  
Ph Range ◽  
Kinetics Of ◽  
Kinetics Of Reduction

Standard potentials of the redox couples [bis(pyridine-2,6-dicarboxylate)MIII]-/2- ([M(dipic)2]-/2-, where M = Fe, Ru, Co) have been determined at 25�C, and ionic strength 0.1M (NaClO4 or KNO3). Kinetics of reduction of the oxidized complexes by ascorbate have also been examined under the same conditions. The [Fe(dipic)2]-/2- potential was found to be 355 � 5 mV. Reduction of [Fe(Fe(dipic)2]- in the pH range 4-6 was shown to occur by reaction with ascorbate monoanion (HA-) with a rate constant of (2.2 � 0.2) × 103 1. mol-1 s-1, and ascorbate dianion(A2-) with a rate constant of (7 � 1) × 108 1. mol-1 s-1. K [Ru(dipic)2] has been synthesized. Spectroscopic and analytical evidence suggest that it is a simple six-coordinate species in the solid and in non-aqueous solvents, but that in water it exists as an equilibrium mixture of at least two species. The redox potential for this mixture was found to be 270 � 10 mV. The major component of this mixture is reduced by A2- with a rate constant of (4.7 � 0.1) × 1081.mol-1 s-1. A value of 747 � 5 mV was measured for the redox potential of the cobalt couple, although equilibration of this system with the inert electrode could be achieved only by using [Fe(bpy)2(CN)2] as a mediator. Kinetics of reduction of [Co(dipic)2]- by ascorbate were complex and not reproducible.

scholarly journals Kinetics and Mechanism of the Decarboxylation of Pyrrole-2-carboxylic Acid in Aqueous Solution

1971 ◽  
Vol 49 (7) ◽  
pp. 1032-1035 ◽  
Author(s):  
G. E. Dunn ◽  
Gordon K. J . Lee
Keyword(s):  
Aqueous Solution ◽  
Ionic Strength ◽  
Carboxylic Acid ◽  
Isotope Effect ◽  
Anthranilic Acid ◽  
Kinetic Isotope Effect ◽  
Pyrrole Ring ◽  
First Order ◽  
Kinetic Isotope ◽  
Ph Range

The decarboxylation of pyrrole-2-carboxylic acid in aqueous buffers at 50° and ionic strength 1.0 has been found to be first order with respect to substrate at a fixed pH. As the pH is decreased, the rate constant increases slightly in the pH range 3–1, then rises rapidly from pH 1 to 10 M HCl. The 13C-carboxyl kinetic isotope effect is 2.8% in 4 M HClO4 and negligible at pH ~ 3. These observations can be accounted for by a mechanism, previously proposed for the decarboxylation of anthranilic acid, in which the species undergoing decarboxylation is the carboxylate ion protonated at the 2-position of the pyrrole ring. This intermediate can be formed both by ring-protonation of the carboxylate anion and by ionization of the ring-protonated acid. At low acidities ring-protonation is rate determining, but at higher acidities the rate of protonation exceeds that of decarboxylation.

scholarly journals Temperature and pH effects on the kinetics of 2-aminophenol auto-oxidation in aqueous solution

2003 ◽  
Vol 1 (3) ◽  
pp. 233-241 ◽  
Author(s):  
Dumitru Oancea ◽  
Mihaela Puiu
Keyword(s):  
Experimental Data ◽  
Activation Energy ◽  
Aqueous Solution ◽  
Ph Effects ◽  
Influence Of Temperature ◽  
First Order ◽  
Incremental Methods ◽  
First Order Kinetics ◽  
Ph Range ◽  
Kinetics Of

AbstractThe kinetics of the auto-oxidation of 2-aminophenol (OAP) to 2-amino-phenoxazin-3-one (APX) was followed in air-saturated aqueous solutions and the influence of temperature and pH on the auto-oxidation rate was studied. The kinetic analysis was based on a spectrophotometric method following the increase of the absorbance of APX. The process follows first order kinetics according to the rate law—d[OAP]/dt=k′[OAP]. The experimental data, within the pH range 4–9.85, were analyzed using both differential and incremental methods. The temperature variation of the overall rate constant was studied at pH=9.85 within the range 25–50°C and the corresponding activation energy was evaluated.

THE CHEMISTRY OF ETHYLENE OXIDE: II. THE KINETICS OF THE REACTION OF ETHYLENE OXIDE WITH AMINES IN AQUEOUS SOLUTION

1951 ◽  
Vol 29 (7) ◽  
pp. 575-584 ◽  
Author(s):  
A. M. Eastham ◽  
B. deB. Darwent ◽  
P. E. Beaubien
Keyword(s):  
Aqueous Solution ◽  
Ethylene Oxide ◽  
Order Equation ◽  
Basic Catalysis ◽  
Ion Concentrations ◽  
Hydroxyl Ion ◽  
Wide Range ◽  
Dilute Aqueous Solution ◽  
Ph Range ◽  
Kinetics Of

The kinetics of the reaction of ethylene oxide in dilute aqueous solution at 25°C. with di- and tri-ethylamines, aniline, and pyridine have been investigated over a wide range of hydrogen and hydroxyl ion concentrations. The rates for all four amines were found to be very similar and were accurately expressed by the simple second order equation −d oxide/dl = k(oxide)(amine). The results indicate that basic catalysis does not occur and that catalysis by hydrogen or ammonium-type ions, if it occurs at all, is of no significance in the pH range 4–14.

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