scholarly journals Vinyl ether hydrolysis. XIV. 2-Methoxy-2,3-dihydropyran: concurrent reaction of vinyl ether and acetal functional groups

1980 ◽  
Vol 58 (21) ◽  
pp. 2199-2202 ◽  
Author(s):  
R. A. Burt ◽  
Y. Chiang ◽  
A. J. Kresge
Keyword(s):  
Vinyl Ether ◽  
Isotope Effect ◽  
Reaction Rate ◽  
Functional Group ◽  
Minor Amount ◽  
Cyanoacetic Acid ◽  
Buffer Solutions ◽  
Hydrogen Isotope Effect ◽  
A Minor ◽  
Hydrolysis Of

The hydrolysis of 2-methoxy-2,3-dihydropyran shows a normal isotope effect (kH/kD > 1) under catalysis by the hydrogen ion and gives an accurately linear dependence of reaction rate upon undissociated acid concentration in cyanoacetic acid and formic acid buffer solutions. This substrate, therefore, unlike its higher homolog, 9-methoxyoxacyclonon-2-ene, provides no evidence in support of an anything but a normal mechanism for vinyl ether hydrolysis. Analysis of the hydrogen isotope effect suggests that a minor amount (8%) of this hydrolysis occurs via reaction of the acetal functional group.

scholarly journals Isothermal and non-isothermal kinetics of hydrolysis of 1-[2-(2- pentyloxyphenylcarbamoyloxy)-(2-methoxymethyl)-ethyl]- perhydroazepinium chloride (BK 129)

2013 ◽  
Vol 60 (2) ◽  
pp. 43-48
Author(s):  
Stankovičová M. ◽  
Bezáková Ž. ◽  
Beňo P. ◽  
Húšťavová P.
Keyword(s):  
Biological Activity ◽  
Alkaline Hydrolysis ◽  
Functional Group ◽  
Isothermal Kinetics ◽  
Basic Part ◽  
Buffer Solutions ◽  
Kinetics Of Hydrolysis ◽  
Short Time ◽  
Kinetics Of ◽  
Hydrolysis Of

Abstract The substance BK 129 - 1-[2-(2-pentyloxyphenylcarbamoyloxy)-(2-methoxymethyl)-ethyl]-perhydroazepinium chloride was prepared in terms of influence of the connecting chain between the carbamate functional group and the basic part of molecule on biological activity. Such a structural feature is important with regard to its stability. In this work we determined the rate constants of alkaline hydrolysis of this compound at increased temperature under isothermal and non-isothermal conditions. The hydrolysis was also performed in buffer solutions with the purpose of evaluating its stability. Non-isothermal tests of stability enable to reduce the number of analyses. The necessary data for stability of compound are in this way achieved in a short time.

Vinyl ether hydrolysis. XIII. The failure of I-strain to produce a change in rate-determining step

1980 ◽  
Vol 58 (2) ◽  
pp. 124-129 ◽  
Author(s):  
Y. Chiang ◽  
W. K. Chwang ◽  
A. J. Kresge ◽  
S. Szilagyi
Keyword(s):  
Vinyl Ether ◽  
Acid Catalysis ◽  
Isotope Effects ◽  
Kinetic Isotope Effects ◽  
Mineral Acid ◽  
Buffer Solutions ◽  
Rate Determining Step ◽  
Kinetic Isotope ◽  
Acetic Acid Buffer ◽  
Hydrolysis Of

Rates of hydrolysis of 1-ethoxy-3,3,5,5-tetramethylcyclopentene and 1-methoxy-2,3,3,5,5-pentamethylcyclopentene measured in mineral acid and formic and acetic acid buffer solutions show general acid catalysis and give large kinetic isotope effects in the normal direction (kH/kD > 1). This indicates that these reactions proceed by the conventional mechanism for vinyl ether hydrolysis in which proton transfer from the catalyzing acid to the substrate is rate-determining, and that the I-strain in these substrates is insufficiently great to shift the reaction mechanism to rapidly reversible substrate protonation followed by rate-determining hydration of the ensuing cationic intermediate.

AN INVERSE HYDROGEN ISOTOPE EFFECT IN THE HYDROLYSIS OF SODIUM BOROHYDRIDE1,2

1960 ◽  
Vol 82 (22) ◽  
pp. 5950-5951 ◽  
Author(s):  
Robert Earl Davis ◽  
Charles L. Kibby ◽  
C. Gardner Swain
Keyword(s):  
Isotope Effect ◽  
Hydrogen Isotope ◽  
Hydrogen Isotope Effect ◽  
Hydrolysis Of

scholarly journals pH Dependent Mechanisms of Hydrolysis of 4-Nitrophenyl β-D-Glucoside

2021 ◽  
Author(s):  
Amani Alhifthi ◽  
Spencer Williams
Keyword(s):  
Isotope Effect ◽  
Nucleophilic Aromatic Substitution ◽  
Aromatic Substitution ◽  
Solvent Isotope Effect ◽  
Dissociative Mechanism ◽  
Neighboring Group ◽  
Rate Determining Step ◽  
Solvent Isotope ◽  
A Minor ◽  
Hydrolysis Of

1,2-<i>trans</i>-Glycosides hydrolyze through different mechanisms at different pH values, but systematic studies are lacking. Here we report the pH-rate constant profile for the hydrolysis of<i> </i>4-nitrophenyl β-D-glucoside. An inverse kinetic isotope effect (<i>k</i>(H<sub>3</sub>O<sup>+</sup>)/<i>k</i>(D<sub>3</sub>O<sup>+</sup>) = 0.63) in the acidic region indicates that the mechanism requires the formation of the conjugate acid of the substrate for the reaction to proceed, with heterolytic cleavage of the glycosidic C-O bond. Reactions in the pH-independent region exhibit general catalysis with a single proton in flight, a normal solvent isotope effect of <i>k</i><sub>H</sub>/<i>k</i><sub>D</sub> = 1.5, and when extrapolated to zero buffer concentration show a small solvent isotope effect <i>k</i>(H<sub>2</sub>O)/<i>k</i>(D<sub>2</sub>O) = 1.1, consistent with water attack through a dissociative mechanism. In the basic region, solvolysis in <sup>18</sup>O-labelled water and H<sub>2</sub>O/MeOH mixtures allowed detection of bimolecular hydrolysis and neighboring group participation, with a minor contribution of nucleophilic aromatic substitution. Under mildly basic conditions, a bimolecular concerted mechanism is implicated through an inverse solvent isotope effect of <i>k</i>(HO<sup>–</sup>)/<i>k</i>(DO<sup>–</sup>) = 0.5 and a strongly negative entropy of activation (D<i>S</i><sup>‡</sup> = –13.6 cal mol<sup>–1</sup> K<sup>–1</sup>). Finally, at high pH, an inverse solvent isotope effect of <i>k</i>(HO<sup>–</sup>)/<i>k</i>(DO<sup>–</sup>) = 0.6 indicates that the formation of 1,2-anhydrosugar is the rate determining step.<br>

scholarly journals pH Dependent Mechanisms of Hydrolysis of 4-Nitrophenyl β-D-Glucoside

2021 ◽  
Author(s):  
Amani Alhifthi ◽  
Spencer Williams
Keyword(s):  
Isotope Effect ◽  
Nucleophilic Aromatic Substitution ◽  
Aromatic Substitution ◽  
Solvent Isotope Effect ◽  
Dissociative Mechanism ◽  
Neighboring Group ◽  
Rate Determining Step ◽  
Solvent Isotope ◽  
A Minor ◽  
Hydrolysis Of

1,2-<i>trans</i>-Glycosides hydrolyze through different mechanisms at different pH values, but systematic studies are lacking. Here we report the pH-rate constant profile for the hydrolysis of<i> </i>4-nitrophenyl β-D-glucoside. An inverse kinetic isotope effect (<i>k</i>(H<sub>3</sub>O<sup>+</sup>)/<i>k</i>(D<sub>3</sub>O<sup>+</sup>) = 0.63) in the acidic region indicates that the mechanism requires the formation of the conjugate acid of the substrate for the reaction to proceed, with heterolytic cleavage of the glycosidic C-O bond. Reactions in the pH-independent region exhibit general catalysis with a single proton in flight, a normal solvent isotope effect of <i>k</i><sub>H</sub>/<i>k</i><sub>D</sub> = 1.5, and when extrapolated to zero buffer concentration show a small solvent isotope effect <i>k</i>(H<sub>2</sub>O)/<i>k</i>(D<sub>2</sub>O) = 1.1, consistent with water attack through a dissociative mechanism. In the basic region, solvolysis in <sup>18</sup>O-labelled water and H<sub>2</sub>O/MeOH mixtures allowed detection of bimolecular hydrolysis and neighboring group participation, with a minor contribution of nucleophilic aromatic substitution. Under mildly basic conditions, a bimolecular concerted mechanism is implicated through an inverse solvent isotope effect of <i>k</i>(HO<sup>–</sup>)/<i>k</i>(DO<sup>–</sup>) = 0.5 and a strongly negative entropy of activation (D<i>S</i><sup>‡</sup> = –13.6 cal mol<sup>–1</sup> K<sup>–1</sup>). Finally, at high pH, an inverse solvent isotope effect of <i>k</i>(HO<sup>–</sup>)/<i>k</i>(DO<sup>–</sup>) = 0.6 indicates that the formation of 1,2-anhydrosugar is the rate determining step.<br>

scholarly journals Vinyl ether hydrolysis. XXIII. Solvent isotope effect on the reaction of divinyl ether catalyzed by the hydronium ion

1990 ◽  
Vol 68 (12) ◽  
pp. 2129-2130 ◽  
Author(s):  
A. J. Kresge ◽  
M. Leibovitch
Keyword(s):  
Vinyl Ether ◽  
Isotope Effect ◽  
Perchloric Acid ◽  
Divinyl Ether ◽  
Solvent Isotope Effect ◽  
Hydronium Ion ◽  
Solvent Isotope ◽  
Hydrolysis Of

Rates of hydrolysis of divinyl ether (CH2=CHOCH=CH2), measured in dilute H2O and D2O solutions of perchloric acid at 25 °C, provide the catalytic coefficients kH+ = 0.0084 M−1 s−1 and kD+ = 0.0028 M−1 s−1, and these lead to the isotope effect kH/kD = 3.0. The magnitude of this isotope effect indicates that this reaction occurs by rate-determining hydron transfer from catalyst to substrate and thus follows the conventional mechanism for vinyl ether hydrolysis. Keywords: divinyl ether, vinyl ether hydrolysis, solvent isotope effect.

scholarly journals pH Dependent Mechanisms of Hydrolysis of 4-Nitrophenyl β-D-Glucoside

2021 ◽  
Author(s):  
Amani Alhifthi ◽  
Spencer Williams
Keyword(s):  
Isotope Effect ◽  
Nucleophilic Aromatic Substitution ◽  
Aromatic Substitution ◽  
Solvent Isotope Effect ◽  
Dissociative Mechanism ◽  
Neighboring Group ◽  
Rate Determining Step ◽  
Solvent Isotope ◽  
A Minor ◽  
Hydrolysis Of

1,2-<i>trans</i>-Glycosides hydrolyze through a range of mechanisms under conditions of different pH, but systematic studies are lacking. Here we report the pH-rate constant profile for the hydrolysis of<i> </i>4-nitrophenyl β-D-glucoside. An inverse kinetic isotope effect (<i>k</i>(H<sub>3</sub>O<sup>+</sup>)/<i>k</i>(D<sub>3</sub>O<sup>+</sup>) = 0.63) in the acidic region indicates that the mechanism requires the formation of the conjugate acid of the substrate for the reaction to proceed, with heterolytic cleavage of the glycosidic C-O bond. Reactions in the pH-independent region exhibited general catalysis with a single proton in flight with a normal solvent isotope effect of <i>k</i><sub>H</sub>/<i>k</i><sub>D</sub> = 1.5, and when extrapolated to zero buffer concentration show a small solvent isotope effect <i>k</i>(H<sub>2</sub>O)/<i>k</i>(D<sub>2</sub>O) = 1.1, which is consistent with water attack through a dissociative mechanism. In the basic region, solvolysis in <sup>18</sup>O-labelled water and H<sub>2</sub>O/MeOH mixtures allowed detection of bimolecular hydrolysis and neighboring group participation, and to a minor degree, nucleophilic aromatic substitution. Under mildly basic conditions, a bimolecular dissociative mechanism is implicated through an inverse solvent isotope effect of <i>k</i>(HO<sup>–</sup>)/<i>k</i>(DO<sup>–</sup>) = 0.5 and a strongly negative entropy of activation (delta<i>S</i><sup>‡</sup> = –13.6 cal mol<sup>–1</sup> K<sup>–1</sup>). Finally, at high pH, an inverse solvent isotope effect of <i>k</i>(HO<sup>–</sup>)/<i>k</i>(DO<sup>–</sup>) = 0.6 indicates that the formation of 1,2-anhydrosugar is the rate determining step.<br>

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