Micellar Catalysis of Organic Reactions. XXXVIII A Study of the Catalytic Effect of Micelles of 3-Hydroxymethyl-1-tetradecylpyridinium Bromide on Amide Hydrolysis and Nucleophilic Aromatic Substitution

1998 ◽  
Vol 51 (7) ◽  
pp. 541 ◽  
Author(s):  
Trevor J. Broxton
Keyword(s):  
Catalytic Effect ◽  
Micellar Catalysis ◽  
Aryl Halides ◽  
Organic Reactions ◽  
Nucleophilic Aromatic Substitution ◽  
Aromatic Substitution ◽  
Rate Determining Step ◽  
Amide Hydrolysis

The preparation of 3-hydroxymethyl-1-tetradecylpyridinium bromide and its use as a catalyst of nucleophilic aromatic substitution and also amide hydrolysis are reported. It was found that the hydroxydehalogenation of nitro-activated aryl halides was much faster in these micelles than in the presence of cetyl(2-hydroxyethyl)dimethylammonium bromide. It was concluded that the increased catalysis of nucleophilic aromatic substitution by this micelle was due to a faster decomposition of the aryl micellar ether which must occur before the phenolate product is released. No such difference in the two micelles was found for amide or thioamide hydrolysis since in these reactions the product amine is produced in the first step of the reaction and decomposition of the acylated micelle is not required in the rate-determining step of the reaction.

Micellar catalysis of organic reactions. IX. The reaction of sodium azide with activated aromatic halides and the subsequent decomposition of the initially formed aryl azide

1982 ◽  
Vol 35 (12) ◽  
pp. 2557 ◽  
Author(s):  
TJ Broxton ◽  
AC Jakovljevic
Keyword(s):  
Sodium Azide ◽  
Substitution Reaction ◽  
Cetyltrimethylammonium Bromide ◽  
Micellar Catalysis ◽  
Organic Reactions ◽  
Nucleophilic Aromatic Substitution ◽  
Aromatic Substitution ◽  
Aryl Azide ◽  
Snar Reaction ◽  
Subsequent Decomposition

The effect of micelles of cetyltrimethylammonium bromide on the SNAr reaction of azide ions with 1-halogeno-2,4-dinitrobenzenes and on the subsequent decomposition of the aryl azide product has been measured. The nucleophilic aromatic substitution reaction is shown to be subject to significant micellar catalysis whereas the subsequent decomposition of the aryl azide is not.

Nucleophilic Aromatic Substitution Reactions in Water Enabled by Micellar Catalysis

2015 ◽  
Vol 17 (19) ◽  
pp. 4734-4737 ◽  
Author(s):  
Nicholas A. Isley ◽  
Roscoe T. H. Linstadt ◽  
Sean M. Kelly ◽  
Fabrice Gallou ◽  
Bruce H. Lipshutz
Keyword(s):  
Micellar Catalysis ◽  
Nucleophilic Aromatic Substitution ◽  
Aromatic Substitution ◽  
Substitution Reactions

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 Unimolecular, bimolecular and intramolecular hydrolysis mechanisms of 4-nitrophenyl β-D-glucopyranoside

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 ◽  
Conjugate Acid ◽  
Solvent Isotope ◽  
A Minor

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 of <i>k</i>(H<sub>3</sub>O<sup>+</sup>)/<i>k</i>(D<sub>3</sub>O<sup>+</sup> = 0.65 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>

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