Practical Synthesis of β-Ketothioesters by Acid-Catalyzed Hydrolysis of Ketene N,S -Acetals with Amino as the Leaving Group

2019 ◽  
Vol 2019 (22) ◽  
pp. 3704-3710 ◽  
Author(s):  
Qi Xu ◽  
Baihui Zheng ◽  
Ling Pan ◽  
Qun Liu ◽  
Yifei Li
Keyword(s):  
Leaving Group ◽  
Practical Synthesis ◽  
Acid Catalyzed ◽  
Hydrolysis Of

Mechanism and Stereochemistry of the Hydrolysis of 4-Arylamino-1,2,3,4- tetrahydroquinaldines

1974 ◽  
Vol 52 (6) ◽  
pp. 884-887 ◽  
Author(s):  
T. P. Forrest ◽  
G. A. Dauphinee ◽  
W. F. Miles
Keyword(s):  
Nitrogen Atom ◽  
Equilibrium Mixture ◽  
Hydroxyl Group ◽  
Amino Group ◽  
Heterocyclic Nitrogen ◽  
Carbonium Ion ◽  
Kinetically Controlled ◽  
Leaving Group ◽  
Acid Catalyzed ◽  
Hydrolysis Of

Rates of acid-catalyzed hydrolysis of the benzylic amino group in stereoisomers of 4-arylamino-1,2,3,4-tetrahydroquinaldines have been determined by n.m.r. spectroscopy. Those isomers which have a pseudo-axial leaving group react more rapidly than those with a pseudo-equatorial leaving group, forming in each case the isomer with a pseudo-axial hydroxyl group as the kinetically controlled product. This product is converted in time to an equilibrium mixture of the two stereoisomeric alcohols. The reaction is inhibited by excess acid and appears to proceed through an intermediate carbonium ion which is stabilized by the heterocyclic nitrogen atom.

Allylic Amination via Acid Catalyzed Leaving Group Activation

2016 ◽  
Vol 3 (2) ◽  
pp. 145-159
Author(s):  
Marija Skvorcova ◽  
Aigars Jirgensons
Keyword(s):  
Allylic Amination ◽  
Leaving Group ◽  
Acid Catalyzed

The effect of polymeric and model imidazolium halides on the rate of hydrolysis of 4-acetoxy-3-nitrobenzoic acid

1985 ◽  
Vol 50 (4) ◽  
pp. 845-853 ◽  
Author(s):  
Miloslav Šorm ◽  
Miloslav Procházka ◽  
Jaroslav Kálal
Keyword(s):  
Catalyst Concentration ◽  
Low Molecular Weight ◽  
Imidazolium Chloride ◽  
First Order ◽  
Nitrobenzoic Acid ◽  
Rate Of Hydrolysis ◽  
Acid Catalyzed ◽  
Hydrolysis Of ◽  
Ethanol In Water ◽  
Direct Attack

The course of hydrolysis of an ester, 4-acetoxy-3-nitrobenzoic acid catalyzed with poly(1-methyl-3-allylimidazolium bromide) (IIa), poly[l-methyl-3-(2-propinyl)imidazolium chloride] (IIb) and poly[l-methyl-3-(2-methacryloyloxyethyl)imidazolium bromide] (IIc) in a 28.5% aqueous ethanol was investigated as a function of pH and compared with low-molecular weight models, viz., l-methyl-3-alkylimidazolium bromides (the alkyl group being methyl, propyl, and hexyl, resp). Polymers IIb, IIc possessed a higher activity at pH above 9, while the models were more active at a lower pH with a maximum at pH 7.67. The catalytic activity at the higher pH is attributed to an attack by the OH- group, while at the lower pH it is assigned to a direct attack of water on the substrate. The rate of hydrolysis of 4-acetoxy-3-nitrobenzoic acid is proportional to the catalyst concentration [IIc] and proceeds as a first-order reaction. The hydrolysis depends on the composition of the solvent and was highest at 28.5% (vol.) of ethanol in water. The hydrolysis of a neutral ester, 4-nitrophenyl acetate, was not accelerated by IIc.

Benzyl ethers of methyl α-D-glucopyranoside

1980 ◽  
Vol 45 (7) ◽  
pp. 1959-1963 ◽  
Author(s):  
Dušan Joniak ◽  
Božena Košíková ◽  
Ludmila Kosáková
Keyword(s):  
Kinetic Study ◽  
Spectrophotometric Determination ◽  
Reductive Cleavage ◽  
Ether Bond ◽  
Benzyl Ethers ◽  
Acid Catalyzed ◽  
Model Substances ◽  
Hydrolysis Of

Methyl 4-O-(3-methoxy-4-hydroxybenzyl) and methyl 4-O-(3,5-dimethoxy-4-hydroxybenzyl)-α-D-glucopyranoside and their 6-O-isomers were prepared as model substances for the ether lignin-saccharide bond by reductive cleavage of corresponding 4,6-O-benzylidene derivatives. Kinetic study of acid-catalyzed hydrolysis of the compounds prepared was carried out by spectrophotometric determination of the benzyl alcoholic groups set free, after their reaction with quinonemonochloroimide, and it showed the low stability of the p-hydroxybenzyl ether bond.

Cyclization and acid-catalyzed hydrolysis of O-benzoylbenzamidoximes

1986 ◽  
Vol 51 (12) ◽  
pp. 2786-2797
Author(s):  
František Grambal ◽  
Jan Lasovský
Keyword(s):  
Reaction Rate ◽  
Kinetic Isotope ◽  
Acid Base Equilibrium ◽  
Mineral Acids ◽  
Kinetics Of Formation ◽  
Acid Catalyzed ◽  
Ph Scale ◽  
Kinetics Of ◽  
Hydrolysis Of ◽  
Derivatives Of

Kinetics of formation of 1,2,4-oxadiazoles from 24 substitution derivatives of O-benzoylbenzamidoxime have been studied in sulphuric acid and aqueous ethanol media. It has been found that this medium requires introduction of the Hammett H0 function instead of the pH scale beginning as low as from 0.1% solutions of mineral acids. Effects of the acid concentration, ionic strength, and temperature on the reaction rate and on the kinetic isotope effect have been followed. From these dependences and from polar effects of substituents it was concluded that along with the cyclization to 1,2,4-oxadiazoles there proceeds hydrolysis to benzamidoxime and benzoic acid. The reaction is thermodynamically controlled by the acid-base equilibrium of the O-benzylated benzamidoximes.

scholarly journals Pseudomonas putida MPE, a manganese-dependent endonuclease of the binuclear metallophosphoesterase superfamily, incises single-strand DNA in two orientations to yield a mixture of 3′-PO4 and 3′-OH termini

2020 ◽  
Author(s):  
Shreya Ghosh ◽  
Anam Ejaz ◽  
Lucas Repeta ◽  
Stewart Shuman
Keyword(s):  
Pseudomonas Putida ◽  
Bound Water ◽  
Acid Catalyst ◽  
Nuclease Activity ◽  
Single Strand ◽  
Dna Endonuclease ◽  
Dependent Endonuclease ◽  
Leaving Group ◽  
Phosphodiester Hydrolysis ◽  
Hydrolysis Of

Abstract Pseudomonas putida MPE exemplifies a novel clade of manganese-dependent single-strand DNA endonuclease within the binuclear metallophosphoesterase superfamily. MPE is encoded within a widely conserved DNA repair operon. Via structure-guided mutagenesis, we identify His113 and His81 as essential for DNA nuclease activity, albeit inessential for hydrolysis of bis-p-nitrophenylphosphate. We propose that His113 contacts the scissile phosphodiester and serves as a general acid catalyst to expel the OH leaving group of the product strand. We find that MPE cleaves the 3′ and 5′ single-strands of tailed duplex DNAs and that MPE can sense and incise duplexes at sites of short mismatch bulges and opposite a nick. We show that MPE is an ambidextrous phosphodiesterase capable of hydrolyzing the ssDNA backbone in either orientation to generate a mixture of 3′-OH and 3′-PO4 cleavage products. The directionality of phosphodiester hydrolysis is dictated by the orientation of the water nucleophile vis-à-vis the OH leaving group, which must be near apical for the reaction to proceed. We propose that the MPE active site and metal-bound water nucleophile are invariant and the enzyme can bind the ssDNA productively in opposite orientations.

scholarly journals Application of Polyimide‐based Microfluidic Devices on Acid‐catalyzed Hydrolysis of Dimethoxypropane

2021 ◽  
Vol 93 (5) ◽  
pp. 796-801
Author(s):  
Jens Bobers ◽  
Elisabeth Forys ◽  
Bastian Oldach ◽  
Norbert Kockmann
Keyword(s):  
Microfluidic Devices ◽  
Acid Catalyzed ◽  
Hydrolysis Of

A kinetic standard for precise calibration of spectrophotometer cell temperature.

1981 ◽  
Vol 27 (5) ◽  
pp. 753-755 ◽  
Author(s):  
P A Adams ◽  
M C Berman
Keyword(s):  
Temperature Dependence ◽  
Rate Constants ◽  
Cell Temperature ◽  
First Order ◽  
Order Rate ◽  
Acid Catalyzed ◽  
Pseudo First Order ◽  
Hydrolysis Of

Abstract We describe a simple, highly reproducible kinetic technique for precisely measuring temperature in spectrophotometric systems having reaction cells that are inaccessible to conventional temperature probes. The method is based on the temperature dependence of pseudo-first-order rate constants for the acid-catalyzed hydrolysis of N-o-tolyl-D-glucosylamine. Temperatures of reaction cuvette contents are measured with a precision of +/- 0.05 degrees C (1 SD).

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