Kinetic Evidence for Predominant Oxygen Protonation of Amides

1972 ◽  
Vol 50 (5) ◽  
pp. 771-773 ◽  
Author(s):  
Clinton R. Smith ◽  
Keith Yates
Keyword(s):  
Strong Evidence ◽  
Rate Data ◽  
Model Compounds ◽  
Recent Proposal ◽  
Acid Catalyzed ◽  
Hydrolysis Of

Comparison of rate data for the acid-catalyzed hydrolysis of amides, and model compounds for O- and N-protonated amides, provides strong evidence that amides protonate predominantly on oxygen in dilute as well as in concentrated aqueous acids, contrary to a recent proposal that the protonation sites are different in the two media.

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 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).

Base-catalyzed Degradations of Carbohydrates. IX. β-Eliminations of 4-O-Substituted Hexopyranosiduronates

1975 ◽  
Vol 53 (14) ◽  
pp. 2182-2188 ◽  
Author(s):  
Gerald O. Aspinall ◽  
Thinnayam N. Krishnamurthy ◽  
Walter Mitura ◽  
Masuo Funabashi
Keyword(s):  
Acid Hydrolysis ◽  
Reducing Sugars ◽  
Model Compounds ◽  
Methyl Methyl ◽  
Hydrolysis Of

Two methylated disaccharides, methyl [methyl 4-O-(2,3,4,6-tetra-O-methyl-α-D-glucopyranosyl)-2,3-di-O-methyl-β-D-glucopyranosid]uronate (9) and methyl 6-O-(methyl 2,3,4-tri-O-methyl-α-D-galactopyranosyluronate)-2,3,4-tri-O-methyl-β-D-glucopyranoside (15) have been synthesized and used as model compounds for the study of the base-catalyzed β-elimination of 4-O-substituted hexopyranosiduronates without degradation of exposed reducing sugars and of the selective acid hydrolysis of hex-4-enopyranosiduronates.

Characteristics of Solid Super Acid SO42-/TiO2-Al2O3-SnO2 during Conversion of Glucose to Levulinic Acid

2012 ◽  
Vol 550-553 ◽  
pp. 103-106
Author(s):  
Ying Liu ◽  
Lu Lin ◽  
Xiao Yu Sui ◽  
Jun Ping Zhuang ◽  
Chun Sheng Pang
Keyword(s):  
Binding Energy ◽  
Levulinic Acid ◽  
Diffraction Peak ◽  
Catalyst Amount ◽  
Hydroxymethyl Furfural ◽  
Good Catalytic Activity ◽  
Super Acid ◽  
Diffraction Peaks ◽  
Acid Catalyzed ◽  
Hydrolysis Of

The effects of catalyst amount on the yields of levulinic and hydroxymethyl furfural were investigated during conversion of glucose to levulinic acid catalyzed by solid super acid SO42- / TiO2-Al2O3-SnO2. XRD and XPS were used to analyse the characteristics of solid super acid SO42- / TiO2-Al2O3-SnO2 before reaction and after reaction. The results showed that: solid super acid SO42- / TiO2-Al2O3-SnO2exhibited good catalytic activity in the reaction of hydrolysis of glucose to produce levulinic acid. There were three obvious peaks in these XRD spectra. The peaks on 44.6° and 67.1° were the characteristic diffraction peaks of γ-Al2O3. The anatase characteristic diffraction peak was on 37.4°. The catalyst was steady in the process. The binding energy of S 2p was similar to the binding energy of standard S6+ 2p in the S 2p XPS spectrum of solid super acid. O 1s XPS was double-peaked spectrum. The increase of element C was the main reason of inactivation of catalyst.

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