Mechanisms of alkaline degradation of sucrose. Relative rates of alkaline degradation of some sucrose derivatives

An earlier study of the relative rates of degradation of several sucrose derivatives has been refined and extended. The results support a novel hypothesis to explain the unusual alkali-lability of sucrose (1). In this hypothesis the first and rate-determining step in the degradation is an SN1cB displacement effected at the C1 anomeric centre of the glucose moiety by an oxyanion derived from the C1' hydroxyl (10), to produce 1-(α-D-glucopyranosyl)fructose (11). The latter is then very rapidly degraded, mainly to lactic acid. The possibility of analogous competing displacements involving the 3' and 6' oxyanions remains for further investigation.

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MODELING AND OPTIMIZATION OF LACTIC ACID SYNTHESIS BY THE ALKALINE DEGRADATION OF FRUCTOSE IN A BATCH REACTOR

Chemical Engineering Communications ◽

10.1080/009864490519852 ◽

2005 ◽

Vol 192 (6) ◽

pp. 758-786 ◽

Cited By ~ 5

Author(s):

M. Cabassud ◽

P. Cognet ◽

V. Garcia ◽

M. V. LE LANN ◽

G. Casamatta ◽

...

Keyword(s):

Lactic Acid ◽

Batch Reactor ◽

Acid Synthesis ◽

Alkaline Degradation ◽

Modeling And Optimization

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Chromic oxidation of lactic acid in very strong acid media

Canadian Journal of Chemistry ◽

10.1139/v90-007 ◽

1990 ◽

Vol 68 (1) ◽

pp. 29-32 ◽

Cited By ~ 4

Author(s):

María Piedad Alvarez-Macho ◽

María Isabel Montequi-Martin

Keyword(s):

Lactic Acid ◽

Chromic Acid ◽

Strong Acid ◽

Mineral Acid ◽

Acid Oxidation ◽

Acid Media ◽

Chromic Acid Oxidation ◽

Rate Determining Step ◽

Entropy Of Activation ◽

High Concentrations

The oxidation of lactic acid by chromic acid was studied at high concentrations of HClO4, HNO3, and H2SO4. It was observed that the reaction rate depends not only on the acidity of the medium, but also on the nature of the mineral acid. The use of the Bunnett and Bunnett–Olsen criteria and the excess acidity concept allows us to propose a reaction mechanism of the A-2 type, the rate-determining step being a bimolecular process in which water participates as a nucleophile. The enthalpy and entropy of activation were determined; the decrease of the magnitude of these parameters when the acidity of the medium was increased suggests the existence of a compensation effect. Keywords: chromic acid, oxidation, lactic acid, acidic media.

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Kinetic and Mechanistic Study of the Reduction of Chromium(VI) by Lactic Acid

Research Letters in Inorganic Chemistry ◽

10.1155/2008/314045 ◽

2008 ◽

Vol 2008 ◽

pp. 1-4 ◽

Cited By ~ 4

Author(s):

Jinhuan Shan ◽

Fang Wang ◽

Changying Song ◽

Heye Wang

Keyword(s):

Lactic Acid ◽

Rate Constant ◽

Activation Parameters ◽

Mechanistic Study ◽

First Order ◽

Chromium Vi ◽

Rate Determining Step ◽

Probable Reaction Mechanism ◽

Probable Reaction ◽

Aqueous Acidic Medium

The kinetics and mechanism of the reduction of chromium(VI) by lactic acid (Lac) in aqueous acidic medium was studied with spectrophotometry in a temperature range of 298.15 K~313.15 K. Under the conditions of the pseudo-first order , the observed rate constant increased with the increase in [Lac] and . There is no salt effect. Based on the experimental results, a probable reaction mechanism of oxidation was proposed. The rate equation derived from the mechanism could explain all the experimental phenomena. Activation parameters along with rate constant of the rate-determining step have been evaluated.

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Mechanism of alkaline degradation of sucrose. A study of some model compounds

Australian Journal of Chemistry ◽

10.1071/ch9732041 ◽

1973 ◽

Vol 26 (9) ◽

pp. 2041 ◽

Cited By ~ 7

Author(s):

GW O'Donnell ◽

GN Richards

Keyword(s):

Gas Chromatography ◽

Lactic Acid ◽

Reactive Intermediates ◽

Hydroxyl Groups ◽

Alkaline Degradation ◽

Model Compounds ◽

Free Hydroxyl

Alkaline degradation of sucrose proceeds by a slow first stage to yield reactive intermediates (perhaps glucose and fructose) which degrade rapidly to acids (predominantly lactic acid). In an attempt to determine the mechanism of the first stage of the reaction, the rates of alkaline degradation of sucrose and some model compounds have been determined unequivocally by measuring their rates of disappearance by paper or gas chromatography. Selective blocking of hydroxyl groups in sucrose by methylation, indicates that the alkaline degradation probably involves free hydroxyl groups (presumably via the derived anions) on both glucose and fructose components of sucrose. It is unlikely that the hydroxyls at C 6 of the glucose moiety or C 1? of the fructose moiety are involved.

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A global Strategy for the Optimization of Batch Reactors: Application to the Lactic Acid Synthesis by the Alkaline Degradation of Fructose

IFAC Proceedings Volumes ◽

10.1016/s1474-6670(17)44410-7 ◽

1997 ◽

Vol 30 (5) ◽

pp. 63-68 ◽

Cited By ~ 1

Author(s):

V. Garcia ◽

M. Cabassud ◽

M.V. Le Lann ◽

G. Casamatta ◽

L. Rigal

Keyword(s):

Lactic Acid ◽

Acid Synthesis ◽

Global Strategy ◽

Batch Reactors ◽

Alkaline Degradation

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Demonstration of Retinal Glycogen with Silver Methenamine

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100066875 ◽

1971 ◽

Vol 29 ◽

pp. 564-565

Author(s):

A. W. Sedar ◽

G. H. Bresnick

Keyword(s):

Lactic Acid ◽

Chromic Acid ◽

Periodic Acid ◽

Müller Cell ◽

External Limiting Membrane ◽

Electron Microscope Level ◽

Reactive Process ◽

Inner Limiting Membrane ◽

Muller Cell ◽

And Migration

After experimetnal damage to the retina with a variety of procedures Müller cell hypertrophy and migration occurs. According to Kuwabara and others the reactive process in these injuries is evidenced by a marked increase in amount of glycogen in the Müller cells. These cells were considered originally supporting elements with fiber processes extending throughout the retina from inner limiting membrane to external limiting membrane, but are known now to have high lactic acid dehydrogenase activity and the ability to synthesize glycogen. Since the periodic acid-chromic acid-silver methenamine technique was shown to demonstrate glycogen at the electron microscope level, it was selected to react with glycogen in the fine processes of the Müller cell that ramify among the neural elements in various layers of the retina and demarcate these cells cytologically. The Rhesus monkey was chosen as an example of a well vascularized retina and the rabbit as an example of a avascular retina to explore the possibilities of the technique.

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