Enolization and Oxidation Reactions of Reducing Sugars

1973 ◽  
pp. 70-87 ◽  
Author(s):  
HORACE S. ISBELL
Keyword(s):  
Reducing Sugars ◽  
Oxidation Reactions

scholarly journals MISCONCEPTIONS IN THE CHEMISTRY TEACHING IN THE REPUBLIC OF MACEDONIA REGARDING THE OXIDATION REACTIONS OF MONOSACCHARIDES

2017 ◽  
Vol 34 (1-2) ◽  
Author(s):  
Marina Stojanovska ◽  
Bojan Šoptrajanov ◽  
Vladimir M. Petruševski
Keyword(s):  
Reducing Sugars ◽  
Reaction System ◽  
Oxidation Reactions ◽  
Chemistry Teaching ◽  
Oxidizing Agents ◽  
Republic Of Macedonia ◽  
Alkaline Conditions ◽  
The Republic ◽  
Aldehyde Groups

The easy oxidation of the substances containing aldehyde groups using a mild oxidizing agents, such as solutions containing copper(II) or silver(I) ions, can provide a mean to detect the presence of carbohydrates known as reducing sugars. However, using such tests, it is not possible to distinguish between aldoses and ketoses because the alkaline conditions in the reaction system lead to tautomerization of the α-hidroxyketone and immediate oxidation of the product so that both glucose and fructose will react with the oxidizing agents (the Tollens’ and Fehling’s reagents). In fact, the reaction of fructose is even faster than that of glucose. A misinterpretation or simple neglect of these experimental facts is present in some textbooks in the Republic of Macedonia and this influences the chemistry teaching by creating misconceptions among students and teachers.

QUALITATIVE AND QUANTITATIVE PHYTOCHEMICAL SCREENING AND IN VITRO ANTIOXIDANT EVALUATION OF PERGULARIA DAEMIA

2018 ◽  
Vol 24 (2) ◽  
Author(s):  
GITA MISHRA ◽  
HEMESHWER KUMAR CHANDRA ◽  
NISHA SAHU ◽  
SATENDRA KUMAR NIRALA ◽  
MONIKA BHADAURIA
Keyword(s):  
Reducing Sugars ◽  
Antioxidant Properties ◽  
Phytochemical Analysis ◽  
Phytochemical Screening ◽  
Qualitative And Quantitative ◽  
The Family ◽  
Ethanolic Extracts ◽  
Antioxidant Evaluation ◽  
In Vitro Antioxidant Activity

Pergularia daemia belongs to the family Asclepiadaceae, known to have anticancer, anti-inflammatory activity. Aim of the present study was to evaluate qualitative and quantitative phytochemical and antioxidant properties of ethanolic extracts of leaf, stem and root parts of P. daemia . Preliminary phytochemical analysis and in vitro antioxidant properties were evaluated by standard methods. The qualitative phytochemical analysis of P. daemia showed presence of flavonoids, tannins, alkaloid, phytosterol, carbohydrate, phenol, saponin, glycosides, terpenoids, steroids proteins and reducing sugars. Quantitative analysis showed polyphenol, flavonoid, flavonone, flavone and flavonol in P. daemia leaves, stem and root in considerable quantity. The in vitro antioxidant activity of P. daemia clearly demonstrated that leaf, stem and root parts have prominent antioxidant properties and was effective in scavenging free radicals.

Mechanism of Oxidation Reactions of Bromine

1958 ◽  
Vol 14 (5_6) ◽  
pp. 357-360
Author(s):  
K. C. Grover ◽  
R. C. Mehrotra
Keyword(s):  
Oxidation Reactions ◽  
Mechanism Of Oxidation

Mechanism of Oxidation Reactions of Bromine

1958 ◽  
Vol 14 (5_6) ◽  
pp. 345-356 ◽  
Author(s):  
K. C. Grover ◽  
R. C. Mehrotra
Keyword(s):  
Oxidation Reactions ◽  
Mechanism Of Oxidation

Effects Attributed to Maleic Hydrazide when used for Chemical Sucker Control on Bright Tobacco

1980 ◽  
Vol 10 (2) ◽  
Author(s):  
Heinz Seltmann
Keyword(s):  
Statistical Difference ◽  
Reducing Sugars ◽  
Maleic Hydrazide ◽  
Water Soluble ◽  
Total Volatile ◽  
Total Alkaloids ◽  
Group I ◽  
Excellent Control ◽  
Per Se ◽  
Group Ii

AbstractThe effect of maleic hydrazide (MH) per se on bright tobacco was determined by comparing plants treated with MH to those without MH under conditions of good chemical sucker control. Sequential applications of each of five contact-type agents with MH one week later (Group I) were compared to dual applications of each of the same contact agents (Group II). In Group II suckers missed during applications were individually wetted to ensure excellent control. Sucker control was measured as 95 % for Group I and assumed to be 99 % for Group II. There were no agronomic differences between Groups I and II. In the visual warehouse appraisal, there was only a statistical difference for thin-bodied tobaccos between the two groups and a trend for slightly more heavy-bodied tobaccos in Group I. The chemical and physical analyses showed that filling value at 13 % moisture and equilibrium moisture content (EMC) measured at 60 % relative humidity were significantly lower in Group I than Group II. The result for EMC was questioned. Actual values for total alkaloids, total volatile bases minus nicotine, total ash, and alkalinity number of water-soluble ash were lower and reducing sugars were higher where MH was used. Except for EMC, the findings in this study reflected those established in studies where MH-treated and normally hand-suckered tobaccos were compared, but the differences here were generally not as great.

Thermo-Oxidative Decomposition of Lovage (Levisticum officinale) and Davana (Artemisia pallens) Essential Oils under Simulated Tobacco Heating Product Conditions

2020 ◽  
Vol 29 (1) ◽  
pp. 27-43
Author(s):  
Emma Jakab ◽  
Zoltán Sebestyén ◽  
Bence Babinszki ◽  
Eszter Barta-Rajnai ◽  
Zsuzsanna Czégény ◽  
...  
Keyword(s):  
Low Temperature ◽  
Essential Oils ◽  
Relative Yield ◽  
Gas Chromatography Mass Spectrometry ◽  
Intramolecular Rearrangement ◽  
Oxidation Reactions ◽  
Pyrolysis Gas ◽  
Oxidative Decomposition ◽  
Oxidative Pyrolysis ◽  
Artemisia Pallens

SummaryThe thermo-oxidative decomposition of lovage (Levisticum officinale) and davana (Artemisia pallens) essential oils has been studied by pyrolysis-gas chromatography/mass spectrometry in 9% oxygen and 91% nitrogen atmosphere at 300 °C to simulate low-temperature tobacco heating conditions. Both lovage and davana oils contain numerous chemical substances; the main components of both oils are various oxygen-containing compounds. Isobenzofuranones are the most important constituents of lovage oil, and their relative intensity changed significantly during oxidative pyrolysis. (Z)-ligustilide underwent two kinds of decomposition reactions: an aromatization reaction resulting in the formation of butylidenephthalide and the scission of the lactone ring with the elimination of carbon dioxide or carbon monoxide. Davanone is the main component of davana oil, which did not decompose considerably during low-temperature oxidative pyrolysis. However, the relative yield of the second most intensive component, bicyclogermacrene, reduced markedly due to bond rearrangement reactions. Davana ether underwent oxidation reactions leading to the formation of various furanic compounds. The changes in the composition of both essential oils could be interpreted in terms of bond splitting, intramolecular rearrangement mechanisms and oxidation reactions of several constituents during low-temperature oxidative pyrolysis. The applied thermo-oxidative method was found to be suitable to study the stability of the essential oils and monitor the decomposition products under simulated tobacco heating conditions. In spite of the complicated composition of the essential oils, no evidence for interaction between the oil components was found. [Beitr. Tabakforsch. Int. 29 (2020) 27–43]

Oxidase Catalysis via an Aerobically Generated Dess-Martin Periodinane Analogue

2018 ◽  
Author(s):  
Asim Maity ◽  
Sung-Min Hyun ◽  
Alan Wortman ◽  
David Powers
Keyword(s):  
Chemical Synthesis ◽  
Aerobic Oxidation ◽  
Substrate Oxidation ◽  
Oxidation Catalysis ◽  
Hypervalent Iodine ◽  
Oxidation Reactions ◽  
Broad Array ◽  
Oxidation Chemistry ◽  
Reactive Oxidants

<p>Hypervalent iodine(V) reagents, such as Dess-Martin periodinane (DMP) and 2-iodoxybenzoic acid (IBX), are broadly useful oxidants in chemical synthesis. Development of strategies to access these reagents from O2 would immediately enable use of O2 as a terminal oxidant in a broad array of substrate oxidation reactions. Recently we disclosed the aerobic synthesis of I(III) reagents by intercepting reactive oxidants generated during aldehyde autoxidation. Here, we couple aerobic oxidation of iodobenzenes with disproportionation of the initially generated I(III) compounds to generate I(V) reagents. The aerobically generated I(V) reagents exhibit substrate oxidation chemistry analogous to that of DMP. Further, the developed aerobic generation of I(V) has enabled the first application of I(V) intermediates in aerobic oxidation catalysis.</p>

Tuning the Activities of Cu2O Nanostructures via the Oxide-Metal Interaction

2019 ◽  
Author(s):  
Wugen Huang ◽  
qingfei liu ◽  
Zhiwen Zhou ◽  
Yangsheng Li ◽  
Yong Wang ◽  
...  
Keyword(s):  
Co Oxidation ◽  
Oxidation Catalysis ◽  
Atomic Scale ◽  
Scanning Tunneling ◽  
Oxidation Reactions ◽  
Tunneling Microscopy ◽  
Temperature Oxidation ◽  
Metal Interaction ◽  
Tremendous Importance ◽  
Oxygen Atoms

Despite tremendous importance in catalysis, the design and improvement of the oxide- metal interface has been hampered by the limited understanding on the nature of interfacial sites, as well as the oxide-metal interaction (OMI). Through the construction of well-defined Cu<sub>2</sub>O-Pt, Cu<sub>2</sub>O-Ag, Cu<sub>2</sub>O-Au interfaces, we found that Cu<sub>2</sub>O Nanostructures (NSs) on Pt exhibit much lower thermal stability than on Ag and Au, although they show the same surface and edge structures, as identified by element-specific scanning tunneling microscopy (ES-STM) images. The activities of the Cu<sub>2</sub>O-Pt and Cu<sub>2</sub>O-Au interfaces for CO oxidation were further compared at the atomic scale and showed in general that the interface with Cu<sub>2</sub>O NSs could annihilate the CO-poisoning problem suffered by Pt group metals and enhance the interaction with O<sub>2</sub>, which is a limiting step for CO oxidation catalysis on group IB metals. While both interfaces could react with CO at room temperature, the OMI was found to determine the reactivity of supported Cu<sub>2</sub>O NSs by 1) tuning the activity of interfacial oxygen atoms and 2) stabilizing oxygen vacancies or vice versa, the dissociated oxygen atoms at the interface. Our study provides new insight for OMI and for the development of Cu-based catalysts for low temperature oxidation reactions.

Tuning the Activities of Cu2O Nanostructures via the Oxide-Metal Interaction

2019 ◽  
Author(s):  
Wugen Huang ◽  
Yangsheng Li ◽  
Yong Wang ◽  
Yunchuan Tu ◽  
Dehui Deng ◽  
...  
Keyword(s):  
Co Oxidation ◽  
Oxidation Catalysis ◽  
Atomic Scale ◽  
Scanning Tunneling ◽  
Oxidation Reactions ◽  
Tunneling Microscopy ◽  
Temperature Oxidation ◽  
Metal Interaction ◽  
Tremendous Importance ◽  
Oxygen Atoms

Despite tremendous importance in catalysis, the design and improvement of the oxide- metal interface has been hampered by the limited understanding on the nature of interfacial sites, as well as the oxide-metal interaction (OMI). Through the construction of well-defined Cu<sub>2</sub>O-Pt, Cu<sub>2</sub>O-Ag, Cu<sub>2</sub>O-Au interfaces, we found that Cu<sub>2</sub>O Nanostructures (NSs) on Pt exhibit much lower thermal stability than on Ag and Au, although they show the same surface and edge structures, as identified by element-specific scanning tunneling microscopy (ES-STM) images. The activities of the Cu<sub>2</sub>O-Pt and Cu<sub>2</sub>O-Au interfaces for CO oxidation were further compared at the atomic scale and showed in general that the interface with Cu<sub>2</sub>O NSs could annihilate the CO-poisoning problem suffered by Pt group metals and enhance the interaction with O<sub>2</sub>, which is a limiting step for CO oxidation catalysis on group IB metals. While both interfaces could react with CO at room temperature, the OMI was found to determine the reactivity of supported Cu<sub>2</sub>O NSs by 1) tuning the activity of interfacial oxygen atoms and 2) stabilizing oxygen vacancies or vice versa, the dissociated oxygen atoms at the interface. Our study provides new insight for OMI and for the development of Cu-based catalysts for low temperature oxidation reactions.

PHYSICOCHEMICAL AND MICROBIOLOGICAL EVALUATION OF HONEYS CONSUMED BY THE ELDERLY

2020 ◽  
Vol 5 ◽  
Author(s):  
Lusmarina Rodrigues Silva ◽  
Aline Marques Monte ◽  
Rafael Gomes Abreu Bacelar ◽  
Guilherme Antonio Silva Ribeiro ◽  
Aline Maria Dourado Rodrigues ◽  
...  
Keyword(s):  
Health Center ◽  
Reducing Sugars ◽  
The Elderly ◽  
Indicator Bacteria ◽  
Foreign Matter ◽  
Total Sugars ◽  
Significant Contamination ◽  
Almost All ◽  
Microbiological Analyses ◽  
Current Standards

Objective: to analyze physicochemical, microbiological and dirt parameters in marketed honeys, consumed by the elderly cared for at Integrated Health Center in Teresina, Piauí, Brazil. Method: the following analyses were performed: color, water activity, humidity, ash, pH, acidity, reducing sugars, total sugars, apparent sucrose and insoluble solids. Contamination indicator bacteria, mesophilic microorganisms, filamentous fungi and yeasts, as well as dirt and foreign matter, performed in the period from April to June 2016. Results: analyses of ash, pH, acidity and insoluble solids were outside current standards. Microbiological analyses did not present significant contamination. Also, analyses of dirt showed insect fragments, foreign matter in almost all the samples. Conclusion: parameters of ash, pH, acidity and insoluble solids, as well as dirt and foreign matter, indicated that the samples were not in accordance with current legislation. 

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