Thermal degradation of EDTA chelates in aqueous solution

1982 ◽  
Vol 60 (10) ◽  
pp. 1207-1213 ◽  
Author(s):  
Ramunas J. Motekaitis ◽  
X. B. Cox III ◽  
Patrick Taylor ◽  
Arthur E. Martell ◽  
Brad Miles ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Thermal Degradation ◽  
Elevated Temperatures ◽  
Degradation Products ◽  
Iminodiacetic Acid ◽  
Reaction Products ◽  
Degradation Rates ◽  
Lower Temperature Range ◽  
Higher Temperature ◽  
Lower Temperature

The thermal degradation of Ca(II), Mg(II), Zn(II), Fe(II), and Ni(II) chelates of EDTA was investigated in alkaline aqueous solution at elevated temperatures (230–310 °C). The kinetics of decomposition were followed by nmr, titrimetry, and spectrophotometry. Reaction products were identified through nmr and by gas chromatography. The relative order of degradation rates, as measured by the loss of EDTA, was found to be Mg(II) > Ca(II) > Zn(II) > Fe(II) > Ni(II). The main degradation products formed in the lower temperature range (~250 °C) are iminodiacetic acid, hydroxyethyliminodiacetic acid, and ethylene glycol. Higher temperature products are primarily dimethylamine and carbon dioxide. The rates of degradation of Ca(II), Mg(II), and Zn(II) EDTA chelates are considerably enhanced when either phosphate is present or a glass-lined autoclave is employed.

scholarly journals “Thermal Peroxidation” of Dietary Pentapeptides Yields N-Terminal 1,2-Dicarbonyls

2021 ◽  
Vol 8 ◽  
Author(s):  
Maria Bikaki ◽  
Nikolai Kuhnert
Keyword(s):  
Lipid Peroxidation ◽  
Reaction Mechanism ◽  
Thermal Degradation ◽  
Primary Amine ◽  
Elevated Temperatures ◽  
Degradation Products ◽  
Degradation Mechanism ◽  
Reaction Products ◽  
Unsaturated Lipids

In this contribution we investigate the thermal degradation of dietary-relevant pentapeptides. Most unsaturated lipids degrade by the well-known peroxidation mechanism. Here we show a degradation mechanism of peptides analogous to lipid peroxidation, forming a series of novel degradation products with possible toxicological relevance. At elevated temperatures above 180°C, pentapeptides with an N-terminal phenylalanine moiety react via a debenzylation to form 1,2-dicabonyl compounds, replacing the N-terminal primary amine. We propose a radical-based reaction mechanism that leads via a common peroxoaminal intermediate to two distinct types of reaction products with a terminal α-1,2 diamide or an α-amide-aldehyde functionality.

The iron(III)-catalyzed oxidation of EDTA in aqueous solution

1980 ◽  
Vol 58 (19) ◽  
pp. 1999-2005 ◽  
Author(s):  
Ramunas J. Motekaitis ◽  
Arthur E. Martell ◽  
David Hayes ◽  
Wayne W. Frenier
Keyword(s):  
Aqueous Solution ◽  
Elevated Temperatures ◽  
Iminodiacetic Acid ◽  
Nitrilotriacetic Acid ◽  
Similar Reaction ◽  
Reactive Intermediate ◽  
Reaction Products ◽  
Reaction Proceeds ◽  
Catalyzed Oxidation ◽  
By Products

At temperatures above 100 °C iron(III) oxidizes coordinated EDTA to ethylenediaminetriacetic acid in aqueous solution in the absence of molecular oxygen. The reaction proceeds with an activation energy of 28.6 kcal/mol, and its rate is directly proportional to the concentration of Fe(III) and inversely proportional to pH. At 125 °C, the halflife of Fe(III) in the presence of excess EDTA is about 3 h at pH 9.3, but increases to >70 h at pH 5.4. The reaction is stoichiometric and no other reaction products or by-products were detected by nmr, gc, and gc – mass spectroscopy. In the presence of oxygen iron catalyzes quantitative oxidation of ethylenediamine-N,N,N′,N′-tetraacetic acid (EDTA) to ethylenediaminetriacetic acid. The copper(II)–EDTA chelate undergoes a similar reaction but higher temperatures [Formula: see text] are required. Iron(III) also oxidizes nitrilotriacetic acid (NTA) to iminodiacetic acid (IDA) and glycine. The hydrolyzed species Fe(OH)EDTA is shown to be the reactive intermediate, and the well-known (Fe–EDTA)2O4− μ-oxo dimer is shown not to exist at elevated temperatures (above 100 °C). Probable mechanisms are proposed for these reactions and comparisons are made with earlier work.

Theoretical Investigation of the CO2 Capture Properties of γ-LiAlO2 and α-Li5AlO4

2019 ◽  
Vol 11 ◽  
Author(s):  
Yuhua Duan
Keyword(s):  
Co2 Capture ◽  
Wide Band ◽  
Band Gaps ◽  
Lithium Aluminate ◽  
Free Energies ◽  
Solid Sorbents ◽  
Lower Temperature Range ◽  
Higher Temperature ◽  
Valence Bands ◽  
Lower Temperature

: Lithium aluminate has attracted researchers’ interests due to its wide applications. By combining electronic structural and lattice phonon thermodynamic calculations, the CO2 capture properties of γ-LiAlO2 and α-Li5AlO4 are investigated. Both γ-LiAlO2 and α-Li5AlO4 are insulators with wide band gaps of 4.70 and 4.76 eV respectively. Their 1st valence bands just below the Fermi level are mainly formed by p orbitals of Li, O and Al as well as s orbital of Li. By increasing the temperature from 0 K up to 1500 K, their phonon free energies are decreased while their entropies are increased. Targeting on developing post- and pre-combustion CO2 capture technologies, the obtained results indicated that γ-LiAlO2 is thermodynamically favorable to capture CO2 at lower temperature range (500-800 K) while α-Li5AlO4 could capture CO2 at higher temperature (800-1000 K) range in comparison with other solid sorbents, such as pure Li2O, Li4SiO4 and Li2ZrO3.

Scanning UV microspectrophotometry as a tool to study the changes of lignin in hydrothermally modified wood

Holzforschung ◽  
2016 ◽  
Vol 70 (3) ◽  
pp. 215-221 ◽  
Author(s):  
Bruno Andersons ◽  
Guna Noldt ◽  
Gerald Koch ◽  
Ingeborga Andersone ◽  
Anete Meija-Feldmane ◽  
...  
Keyword(s):  
Cell Wall ◽  
Degradation Products ◽  
Middle Lamella ◽  
Temperature Range ◽  
Wood Protection ◽  
Lower Temperature Range ◽  
Lower Temperature ◽  
The One ◽  
S2 Layer ◽  
Uv Microspectrophotometry

Abstract Thermal modification (TM) of wood has occupied a relatively narrow but stable niche as an alternative for chemical wood protection. There are different technological solutions for TM and not all details of their effects on wood tissue have been understood. The one-stage hydrothermal modification (HTM) at elevated vapour pressure essentially changes the wood’s composition and structure. In the present paper, the changes in three hardwood lignins (alder, aspen, and birch) were observed within the cell wall by means of cellular UV microspectrophotometry. The lignin absorbances in the compound middle lamella (CML) of unmodified wood are 1.7- to 2.0-fold higher than those in the fibre S2 layer. The woods were modified in the temperature range from 140 to 180°C, while in the lower temperature range (140°C/1 h), the UV absorbances are little affected. Essential changes occur in the range of 160–180°C and the UV data reflect these by absorbtion changes, while the absorbances at 278 nm rise with factors around 2 more in the S2 layer than in the CML. The absorbance increments are interpreted as polycondensation reactions with furfural and other degradation products of hemicelluloses with the lignin moiety of the cell wall.

scholarly journals Journal of Food Quality Thermal Degradation of Plum Anthocyanins: Comparison of Kinetics from Simple to Natural Systems

2018 ◽  
Vol 2018 ◽  
pp. 1-10 ◽  
Author(s):  
Mihaela Turturică ◽  
Nicoleta Stănciuc ◽  
Claudia Mureșan ◽  
Gabriela Râpeanu ◽  
Constantin Croitoru
Keyword(s):  
Antioxidant Activity ◽  
Citric Acid ◽  
Thermal Degradation ◽  
Fluorescence Spectra ◽  
Degradation Rate ◽  
Natural Systems ◽  
Degradation Rate Constant ◽  
Higher Temperature ◽  
Lower Temperature ◽  
The Stability

The stability of anthocyanin was assessed over a temperature range of 50–120°C in different simulated plum juices in order to compare the thermal behavior in the presence of certain compounds. The results were correlated with the antioxidant activity and intrinsic fluorescence spectra. The results suggested significant changes, especially at higher temperature; hence, increase in the fluorescence intensity and some bathochromic and hypsochromic shifts were observed. Anthocyanins in natural matrices presented the highest rate for degradation, followed by the anthocyanins in juices with sugars. Values of the activation energies were 42.40 ± 6.87 kJ/mol for the degradation in water, 40.70 ± 4.25 kJ/mol for the juices with citric acid, 23.03 ± 3.53 kJ/mol for the juices containing sugars, 35.99 ± 3.60 kJ/mol for simulated juices with mixture, and 14.19 ± 2.39 kJ/mol for natural juices. A protective effect of sugars was evidenced, whereas in natural matrices, the degradation rate constant showed lower temperature dependence.

Hydrolysis and ammonolysis of EDTA in aqueous solution

1979 ◽  
Vol 57 (9) ◽  
pp. 1018-1024 ◽  
Author(s):  
Ramunas J. Motekaitis ◽  
David Hayes ◽  
Arthur E. Martell ◽  
Wayne W. Frenier
Keyword(s):  
Aqueous Solution ◽  
Iminodiacetic Acid ◽  
Order Rate Constant ◽  
Spectroscopic Techniques ◽  
Reaction Products ◽  
First Order ◽  
Molar Ratios ◽  
Ph Values ◽  
Rate Of Hydrolysis ◽  
Protonated Nitrogen Atom

The hydrolysis and ammonolysis of EDTA were studied in aqueous solution over a range of temperatures and at various pH values with the aid of nmr, gc, and gc – mass spectroscopic techniques. At high pH in the presence of ammonia, both ammonolysis and hydrolysis occur with the production of N-(2-aminoethyl)iminodiacetic acid (UEDDA), N-(2-hydroxyethyl)-iminodiacetic acid (HEIDA), and iminodiacetic acid (IDA) in molar ratios such that [IDA] = [UEDDA] + [HEIDA]. The first-order rate constant for the disappearance of EDTA at 175 °C in dilute aqueous ammonia is 8.6 × 10−5 s−1 whereas in the absence of ammonia its hydrolysis constant is 4.2 × 10−5 s−1. The value of ΔH0 for this reaction is approximately 35 kcal/mol. When methylamine replaces ammonia, the UEDDA is replaced by N-(2-methylaminoethyl)iminodiacetic acid. The rate of hydrolysis is increased by the presence of a tertiary amine but the latter does not become incorporated into the reaction products. A reaction mechanism is proposed involving bimolecular SN2 attack by base on a carbon atom of the ethylene bridge adjacent to a protonated nitrogen atom of EDTA with concomitant displacement of iminodiacetic acid.

High-Temperature Electromechanical Properties of CTGS

2014 ◽  
Vol 1655 ◽  
Author(s):  
Michal Schulz ◽  
Holger Fritze ◽  
Ward L. Johnson
Keyword(s):  
Resonance Frequency ◽  
Elevated Temperatures ◽  
Bulk Acoustic Wave ◽  
Linear Temperature Dependence ◽  
Temperature Dependent ◽  
Electromechanical Properties ◽  
Linear Temperature ◽  
Sensing Applications ◽  
Lower Temperature Range ◽  
Lower Temperature

ABSTRACTCTGS (Ca3TaGa3Si2O14) is a commercially available, Czochralski-grown piezoelectric material from the langasite family that has an ordered crystal structure. It can be excited piezoelectrically up to at least 1285 °C, which is very close to the melting temperature of 1350 °C. In order to determine the loss at elevated temperatures, two different resonance techniques are used. A contactless transduction method is employed up to about 600 °C, whereas transduction involving standard keyhole-shaped film electrodes is employed up to 1285 °C. Comparison of the temperature-dependent inverse Q factor shows that contactless measurements are best suited for the lower temperature range, where sample clamping and losses caused by the electrodes contribute significantly to the total loss. However, at higher temperatures, measurement of the electrical impedance of samples with film electrodes in the vicinity of the resonance frequency proves to be suitable. Even at 1100 °C, 5 MHz CTGS resonators are found to have a Q factor of about 1200, which is great enough to enable numerous bulk-acoustic-wave applications. Further, a nearly linear temperature dependence of the resonance frequency with a temperature coefficient of 210 Hz/K makes Y-cut CTGS well suited for temperature-sensing applications.

Asymmetric Reactions in Water Catalyzed by L-Proline Tethered on Thermoresponsive Ionic Copolymers

2020 ◽  
Vol 17 (9) ◽  
pp. 717-725
Author(s):  
Noriyuki Suzuki ◽  
Daisuke Mizuno ◽  
Armando M. Guidote ◽  
Shun Koyama ◽  
Yoshiro Masuyama ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Block Copolymers ◽  
Solution Temperature ◽  
Critical Solution Temperature ◽  
Copolymer Solution ◽  
Lcst Behavior ◽  
Higher Temperature ◽  
Lower Temperature ◽  
Thermal Stimuli ◽  
Clear Solution

L-Proline was covalently tethered on thermoresponsive ionic block copolymers that formed micelles in aqueous solutions. The block copolymers consisted of a poly(N-isopropylacrylamide) (PNIPAAm) segment and an anionic or cationic polymer segment. These copolymers exhibited lower critical solution temperature (LCST) behavior at ca. 35-40°C, and achieved thermal stimuli-induced formation and dissociation of micelles. The copolymer generated micelles in aqueous solution at a higher temperature, where a catalytic aldol reaction proceeded with high diastereo- and enantioselectivities. The micelles dissociated at lower temperature to form a clear solution such that the products could be efficiently extracted from the aqueous reaction mixture. Extraction of the aldol product with an organic solvent from the aqueous solution of the anionic copolymer was more efficient than from the nonionic copolymer solution.

Thermal Degradation of Ionic Liquids at Elevated Temperatures

2004 ◽  
Vol 57 (2) ◽  
pp. 145 ◽  
Author(s):  
Krisztian J. Baranyai ◽  
Glen B. Deacon ◽  
Douglas R. MacFarlane ◽  
Jennifer M. Pringle ◽  
Janet L. Scott
Keyword(s):  
Thermal Stability ◽  
Ionic Liquids ◽  
Thermal Degradation ◽  
Elevated Temperatures ◽  
Degradation Products ◽  
Operating Temperature ◽  
Imidazolium Cation

Ionic liquids based on the imidazolium cation are found to degrade, yielding volatile degradation products, at temperatures significantly lower than previously reported and thus a parameter Tz/x (the maximum operating temperature) is developed to provide a more appropriate estimate of thermal stability.

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