The Experts below are selected from a list of 291 Experts worldwide ranked by ideXlab platform
Yunfei Li - One of the best experts on this subject based on the ideXlab platform.
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energy estimation and modeling solid thermal explosion containment on reactor for three organic peroxides by calorimetric technique
Journal of Thermal Analysis and Calorimetry, 2017Co-Authors: Yangfan Cheng, Bin Zhang, Yunfei LiAbstract:In this paper, we describe thermokinetic properties and decomposition characteristics of benzoyl peroxide, dicumyl peroxide, and lauroyl peroxide, which are widely used in the polymerization process as energy boosters. In the past, many accidents occurred that involved overpressure and runaway excursion of the process and thermal explosion. One reason for accidents is because of the Peroxy Group (–O–O–) of organic peroxides (OPs) due to its thermal instability and high sensitivity when exposing to heat. Apparent activation energy and pre-exponential factor were obtained during decomposition via non-isothermal well-recognized kinetic equation, fitting curve tests, and approximate solution to design safer reaction conditions when OPs are used as fuel. Moreover, the storage conditions were investigated for the simulation of thermal explosion in a 24-kg cubic box package and a 400-kg barrel reactor for commercial application. Experimental results established the novel features of solid explosion hazard of OPs.
Tohru Sakakibara - One of the best experts on this subject based on the ideXlab platform.
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First preparation of pyranosid nitroolefin having a Peroxy Group and its reaction with some nucleophiles
Tetrahedron Letters, 1993Co-Authors: Akinori Seta, Kiyohisa Tokuda, Tohru SakakibaraAbstract:Abstract Treatment of nitroalkene 1 with t-butyl hydroperoxide and m-chloroperbenzoic acid gave the S n 2′ product and 2,3-anhydro derivative, respectively, in high yields. The former product is proved to be useful intermediate for introduction of nucleophiles at C-4.
Robert I.g. Thompson - One of the best experts on this subject based on the ideXlab platform.
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A study of the mechanism of the oxidative thermal degradation of poly(ethylene oxide) and poly(propylene oxide) using 1H- and 13C-NMR
European Polymer Journal, 1996Co-Authors: Li Yang, Frank Heatley, Trevor Graham Blease, Robert I.g. ThompsonAbstract:Abstract The oxidative thermal degradation of poly(ethylene oxide) (PEO) and poly(propylene oxide) (PPO) at 150 °C in air was studied. The weight loss was determined, and the structure of the residual polymer investigated using NMR. In PEO, the only significant structural changes were the formation of formate ester and hydroxy end-Groups, the former predominating. In PPO, significant amounts of primary hydroxy end-Groups of the structure OCH(CH3)CH2OH and secondary hydroxy end-Groups of the structure CH2CH(CH3)OH were formed, together with their formate and acetate esters. These structural changes have been interpreted in terms of the decomposition of a Peroxy species initially formed by substitution of a backbone hydrogen by a Peroxy Group.
Joseph W. Bozzelli - One of the best experts on this subject based on the ideXlab platform.
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Structures, Rotational Barriers, and Thermochemical Properties of β-Chlorinated Ethyl Hydroperoxides
The Journal of Physical Chemistry A, 2003Co-Authors: Hongyan Sun, Joseph W. BozzelliAbstract:Structures, internal rotational barriers, and thermochemical properties of 2-chloroethyl hydroperoxide, 2,2-dichloroethyl hydroperoxide, and 2,2,2-trichloroethyl hydroperoxide are computed by ab initio and density functional calculations. Molecular structures and vibrational frequencies are determined at the B3LYP/6-31G(d,p) density functional level, with single-point calculations for the energy at the B3LYP/6-311+G(3df,-2p), QCISD(T)/6-31G(d,p), and CBSQ//B3LYP/6-31G(d,p) levels. The S° 2 9 8 and C p (T) values (0 ≤ T/K ≤ 5000) from vibrational, translational, and external rotational contributions are calculated using statistical mechanics based on the vibrational frequencies and structures obtained from the density functional study. Potential barriers for the internal rotations are calculated at the B3LYP/6-31G(d,p) level, and all minima and maxima on the torsional potentials are fully optimized. The hindered rotational contributions to S° 2 9 8 and Cp(T) are calculated by using direct integration over energy levels of the internal rotational potentials. The enthalpies of formation are calculated using isodesmic reactions, and the recommended ΔH f ° 2 9 8 values for CH 2 ClCH 2 OOH, CHCl 2 CH 2 OOH, and CCl 3 CH 2 OOH are -45.47 ′ 1.20, -48.92 ′ 1.50, and -50.21 ′ 1.36 kcal/mol, respectively. Interaction terms for a Peroxy Group with chlorine(s) on a β carbon are developed for the Group additivity approach. Bond energies calculated from the enthalpies of β-chlorinated ethyl hydroperoxides and their corresponding radicals show good agreement with those from our previous studies.
Pedro Domingues - One of the best experts on this subject based on the ideXlab platform.
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Reactivity of Tyr-Leu and Leu-Tyr dipeptides: identification of oxidation products by liquid chromatography-tandem mass spectrometry.
Journal of mass spectrometry : JMS, 2009Co-Authors: Conceição Fonseca, M. Rosário M. Domingues, Cláudia Simões, Francisco Amado, Pedro DominguesAbstract:The exposure of peptides and proteins to reactive hydroxyl radicals results in covalent modifications of amino acid side-chains and protein backbone. In this study we have investigated the oxidation the isomeric peptides tyrosine-leucine (YL) and leucine-tyrosine (LY), by the hydroxyl radical formed under Fenton reaction (Fe(2+)/H(2)O(2)). Through mass spectrometry (MS), high-performance liquid chromatography (HPLC-MS) and electrospray tandem mass spectrometry (HPLC-MS(n)) measurements, we have identified and characterized the oxidation products of these two dipeptides. This approach allowed observing and identifying a wide variety of oxidation products, including isomeric forms of the oxidized dipeptides. We detected oxidation products with 1, 2, 3 and 4 oxygen atoms for both peptides; however, oxidation products with 5 oxygen atoms were only present in LY. LY dipeptide oxidation leads to more isomers with 1 and 2 oxygen atoms than YL (3 vs 5 and 4 vs 5, respectively). Formation of the Peroxy Group occurred preferentially in the C-terminal residue. We have also detected oxidation products with double bonds or keto Groups, dimers (YL-YL and LY-LY) and other products as a result of cross-linking. Both amino acids in the dipeptides were oxidized although the peptides showed different oxidation products. Also, amino acid residues have shown different oxidation products depending on the relative position on the dipeptide. Results suggest that amino acids in the C-terminal position are more prone to oxidation.