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51.
Younes Valadbeigi 《Molecular physics》2013,111(6):577-583
Reactions between CH3NHNH2 and OOH radical were studied using computational methods. The activation energies (Ea) and Gibbs free energies of activation (ΔG#) were calculated at the MP2 and B3LYP levels of theory. The calculated activation energies of the hydrogen abstraction reactions were less than 100 kJ/mol and those for the substitution reactions were about 150–250 kJ/mol. The calculated activation energies for the intra-molecular hydrogen transfer reactions in CH3NHNH, CH2NNH2 and CH3NN molecules were 210–250 kJ/mol. Catalytic effect of the water molecule on the intra-molecular hydrogen transfer reactions was studied. It was found that the water molecule decreases the activation energies by about 70–100 kJ/mol. Rate constants of the reactions were calculated using transition state theory in the temperature range of 298–2000 K. Consecutive hydrogen abstraction reactions from CH3NHNH2 led to the formation of CH2NN, which was a very stable molecule. 相似文献
52.
Younes Valadbeigi Vahideh Ilbeigi Maryam S. Mirsharifi 《Journal of mass spectrometry : JMS》2020,55(10)
Atmospheric pressure chemical ionizations (APCIs) of morphine, codeine, and thebaine were studied in a corona discharge ion source using ion mobility spectrometry (IMS) at temperature range of 100°C–200°C. Density functional theory (DFT) at the B3LYP/6‐311++G(d,p) and M062X/6‐311++G(d,p) levels of theory were used to interpret the experimental data. It was found that in the presence of H3O+ as reactant ion (RI), ionization of morphine and codeine proceeds via both the protonation and carbocation formation, whereas thebaine participates only in protonation. Carbocation formation (fragmentation) was diminished with decrease in the temperature. At lower temperatures, proton‐bound dimers of the compounds were also formed. Ammonia was used as a dopant to produce NH4+ as an alternative RI. In the presence of NH4+, proton transfer from ammonium ion to morphine, codeine, and thebaine was the dominant mechanism of ionization. However, small amount of ammonium attachment was also observed. The theoretical calculations showed that nitrogen atom of the molecules is the most favorable proton acceptor site while the oxygen atoms participate in ammonium attachment. Furthermore, formation of the carbocations is because of the water elimination from the protonated forms of morphine and codeine. 相似文献
53.
Dr. Sabry H. H. Younes Dr. Florian Tieves Dr. Dongming Lan Prof. Dr. Yonghua Wang Dr. Philipp Süss Dr. Henrike Brundiek Prof. Dr. Ron Wever Prof. Dr. Frank Hollmann 《ChemSusChem》2020,13(1):97-101
A chemoenzymatic method for the halocyclization of unsaturated alcohols and acids by using the robust V-dependent chloroperoxidase from Curvularia inaequalis (CiVCPO) as catalyst has been developed for the in situ generation of hypohalites. A broad range of halolactones and cyclic haloethers are formed with excellent performance of the biocatalyst. 相似文献
54.
Dr. Sabry H. H. Younes Dr. Florian Tieves Dr. Dongming Lan Prof. Dr. Yonghua Wang Dr. Philipp Süss Dr. Henrike Brundiek Prof. Dr. Ron Wever Prof. Dr. Frank Hollmann 《ChemSusChem》2020,13(1):5-5
Invited for this month's cover is the group of Prof. Dr. Frank Hollmann at Delft University of Technology in the Netherlands. The Front Cover shows the vanadium-dependent haloperoxidase from the marine organism Curcuvaria inaequalis , which efficiently activates halides as hypohalites that can then initiate spontaneous halo-lactonization and halo-etherification reactions. The Communication itself is available at 10.1002/cssc.201902240 . 相似文献
55.
Hamdi Barkaoui Haitham Abid Szymon Zelewski Joanna Urban Michal Baranowski Adnen Mlayah Smail Triki Paulina Plochocka Younes Abid 《Advanced Optical Materials》2019,7(20)
The synthesis and the optical properties of a new organic–inorganic hybrid material (C6H22N4)[Pb2Br8] (abbreviated as TETAPb2Br8) is reported here. Its ladder‐like crystal structure is built up from infinite 1D chains of corner‐sharing [Pb2Br8]4− bi‐octahedra surrounded by tetra‐protonated triethylenetetramine (abbreviated as TETA4+) organic cations. Under UV excitation, this hybrid organic–inorganic compound emits white light due to radiative recombinations of self‐trapped excitons associated with a structural distortion of the PbBr6 octahedra. Thin films of TETAPb2Br8 show a photoluminescence (PL) quantum yield of ≈11% and exhibit a Commission Internationale de l'Eclairage coordinates of (0.32, 0.37). In the low‐temperature range, the PL intensity increases with increasing temperature. This negative thermal quenching of white‐light emission is interpreted in terms of transitions between excitonic states involving an exciton–phonon interaction. The interpretations are supported by the temperature dependence of the resonant Raman scattering and by density functional theory calculations. 相似文献
56.
Dr. Baptiste Joalland Nuwandi M. Ariyasingha Hassan R. Younes Shiraz Nantogma Dr. Oleg G. Salnikov Dr. Nikita V. Chukanov Dr. Kirill V. Kovtunov Prof. Igor V. Koptyug Prof. Juri G. Gelovani Prof. Eduard Y. Chekmenev 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(8):2774-2781
Many MRI contrast agents formed with the parahydrogen-induced polarization (PHIP) technique exhibit biocompatible profiles. In the context of respiratory imaging with inhalable molecular contrast agents, the development of nonflammable contrast agents would nonetheless be highly beneficial for the biomedical translation of this sensitive, high-throughput and affordable hyperpolarization technique. To this end, we assess the hydrogenation kinetics, the polarization levels and the lifetimes of PHIP hyperpolarized products (acids, ethers and esters) at various degrees of fluorine substitution. The results highlight important trends as a function of molecular structure that are instrumental for the design of new, safe contrast agents for in vivo imaging applications of the PHIP technique, with an emphasis on the highly volatile group of ethers used as inhalable anesthetics. 相似文献
57.
Marouane Mohaddab Younes El Goumi Monica Gallo Domenico Montesano Gokhan Zengin Abdelhakim Bouyahya Malika Fakiri 《Molecules (Basel, Switzerland)》2022,27(22)
Medicinal plants are rich sources of bioactive compounds widely used as medicaments, food additives, perfumes, and agrochemicals. These secondary compounds are produced under stress conditions to carry out physiological tasks in plants. Secondary metabolites have a complex chemical structure with pharmacological properties. The widespread use of these metabolites in a lot of industrial sectors has raised the need to increase the production of secondary metabolites. Biotechnological methods of cell culture allow the conservation of plants, as well as the improvement of metabolite biosynthesis and the possibility to modify the synthesis pathways. The objective of this review is to outline the applications of different in vitro culture systems with previously reported relevant examples for the optimal production of plant-derived secondary metabolites. 相似文献
58.
Hossein Adelnia Hossein Riazi Younes Saadat Soleyman Hosseinzadeh 《Colloid and polymer science》2013,291(7):1741-1748
In this work, monodisperse polystyrene (PS) particles were synthesized in ethanol/water medium using sodium salt of styrene sulfonic acid and 2,2′-azobis(isobutyronitrile) as ionic comonomer and nonionic initiator, respectively. The polymerization was carried out at low agitation speed, and no stabilizer (or surfactant) was added to the polymerization medium. This polymerization system (stabilizer-free dispersion polymerization) was initiated as a homogeneous solution of monomer, comonomer, medium, and initiator. With the production of free radicals, polymerization developed into a heterogeneous system. The effect of various polymerization conditions on the size and size distribution of the obtained particles was evaluated. The experimental results showed that with an increase in ethanol content, the size of the particles increased while no significant change was observed in particle size distribution. Furthermore, with increasing ionic comonomer content, the size of the particles decreased and their size distribution became broader. Moreover, it was observed that addition of an electrolyte to the polymerization medium also increased the particles’ size and broadened their size distribution. It is noteworthy to point out that the coagulation occurred in higher amounts of electrolyte. Finally, it is concluded that the polar component of Hansen solubility parameter of the polymerization medium affects the particle size and particle size distribution greatly. 相似文献
59.
Younes Sohrabi;Fatemeh Rahimian;Saeed Yousefinejad;Fereshteh Aliasghari;Esmaeel Soleimani; 《Biomedical chromatography : BMC》2024,38(7):e5883
The application of green microextraction techniques (METs) is constantly being developed in different areas including pharmaceutical, forensic, food and environmental analysis. However, they are less used in biological monitoring of workers in occupational settings. Developing valid extraction methods and analytical techniques for the determination of occupational indicators plays a critical role in the management of workers’ exposure to chemicals in workplaces. Microextraction techniques have become increasingly important because they are inexpensive, robust and environmentally friendly. This study aimed to provide a comprehensive review and interpret the applications of METs and novel sorbents and liquids in biological monitoring. Future perspectives and occupational indicators that METs have not yet been developed for are also discussed. 相似文献
60.
Zhao Yuan Qing Tang Kesavapillai Sreenath J. Tyler Simmons Ali H. Younes De‐en Jiang Lei Zhu 《Photochemistry and photobiology》2015,91(3):586-598
2‐(2′‐Hydroxyphenyl)benzoxazole (HBO) is known for undergoing intramolecular proton transfer in the excited state to result in the emission of its tautomer. A minor long‐wavelength absorption band in the range 370–420 nm has been reported in highly polar solvents such as dimethylsulfoxide (DMSO). However, the nature of this species has not been entirely clarified. In this work, we provide evidence that this long‐wavelength absorption band might have been caused by base or metal salt impurities that are introduced into the spectral sample during solvent transport using glass Pasteur pipettes. The contamination by base or metal salt could be avoided by using borosilicate glass syringes or nonglass pipettes in sample handling. Quantum chemical calculations conclude that solvent‐mediated deprotonation is too energetically costly to occur without the aid of a base of an adequate strength. In the presence of such a base, the deprotonation of HBO and its effect on emission are investigated in dichloromethane and DMSO, the latter of which facilitates deprotonation much more readily than the former. Finally, the absorption and emission spectra of HBO in 13 solvents are reported, from which it is concluded that ESIPT is hindered in polar solvents that are also strong hydrogen bond acceptors. 相似文献