The Experts below are selected from a list of 204 Experts worldwide ranked by ideXlab platform
Joseph Moran - One of the best experts on this subject based on the ideXlab platform.
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A Supramolecular Model for the Co‐Catalytic Role of Nitro Compounds in Brønsted Acid Catalyzed Reactions
Chemistry - A European Journal, 2020Co-Authors: Joel Jose Montalvo Acosta, Marian Dryzhakov, Edward Richmond, Marco Cecchini, Joseph MoranAbstract:Nitro Compounds are known to change reaction rates and kinetic concentration dependence of Brønsted-acid-catalyzed reactions. Yet, no mechanistic model exists to account for these observations. Herein we present an atomistic model for the catalytically active form for an alcohol dehydroazidation reaction, generated by DFT calculations. which consists of an H-bonded aggregate of two molecules of Brønsted acid and two molecules of Nitro Compound. The computed O-H stretching frequencies for the aggregate indicate they are stronger acids than the individual acid molecules and serve as predictors for experimental reaction rates. Applying the model to a chemically diverse set of potential promoters, we predicted and verified experimentally that sulfate esters induce a similar co-catalytic effect. The important implication is that Brønstedacid catalysis must be viewed from a supramolecular perspective that accounts for not only the pKa of the acid and the bulk properties of a solvent, but also the weak interactions between all molecules in solution.
Nurettin Sahiner - One of the best experts on this subject based on the ideXlab platform.
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the resourcefulness of p 4 vp cryogels as template for in situ nanoparticle preparation of various metals and their use in h2 production Nitro Compound reduction and dye degradation
Applied Catalysis B-environmental, 2015Co-Authors: Nurettin Sahiner, Sema Yildiz, Hamad A AllohedanAbstract:Abstract Poly(4-vinylpyridine) (p(4-VP)) cryogels were synthesized under cryogenic conditions (T = −18 °C) and were converted to positively charged forms by modifying with different alkyl dihalides of variable chain lengths such as 1,2-dibromoethane (1,2 BE), 1,4-dibromobutane (1,4 BB), 1,6-dibromohexane (1,6 BH), and 1,8-dibromooctane (1,8 BO). The chemical structure of synthesized supermacroporous 1,4 BB-p(4-VP) cryogels were confirmed by FT-IR spectroscopy. The 1,4 BB modified-poly(4-vinylpyridine) (1,4 BB-p(4-VP)) cryogels were used as template for in situ metal nanoparticle preparation as 1,4 BB-p(4-VP)-M (M: Co, Ni, Cu, and Fe) using chloride salts of Co, Ni, Cu, and Fe in ethanol. These metal-nanoparticle macroporous cryogel composites were employed in H2 generation from hydrolysis of sodium borohydride (NaBH4). Metal nanoparticles embedded 1,4 BB-p(4-VP)-M were visualized by TEM, and thermal behavior of 1,4 BB-p(4-VP) cryogels were done by thermogravimetric analyzer (TGA). The metal content of 1,4 BB-p(4-VP)-M was estimated via atomic absorption spectroscopy (AAS). Multiple metal salt loading and reduction cycles were performed for 1,4 BB-p(4-VP) cryogels to increase the amount of contained Co. The activation energies, enthalpy, and entropy for NaBH4 hydrolysis catalyzed by 1,4 BB-p(4-VP)-Co cryogel composites were determined as 47.6 kJ (mol)−1, 46.2 kJ (mol K)−1, and −146.9 J (mol K)−1, respectively. The cryogel network embedded with Co, Ni, Cu, and Fe nanoparticles was also used as a catalyst in the reduction of 4-Nitrophenol (4-NP) in an aqueous solution in excess amount of NaBH4. Furthermore, the Cu metal nanoparticle-containing 1,4 BB-p(4-VP) cryogel was utilized in the degradation of methylene blue (MB).
Joel Jose Montalvo Acosta - One of the best experts on this subject based on the ideXlab platform.
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A Supramolecular Model for the Co‐Catalytic Role of Nitro Compounds in Brønsted Acid Catalyzed Reactions
Chemistry - A European Journal, 2020Co-Authors: Joel Jose Montalvo Acosta, Marian Dryzhakov, Edward Richmond, Marco Cecchini, Joseph MoranAbstract:Nitro Compounds are known to change reaction rates and kinetic concentration dependence of Brønsted-acid-catalyzed reactions. Yet, no mechanistic model exists to account for these observations. Herein we present an atomistic model for the catalytically active form for an alcohol dehydroazidation reaction, generated by DFT calculations. which consists of an H-bonded aggregate of two molecules of Brønsted acid and two molecules of Nitro Compound. The computed O-H stretching frequencies for the aggregate indicate they are stronger acids than the individual acid molecules and serve as predictors for experimental reaction rates. Applying the model to a chemically diverse set of potential promoters, we predicted and verified experimentally that sulfate esters induce a similar co-catalytic effect. The important implication is that Brønstedacid catalysis must be viewed from a supramolecular perspective that accounts for not only the pKa of the acid and the bulk properties of a solvent, but also the weak interactions between all molecules in solution.
Hamad A Allohedan - One of the best experts on this subject based on the ideXlab platform.
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the resourcefulness of p 4 vp cryogels as template for in situ nanoparticle preparation of various metals and their use in h2 production Nitro Compound reduction and dye degradation
Applied Catalysis B-environmental, 2015Co-Authors: Nurettin Sahiner, Sema Yildiz, Hamad A AllohedanAbstract:Abstract Poly(4-vinylpyridine) (p(4-VP)) cryogels were synthesized under cryogenic conditions (T = −18 °C) and were converted to positively charged forms by modifying with different alkyl dihalides of variable chain lengths such as 1,2-dibromoethane (1,2 BE), 1,4-dibromobutane (1,4 BB), 1,6-dibromohexane (1,6 BH), and 1,8-dibromooctane (1,8 BO). The chemical structure of synthesized supermacroporous 1,4 BB-p(4-VP) cryogels were confirmed by FT-IR spectroscopy. The 1,4 BB modified-poly(4-vinylpyridine) (1,4 BB-p(4-VP)) cryogels were used as template for in situ metal nanoparticle preparation as 1,4 BB-p(4-VP)-M (M: Co, Ni, Cu, and Fe) using chloride salts of Co, Ni, Cu, and Fe in ethanol. These metal-nanoparticle macroporous cryogel composites were employed in H2 generation from hydrolysis of sodium borohydride (NaBH4). Metal nanoparticles embedded 1,4 BB-p(4-VP)-M were visualized by TEM, and thermal behavior of 1,4 BB-p(4-VP) cryogels were done by thermogravimetric analyzer (TGA). The metal content of 1,4 BB-p(4-VP)-M was estimated via atomic absorption spectroscopy (AAS). Multiple metal salt loading and reduction cycles were performed for 1,4 BB-p(4-VP) cryogels to increase the amount of contained Co. The activation energies, enthalpy, and entropy for NaBH4 hydrolysis catalyzed by 1,4 BB-p(4-VP)-Co cryogel composites were determined as 47.6 kJ (mol)−1, 46.2 kJ (mol K)−1, and −146.9 J (mol K)−1, respectively. The cryogel network embedded with Co, Ni, Cu, and Fe nanoparticles was also used as a catalyst in the reduction of 4-Nitrophenol (4-NP) in an aqueous solution in excess amount of NaBH4. Furthermore, the Cu metal nanoparticle-containing 1,4 BB-p(4-VP) cryogel was utilized in the degradation of methylene blue (MB).
Richmond Lee - One of the best experts on this subject based on the ideXlab platform.
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a ruthenium bisoxazoline complex as a photoredox catalyst for Nitro Compound reduction under visible light
Dalton Transactions, 2019Co-Authors: Weiguo Jia, Mingxia Cheng, Lili Gao, Siu Min Tan, Chao Wang, Xiaogang Liu, Richmond LeeAbstract:An unreported ruthenium(ii) complex containing bisoxazoline ligands has been synthesized and characterized. To test the catalytic ability of the ruthenium complex, the synthesis of anilines from Nitro Compounds in the presence of a mild reducing agent sodium borohydride and visible light has been developed. Mechanistic studies involving the experiment and DFT calculations suggest that the reaction could involve a radical pathway with the assistance of a photoredox catalyst.