The Experts below are selected from a list of 252 Experts worldwide ranked by ideXlab platform
George A. Olah - One of the best experts on this subject based on the ideXlab platform.
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poly 4 vinylpyridine nitrating mixture complex pvp nm solid nitrating mixture equivalent for safe and efficient Aromatic Nitration
Green Chemistry, 2015Co-Authors: G Surya K Prakash, Laxman Gurung, Kevin E Glinton, Kavita Belligund, Thomas Mathew, George A. OlahAbstract:Friedel–Crafts type Aromatic Nitration has served as an indispensable reaction within both industrial and academic applications. However, growing concern over the use of copious amounts of strong acids has prompted the search for more environmentally friendly alternatives. Polymer-bound Bronsted acids, on the other hand, have been shown useful as convenient alternatives to liquid acids. Nitric acid and sulfuric acids have, therefore, been combined, both individually and as a mixture, with poly(4-vinylpyridine). The new solid acid systems have been used to nitrate both activated and deactivated arenes under mild conditions and proved to be effective nitrating agent.
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Unified mechanistic concept of electrophilic Aromatic Nitration: convergence of computational results and experimental data.
Journal of the American Chemical Society, 2003Co-Authors: Pierre M. Esteves, G. K. Surya Prakash, José Walkimar De M. Carneiro, Sheila Pressentin Cardoso, André G. H. Barbosa, Kenneth K. Laali, Golam Rasul, George A. OlahAbstract:The mechanism of electrophilic Aromatic Nitration was revisited. Based on the available experimental data and new high-level quantum chemical calculations, a modification of the previous reaction mechanism is proposed involving three separate intermediates on the potential energy diagram of the reaction. The first, originally considered an unoriented π-complex or electron donor acceptor complex (EDA), involves high electrostatic and charge-transfer interactions between the nitronium ion and the π-Aromatics. It explains the observed low substrate selectivity in Nitration with nitronium salts while maintaining high positional selectivity, as well as observed oxygen transfer reactions in the gas phase. The subsequent second intermediate originally considered an oriented “π-complex” is now best represented by an intimate radical cation−molecule pair, C6H6+•/NO2, that is, a SET complex, indicative of single-electron transfer from the Aromatic π-system to NO2+. Subsequently, it collapses to afford the final σ-c...
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Aromatic Nitration with Nitric Acid/Trifluoromethanesulfonic Anhydride
Synthesis, 2002Co-Authors: George A. Olah, Prakash Reddy, G. K. Surya PrakashAbstract:Nitric acid/trifluoromethanesulfonic (triflic) anhydride was shown to be a highly effective electrophilic nitrating agent. A series of Aromatics were nitrated under mild conditions in high yields. Similar results were also obtained when using nitric acid/trifluoromethane-sulfonic acid/phosphorus pentoxide as nitrating agent in nitroethane or nitromethane solution. The 15 N NMR spectrum of 15 N enriched nitric acid in triflic anhydride was studied and compared with that of other nitrating reagents. The data indicate the predominantly covalent nature of trifluoromethanesulfonyl nitrate formed in the systems
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Aromatic Nitration with potassium nitrate or nitric acid and boron trifluoride monohydrate
Synthesis, 1992Co-Authors: George A. Olah, Qi Wang, Imre BucsiAbstract:Potassium nitrate/boron trifluoride monohydrate and nitric acid/boron trifluoride monohydrate have been found to be efficient reagents for the Nitration of Aromatic compounds. Benzene and a series of substituted benzenes were nitrated with excellent yields
Linjie Liang - One of the best experts on this subject based on the ideXlab platform.
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An Efficient and Eco-friendly MoO3–SiO2 Solid Acid Catalyst for Electrophilic Aromatic Nitration with N2O5
Catalysis Letters, 2011Co-Authors: Linjie LiangAbstract:Electrophilic Aromatic Nitration using N2O5 as a green nitrating agent catalyzed by MoO3–SiO2 under mild conditions has been described. A series of MoO3–SiO2 catalysts with varying MoO3 loadings (5–20 mol%) were prepared by sol–gel technique and characterized using FTIR, XRD, SEM, BET and NH3–TPD to study its surface properties. MoO3–SiO2 shows good catalytic activity and reusability for the Nitration of alkyl and halogen Aromatics giving high conversions, but less efficiency for the deactivated Aromatics. Reactions conducted under non-acidic conditions using N2O5 makes the process safe and environmentally friendly.
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an efficient and eco friendly moo3 sio2 solid acid catalyst for electrophilic Aromatic Nitration with n2o5
Catalysis Letters, 2011Co-Authors: Linjie LiangAbstract:Electrophilic Aromatic Nitration using N2O5 as a green nitrating agent catalyzed by MoO3–SiO2 under mild conditions has been described. A series of MoO3–SiO2 catalysts with varying MoO3 loadings (5–20 mol%) were prepared by sol–gel technique and characterized using FTIR, XRD, SEM, BET and NH3–TPD to study its surface properties. MoO3–SiO2 shows good catalytic activity and reusability for the Nitration of alkyl and halogen Aromatics giving high conversions, but less efficiency for the deactivated Aromatics. Reactions conducted under non-acidic conditions using N2O5 makes the process safe and environmentally friendly.
Claudio Tortato - One of the best experts on this subject based on the ideXlab platform.
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sulfuric acid on silica gel an inexpensive catalyst for Aromatic Nitration
Tetrahedron Letters, 1996Co-Authors: J Riego, Zeno Sedin, Josem Zaldivar, N C Marziano, Claudio TortatoAbstract:Abstract Solid acidic catalysts made of sulfuric acid supported on silica-gel and their application to the Nitration of Aromatics with nitric acid and isopropyl nitrate are described. Substrates with very different levels of activation were investigated. Methods to overcome the poisoning produced by water and to tune the catalyst activity according to the reactivity of the substrate are outlined.
Kenneth K. Laali - One of the best experts on this subject based on the ideXlab platform.
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ethylammonium nitrate ean tf2o and ean tfaa ionic liquid based systems for Aromatic Nitration
ChemInform, 2012Co-Authors: Gopalakrishnan Aridoss, Kenneth K. LaaliAbstract:The nitrating agents allow formation of a wide range of nitroarenes in high yields under simple and mild conditions.
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ethylammonium nitrate ean tf2o and ean tfaa ionic liquid based systems for Aromatic Nitration
Journal of Organic Chemistry, 2011Co-Authors: Gopalakrishnan Aridoss, Kenneth K. LaaliAbstract:Acting as in situ sources of triflyl nitrate (TfONO2) and trifluoroacetyl nitrate (CF3COONO2), the EAN/Tf2O and EAN/TFAA systems, generated via metathesis in the readily available ethylammonium nitrate (EAN) ionic liquid as solvent, are powerful electrophilic nitrating reagents for a wide variety of Aromatic and heteroAromatic compounds. Comparative Nitration experiments indicate that EAN/Tf2O is superior to EAN/TFAA for Nitration of strongly deactivated systems. Both systems exhibit low substrate selectivity (KT/KB = 5–10) in between values reported for covalent nitrates and preformed nitronium salts.
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Unified mechanistic concept of electrophilic Aromatic Nitration: convergence of computational results and experimental data.
Journal of the American Chemical Society, 2003Co-Authors: Pierre M. Esteves, G. K. Surya Prakash, José Walkimar De M. Carneiro, Sheila Pressentin Cardoso, André G. H. Barbosa, Kenneth K. Laali, Golam Rasul, George A. OlahAbstract:The mechanism of electrophilic Aromatic Nitration was revisited. Based on the available experimental data and new high-level quantum chemical calculations, a modification of the previous reaction mechanism is proposed involving three separate intermediates on the potential energy diagram of the reaction. The first, originally considered an unoriented π-complex or electron donor acceptor complex (EDA), involves high electrostatic and charge-transfer interactions between the nitronium ion and the π-Aromatics. It explains the observed low substrate selectivity in Nitration with nitronium salts while maintaining high positional selectivity, as well as observed oxygen transfer reactions in the gas phase. The subsequent second intermediate originally considered an oriented “π-complex” is now best represented by an intimate radical cation−molecule pair, C6H6+•/NO2, that is, a SET complex, indicative of single-electron transfer from the Aromatic π-system to NO2+. Subsequently, it collapses to afford the final σ-c...
J Riego - One of the best experts on this subject based on the ideXlab platform.
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sulfuric acid on silica gel an inexpensive catalyst for Aromatic Nitration
Tetrahedron Letters, 1996Co-Authors: J Riego, Zeno Sedin, Josem Zaldivar, N C Marziano, Claudio TortatoAbstract:Abstract Solid acidic catalysts made of sulfuric acid supported on silica-gel and their application to the Nitration of Aromatics with nitric acid and isopropyl nitrate are described. Substrates with very different levels of activation were investigated. Methods to overcome the poisoning produced by water and to tune the catalyst activity according to the reactivity of the substrate are outlined.