Molecular simulations of poly(2,5-benzimidazole): Effect of water concentration, phosphoric acid doping, and temperature on hydrogen bonding and vehicular diffusion

2012 ◽  
Vol 53 (3) ◽  
pp. 597-608 ◽  
Author(s):  
Shuo Li ◽  
J.R. Fried ◽  
John Colebrook
Keyword(s):  
Hydrogen Bonding ◽  
Phosphoric Acid ◽  
Molecular Simulations ◽  
Water Concentration ◽  
Effect Of Water

scholarly journals Organocatalytic enantioselective dearomatization of thiophenes by 1,10-conjugate addition of indole imine methides

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Xingguang Li ◽  
Meng Duan ◽  
Peiyuan Yu ◽  
K. N. Houk ◽  
Jianwei Sun
Keyword(s):  
Hydrogen Bonding ◽  
Phosphoric Acid ◽  
Nucleophilic Addition ◽  
Acid Catalysis ◽  
Conjugate Addition ◽  
Mild Conditions ◽  
Rapid Construction ◽  
Chiral Phosphoric Acid ◽  
Cyclic Molecules ◽  
Selectivity Control

AbstractCatalytic asymmetric dearomatization (CADA) is a powerful tool for the rapid construction of diverse chiral cyclic molecules from cheap and easily available arenes. This work reports an organocatalytic enantioselective dearomatization of substituted thiophenes in the context of a rare remote asymmetric 1,10-conjugate addition. By suitable stabilization of the thiophenyl carbocation with an indole motif in the form of indole imine methide, excellent remote chemo-, regio-, and stereocontrol in the nucleophilic addition can be achieved with chiral phosphoric acid catalysis under mild conditions. This protocol can be successfully extended to the asymmetric dearomatization of other heteroarenes including selenophenes and furans. Control experiments and DFT calculations demonstrate a possible pathway in which hydrogen bonding plays an important role in selectivity control.

scholarly journals Insight into Cellulose Dissolution with the Tetrabutylphosphonium Chloride–Water Mixture using Molecular Dynamics Simulations

Polymers ◽  
2020 ◽  
Vol 12 (3) ◽  
pp. 627 ◽  
Author(s):  
Brad Crawford ◽  
Ahmed E. Ismail
Keyword(s):  
Molecular Dynamics ◽  
Hydrogen Bonding ◽  
Molecular Dynamics Simulations ◽  
Water Solution ◽  
Water Concentration ◽  
High Water ◽  
Water Mixture ◽  
Cellulose Dissolution ◽  
Working Together ◽  
Dynamics Simulations

All-atom molecular dynamics simulations are utilized to determine the properties and mechanisms of cellulose dissolution using the ionic liquid tetrabutylphosphonium chloride (TBPCl)–water mixture, from 63.1 to 100 mol % water. The hydrogen bonding between small and large cellulose bundles with 18 and 88 strands, respectively, is compared for all concentrations. The Cl, TBP, and water enable cellulose dissolution by working together to form a cooperative mechanism capable of separating the cellulose strands from the bundle. The chloride anions initiate the cellulose breakup, and water assists in delaying the cellulose strand reformation; the TBP cation then more permanently separates the cellulose strands from the bundle. The chloride anion provides a net negative pairwise energy, offsetting the net positive pairwise energy of the peeling cellulose strand. The TBP–peeling cellulose strand has a uniquely favorable and potentially net negative pairwise energy contribution in the TBPCl–water solution, which may partially explain why it is capable of dissolving cellulose at moderate temperatures and high water concentrations. The cellulose dissolution declines rapidly with increasing water concentration as hydrogen bond lifetimes of the chloride–cellulose hydroxyl hydrogens fall below the cellulose’s largest intra-strand hydrogen bonding lifetime.

Effect of water concentration on photoreduction of anthraquinone-2-sulfonate by 2-propanol in aqueous acetonitrile solution

1987 ◽  
Vol 91 (26) ◽  
pp. 6547-6551 ◽  
Author(s):  
Akihiro. Wakisaka ◽  
Thomas W. Ebbesen ◽  
Hirochika. Sakuragi ◽  
Katsumi. Tokumaru
Keyword(s):  
Water Concentration ◽  
Acetonitrile Solution ◽  
Aqueous Acetonitrile ◽  
Effect Of Water
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