Effects of Salts, Acids, and Phenols on the Hydrogen-Bonding Structure of Water−Ethanol Mixtures

Nose, Akira; Hojo, Masashi; Ueda, Tadaharu

doi:10.1021/jp0308312

Cited by 70 publications

(70 citation statements)

References 32 publications

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“…[41] The pK a of DPPH has been reported to be 8.59. [11,42] The weakly acidic phenols (1 with pK a = 7.34 [43] or 7.62 [44,45] and 2 with pK a = 8.70 [43] ) give rise to fairly strong bases 3 and 4. Because only 3 (not 4) could be obtained in the solid state, denoted below by subscript (s), the reaction with DPPH was performed only with this phenol.…”

Section: The Reaction Of Dpph With the Sodium Aroxide 3 In The Presenmentioning

confidence: 99%

Reactions of 2,2‐Diphenyl‐1‐picrylhydrazyl (DPPH) with Two Syringylic Phenols or One Aroxide Derivative

et al. 2009

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The reactions between excess 2,2-diphenyl-1-picrylhydrazyl (DPPH) and either 4-hydroxy-3,5-dimethoxybenzaldehyde (syringaldehyde, 1) or methyl 4-hydroxy-3,5-dimethoxybenzoate (methyl syringate, 2) afford different products from those obtained with the corresponding aroxide (3) of 1. In the former case (with the free phenols) the aryloxy (syringyl) group substitutes the 4-nitro group of DPPH, yielding dinitro products 7 and 8 (new stable free radicals) and 9 and 10 (corresponding hydrazines), whereas in the latter case (with the

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Section: The Reaction Of Dpph With the Sodium Aroxide 3 In The Presenmentioning

confidence: 99%

Reactions of 2,2‐Diphenyl‐1‐picrylhydrazyl (DPPH) with Two Syringylic Phenols or One Aroxide Derivative

et al. 2009

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“…These results are probably based on the difference of anion effects; we have observed that anions with the larger crystal ionic radius cause the larger effects on the chemical shifts of water towards upper-field, as Cl À < NO 3 À < Br À < I À % ClO 4 À , in 2.0% 38 and 20 vol % EtOH-H 2 O solutions. 39 The 1 H NMR chemical shift can identify the presence of strong acids in reverse micelle systems, as well as in bulk water or bulk H 2 O-EtOH mixed solution. …”

Section: à3mentioning

confidence: 99%

Great Enhancement in the Oxidation Ability of Dilute Nitric Acid in Nanoscale Water-Droplets of Reverse Micelle Systems

Hojo¹,

Ueda²,

Daike³

et al. 2006

Bulletin of the Chemical Society of Japan

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In reverse micelle systems, a large enhancement of the oxidation ability of dilute nitric acid was discovered, and its oxidation mechanism was explored. The Br À ion in the surfactant, CTAB, was oxidized to Br 2 (or Br 3 À ) in the CHCl 3 / CTAB/H 2 O reverse micelle system with W ¼ 1:0{4:0 by diluted nitric acid (0.25-2.5 mol dm À3 in 1.0 vol % H 2 O portion) at 15-40 C where CTAB stands for cetyltrimethylammonium bromide, and the W value is the ratio of [. At higher concentrations of nitric acid and temperatures, faster reactions occurred. Otherwise, long reaction times were needed, e.g., 10 h for 1.0 mol dm À3 HNO 3 at 25 C. Light or ambient oxygen did not appear to affect the reaction. The ratio of produced Br 2 or (Br 3 À ) to the initial amount of HNO 3 indicated the following reaction scheme:The nitroyl ion (or nitronium ion), NO 2 þ , was proposed as the intermediate active species. The addition of HClO 4 as a proton source caused the complete reduction of N(V) as follows: The nitrate ion has high chemical stability, especially at low concentrations. Standard redox potentials indicate that it should serve as an excellent oxidizing agent, but in order to react with suitable reactants to form elemental nitrogen or ammonia, special conditions are required, such as the presence of catalysts and high temperature and pressure.1 Concentrated nitric acid has strong oxidation ability, although dilute nitric acid in aqueous solution at room temperature exhibits no apparent oxidation trend. Cotton and Wilkinson have described that nitric acid with a concentration of less than 2 mol dm À3 has almost no oxidation ability.2 Mixtures of concentrated nitric acid and sulfuric acid (''mixed acid'') are used for nitration of organic compounds, and the nitroyl ion (or nitronium ion) NO 2 þ is regarded as the active intermediate. 3 Raman spectra of NO 2 þ have been observed in solution 4 as well as in the solid state.5 Using 14 N NMR, Ross et al. 6 have examined the nitric acid/nitronium ion equilibrium in aqueous sulfuric acid. Dimeric nitric acid, (HNO 3 ) 2 or (DNO 3 ) 2 , was detected by FTIR in HNO 3 or DNO 3 :H 2 O:Ar matrices. 7 We have been studying the structure of water in nanoscale water-droplets of reverse micelles, stabilized by surfactants in organic solvents. 8 The size of the ''water-pool'' or ''water-droplet'' may vary from 1 to %100 8 It is well known that the properties of water localized in the interior of reverse micelles differ from those of bulk water, and the difference becomes progressively smaller as the amount of water in the micelle system increases.10

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“…NMR is a sensitive probe used for investigation of the electronic structure and intermolecular interactions, in particular hydrogen bonding interactions [4][5][6][7]. NMR of the 1-butyl-3-methylimidazolium tetrafluoroborate (BmimBF 4 ) and 1-butyl-3-methylimidazolium hexafluorophosphate (BmimPF 6 ) have been studied by Suarez et al, where they attributed the high chemical shifts of imidazolium protons to a hydrogen bond with the anions [8].…”

Section: Introductionmentioning

confidence: 99%

“…NMR of the 1-butyl-3-methylimidazolium tetrafluoroborate (BmimBF 4 ) and 1-butyl-3-methylimidazolium hexafluorophosphate (BmimPF 6 ) have been studied by Suarez et al, where they attributed the high chemical shifts of imidazolium protons to a hydrogen bond with the anions [8]. Holbrey and Seddon also used 1 H NMR to probe hydrogen bonding in the liquid phase for 1-alkyl-3-methylimidazolium tetrafluoroborate salts (C n mimBF 4 , n = 0-18); however, they found no significant H-bonding to anion, since the chemical shift values of…”

Section: Introductionmentioning

confidence: 99%

Nuclear magnetic resonance spectroscopic studies of the trihexyl (tetradecyl) phosphonium chloride ionic liquid mixtures with water

2008

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Tetra-alkyl Phosphonium ionic liquids are phosphonium salts with melting points near room temperature. We report the NMR studies of water-trihexyl (tetradecyl) phosphonium chloride ionic liquid mixtures. The proton chemical shifts were used to investigate the intermolecular interactions in mixtures of ionic liquids and water. The OH chemical shifts were found to decrease as the water concentration in the ionic liquid increased, and their rate of change with temperature decreased with water concentration. The CH 2 and CH 3 chemical shifts were found to move downfield with the increase in temperature, and moved further downfield as water concentration was decreased. The interface of experimental data and the results of quantum calculations suggest a significant binding of phosphonium cations to chloride anion and water molecules. As well, the analysis of the data suggests a possible transformation from cationchloride-water configuration at low water concentrations to cation-water-water at higher water concentrations.© Versita Warsaw and Springer-Verlag Berlin Heidelberg.

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Effects of Salts, Acids, and Phenols on the Hydrogen-Bonding Structure of Water−Ethanol Mixtures

Cited by 70 publications

References 32 publications

Reactions of 2,2‐Diphenyl‐1‐picrylhydrazyl (DPPH) with Two Syringylic Phenols or One Aroxide Derivative

Reactions of 2,2‐Diphenyl‐1‐picrylhydrazyl (DPPH) with Two Syringylic Phenols or One Aroxide Derivative

Great Enhancement in the Oxidation Ability of Dilute Nitric Acid in Nanoscale Water-Droplets of Reverse Micelle Systems

Nuclear magnetic resonance spectroscopic studies of the trihexyl (tetradecyl) phosphonium chloride ionic liquid mixtures with water

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