The Hydration of Ketones in Mixtures of Water and Polar Aprotic Solvents

1972 ◽  
Vol 50 (13) ◽  
pp. 1992-1999 ◽  
Author(s):  
Ross Stewart ◽  
John D. Van Dyke
Keyword(s):  
Activity Coefficient ◽  
Water Content ◽  
Equilibrium Constant ◽  
Carbonyl Group ◽  
Pure Water ◽  
Solvent Composition ◽  
Water Molecules ◽  
Aprotic Solvents ◽  
Acid Catalyzed

The hydration of a series of ring-substituted trifluoroacetophenones (Z) has been studied by means of u.v. and n.m.r. spectroscopy in DMSO–water and sulfolane–water mixtures. The W0 function is defined as [Formula: see text] where Kd is the equilibrium constant for the reaction [Formula: see text]Mixtures of water and sulfolane in all proportions have a dehydrating effect compared to water but mixtures of water and DMSO down to 15 mol % water are more hydrating with respect to the carbonyl group of trifluoroacetophenones than is pure water. An analysis of activity coefficient behavior indicates that the diol, ZH2O, has a higher requirement for solvation by water molecules than does water itself.The rate of the uncatalyzed hydration in aqueous sulfolane drops drastically as the water content of the medium decreases, whereas the rate of the acid-catalyzed reaction is not greatly affected by changes in the solvent composition; a plot of log k for both catalyzed and uncatalyzed reactions is approximately linear in W0.

Hydration of the carbonyl group — Acetic acid catalysis in the co-operative mechanism

2005 ◽  
Vol 83 (6-7) ◽  
pp. 769-785 ◽  
Author(s):  
Yih-Huang Hsieh ◽  
Noham Weinberg ◽  
Kiyull Yang ◽  
Chan-Kyung Kim ◽  
Zheng Shi ◽  
...  
Keyword(s):  
Acetic Acid ◽  
Carbonyl Group ◽  
Isotope Shift ◽  
Acid Catalysis ◽  
Water Molecules ◽  
Hydration Reaction ◽  
Water Solvent ◽  
General Acid ◽  
O Isotope ◽  
Acid Catalyzed

In a co-operative reaction, solvent molecules, specifically water molecules, participate actively in the mechanism to circumvent the formation of charged intermediates. This paper extends our earlier theoretical treatment of the neutral co-operative hydration of acetone to include general acid catalysis by acetic acid. As before, the predominant neutral channel employs three catalytic water molecules. The principal acetic acid catalyzed channels employ one catalytic water molecule and, in approximately equal proportions, one or both oxygens of the carboxyl group. The theoretical rate constant for general acid catalysis is calculated to be 0.49 M–1 s–1 at 298 K. This compares to an estimated experimental value of 0.30 M–1 s–1 for acetic acid catalyzed hydration of acetone at 298 K in water solvent, determined by using the 18O-isotope shift in the 13C NMR spectrum of 2-13C-labelled acetone as a kinetic probe. It is concluded that the notion of co-operativity can be extended to include general acid catalysis of the hydration of a carbonyl group in water solvent. This creates an obvious problem for the generally accepted view that multistep ionic mechanisms are operative in the low dielectric media that exist at the active sites of hydrolytic enzymes. The relevance of this finding to the mechanisms of action of β-lactam antibiotics has been noted.Key words: hydration, reaction mechanism, co-operativity, general acid catalysis, ab initio, SCRF, 18O-isotope shift.

The Mutarotation of Glucose in Dimethylsulfoxide and Water Mixtures

1973 ◽  
Vol 51 (4) ◽  
pp. 556-564 ◽  
Author(s):  
N. M. Ballash ◽  
E. B. Robertson
Keyword(s):  
Transition State ◽  
Activation Parameters ◽  
Solvent Composition ◽  
Water Molecules ◽  
Solvent Mixtures ◽  
Cyclic Transition ◽  
Proton Transfers ◽  
Poor Region ◽  
Cyclic Transition State ◽  
Acid Catalyzed

The mutarotation of glucose is a general acid – base-catalyzed reaction which involves two proton transfers. Whether these proton transfers are carried out in a stepwise or concerted manner, the latter alternative possibly incorporating several water molecules in a cyclic transition state, is not known with certainty.This study was undertaken in an attempt to clarify the mechanism by determining directly the number of water molecules participating in the transition state. The method chosen was to determine rates for the acid-catalyzed mutarotation of glucose as a function of solvent composition in dimethylsulfoxide and water mixtures, particularly in the water poor region. The results show that for the acid-catalyzed reaction the order with respect to water is zero. For water catalysis, the results are less reliable but suggest that about three water molecules may be involved. These facts are interpreted to mean that a stepwise mechanism is operative in the proton-catalyzed reaction, but that the solvent-catalyzed process may involve a cyclic concerted mechanism.Rate measurements were also carried out as a function of temperature for various solvent mixtures. The calculated activation parameters remain practically constant over the solvent composition region and attest to the constancy of the mechanism over this range. Thus the results which pertain strictly to solutions of high dimethylsulfoxide content should apply to aqueous solutions as well.

Infrared titration of aqueous NaOH by aqueous HCl

2000 ◽  
Vol 78 (1) ◽  
pp. 64-72 ◽  
Author(s):  
Jean-Joseph Max ◽  
Camille Chapados
Keyword(s):  
Factor Analysis ◽  
Activity Coefficient ◽  
Pure Water ◽  
Strong Association ◽  
Alkaline Solutions ◽  
Water Molecules ◽  
Mean Activity Coefficient ◽  
Infrared Spectral ◽  
Ir Analysis ◽  
The Mean

The titration of NaOH by HCl is achieved through infrared spectral measurement of the various mixtures. Factor Analysis (FA) is used to separate the spectra. Four principal spectra were necessary to perform the analysis: pure water, 2.09 M HCl, 2.23 M NaOH, and 2.60 M NaCl solvated water. Each of the 18 experimental spectra obtained was determined to be a linear combination of these principal spectra. The composition of the solutions retrieved from the IR analysis is identical to what was determined by the mass balance. The mean activity coefficient of HCl was calculated using the concentration of HCl obtained by IR and the activity obtained by pH measurements. It was found that the mean activity coefficient increased by a factor greater than 2 in the presence of 1 M NaCl. Because the water molecules associated to the ionic pair H+/Cl-, as observed by IR, are unmodified by the presence of the salt, such an increase cannot be attributed to a modification of the strong association of the water molecules to the pair of ions.Key words: infrared spectroscopy; ATR; liquid; acidic solutions; alkaline solutions; aqueous solutions; factor analysis; principal spectra; HCl-, NaOH-, NaCl-solvated water; activity coefficient; IR titration.

Calculation of Equilibrium Constant for Dimerization of Heavy Water Molecules in Saturated Vapor

2015 ◽  
Vol 60 (3) ◽  
pp. 263-267
Author(s):  
L.A. Bulavin ◽  
◽  
S.V. Khrapatyi ◽  
V.M. Makhlaichuk ◽  
Keyword(s):  
Equilibrium Constant ◽  
Heavy Water ◽  
Saturated Vapor ◽  
Water Molecules

CONDUCTANCES OF LITHIUM NITRATE SOLUTIONS IN ETHYL ALCOHOL AND ETHYL ALCOHOL - WATER MIXTURES AT 25.0 °C.

1956 ◽  
Vol 34 (9) ◽  
pp. 1232-1242 ◽  
Author(s):  
A. N. Campbell ◽  
G. H. Debus
Keyword(s):  
No Value ◽  
Ethyl Alcohol ◽  
Pure Water ◽  
Lithium Ion ◽  
Water Molecules ◽  
Lithium Nitrate ◽  
Absolute Alcohol ◽  
Pure Alcohol ◽  
Alcohol Water ◽  
Nitrate Solutions

The conductances of solutions of lithium nitrate in 30, 70, and 100 weight per cent ethyl alcohol have been determined at concentrations ranging from 0.01 molar up to saturation, at 25 °C. The densities and viscosities of these solutions have also been determined. The data have been compared with the calculated conductances obtained from the Wishaw–Stokes equation. The agreement is fairly good up to, say, 2 M, for all solvents except absolute alcohol. In the latter solvent there is no value of å, the distance of closest approach, which will give consistent values of the equivalent conductance. In passing from pure water to pure alcohol, the value of å increases progressively and this we attribute to a change in the solvation of the lithium ion from water molecules to alcohol molecules. Some further calculations incline us to the view that the nitrate ion, as well as the lithium ion, is solvated to some extent, at least in alcohol.

scholarly journals Effect of solvent composition on the critical micelle concentration of sodium deoxycholate in ethanol-water mixed solvent media

BIBECHANA ◽  
2012 ◽  
Vol 9 ◽  
pp. 63-68 ◽  
Author(s):  
Ajaya Bhattarai ◽  
Sujit Kumar Shah ◽  
Ashok Kumar Yadav ◽  
Janak Adhikari
Keyword(s):  
Critical Micelle Concentration ◽  
Precise Measurement ◽  
Mixed Solvent ◽  
Volume Fraction ◽  
Pure Water ◽  
Specific Conductivity ◽  
Sodium Deoxycholate ◽  
Solvent Composition ◽  
Effect Of Solvent

The precise measurement of the specific conductivity of sodium deoxycholate in pure water and ethanolwater mixed solvent media containing 0.10 and 0.20 volume fraction of ethanol at 303.15 K are reported. The concentration were varied from ~ 0.01 mol L-1 to ~ 0.0002 mol L-1.The conductivity of sodium deoxycholate decreases with the increase in the volume fraction of ethanol. The critical micelle concentration of sodium deoxycholate increases with the increase in the volume fraction of ethanol. DOI: http://dx.doi.org/10.3126/bibechana.v9i0.7176 BIBECHANA 9 (2013) 63-68

Hydration States of Cholinium Phosphate-Type Ionic Liquids as a Function of Water Content

2019 ◽  
Vol 72 (5) ◽  
pp. 392 ◽  
Author(s):  
Yohsuke Nikawa ◽  
Seiji Tsuzuki ◽  
Hiroyuki Ohno ◽  
Kyoko Fujita
Keyword(s):  
Ionic Liquids ◽  
Water Content ◽  
Alkyl Chain ◽  
Hydroxyl Group ◽  
Water Molecules ◽  
Hydroxyl Groups ◽  
Ion Structure ◽  
Activity Measurements ◽  
Microscopic Interactions ◽  
Dynamics Simulations

We investigated the hydration states of cholinium phosphate-type ionic liquids (ILs) in relation to ion structure, focusing on the influence of the hydroxyl group of the cation and the alkyl chain length of the anion. Water activity measurements provided information on the macroscopic hydration states of the hydrated ILs, while NMR measurements and molecular dynamics simulations clearly showed the microscopic interactions and coordination of the water molecules. The hydrogen bonding networks in these ILs were influenced by the anion structure and water content, and the mobility of water molecules was influenced by the number of hydroxyl groups in the cation and anion.

scholarly journals Effect of Solvent Composition on the Critical Micelle Concentration of Cetylpyridinium Chloride in Ethanol-Water Mixed Solvent Media

2013 ◽  
Vol 13 (1) ◽  
pp. 89-93 ◽  
Author(s):  
Ajaya Bhattarai ◽  
Sujit Kumar Shah ◽  
Ashok Kumar Yadav
Keyword(s):  
Critical Micelle Concentration ◽  
Room Temperature ◽  
Mixed Solvent ◽  
Volume Fraction ◽  
Science And Technology ◽  
Pure Water ◽  
Specific Conductivity ◽  
Cetylpyridinium Chloride ◽  
Solvent Composition ◽  
Effect Of Solvent

The accurate measurement of the specific conductivity of cetylpyridinium chloride in pure water and ethanol-water mixed solvent media containing 0.10, 0.20, 0.30 and 0.40 volume fraction of ethanol at room temperature are reported. The concentrations were varied from ~ 0.005 mol l-1 to ~ 0.0002 mol l-1.The conductivity of cetylpyridinium chloride decreases with the increase in the volume fraction of ethanol. The critical micelle concentration of cetylpyridinium chloride increases with the increase in the volume fraction of ethanol. Nepal Journal of Science and Technology Vol. 13, No. 1 (2012) 89-93 DOI: http://dx.doi.org/10.3126/njst.v13i1.7446

Stereodivergent synthesis of 1,4-dicarbonyls by traceless charge–accelerated sulfonium rearrangement

Science ◽  
2018 ◽  
Vol 361 (6403) ◽  
pp. 664-667 ◽  
Author(s):  
Dainis Kaldre ◽  
Immo Klose ◽  
Nuno Maulide
Keyword(s):  
Natural Products ◽  
Double Bond ◽  
Carbonyl Group ◽  
Organic Synthesis ◽  
Relative Configuration ◽  
Chiral Induction ◽  
Tremendous Importance ◽  
Acid Catalyzed ◽  
Quaternary Stereocenters ◽  
Drug Scaffolds

The chemistry of the carbonyl group is essential to modern organic synthesis. The preparation of substituted, enantioenriched 1,3- or 1,5-dicarbonyls is well developed, as their disconnection naturally follows from the intrinsic polarity of the carbonyl group. By contrast, a general enantioselective access to quaternary stereocenters in acyclic 1,4-dicarbonyl systems remains an unresolved problem, despite the tremendous importance of 2,3-substituted 1,4-dicarbonyl motifs in natural products and drug scaffolds. Here we present a broad enantioselective and stereodivergent strategy to access acyclic, polysubstituted 1,4-dicarbonyls via acid-catalyzed [3,3]-sulfonium rearrangement starting from vinyl sulfoxides and ynamides. The stereochemistry at sulfur governs the absolute sense of chiral induction, whereas the double bond geometry dictates the relative configuration of the final products.

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