ChemInform Abstract: FRACTIONATION FACTORS FOR THE AQUEOUS HYDROXIDE ION AND SOLVENT ISOTOPE EFFECTS ON THE IONIZATION OF 1,8-BIS(DIMETHYLAMINO)NAPHTHALENE (PROTON SPONGE)

1981 ◽  
Vol 12 (12) ◽  
Author(s):  
Y. CHIANG ◽  
A. J. KRESGE ◽  
R. A. MORE O'FERRALL
Keyword(s):  
Isotope Effects ◽  
Proton Sponge ◽  
Hydroxide Ion ◽  
Solvent Isotope ◽  
Solvent Isotope Effects ◽  
Fractionation Factors

Phosphato complexes of cobalt(III). IV. Hydrolysis in basic solution

1968 ◽  
Vol 21 (7) ◽  
pp. 1733 ◽  
Author(s):  
SF Lincoln ◽  
DR Stranks
Keyword(s):  
Isotope Effects ◽  
Base Hydrolysis ◽  
Basic Solution ◽  
Tracer Technique ◽  
Hydroxide Ion ◽  
Solvent Water ◽  
Coordination Spheres ◽  
Solvent Isotope ◽  
Hydrolysis Of ◽  
Solvent Isotope Effects

The rates of hydrolysis of phosphato complexes of cobalt(111) in sodium hydroxide concentrations ranging from 0.02M to 0.37M, and at several ionic strengths, have been measured with a tracer technique. Bidentate phosphato complexes exhibit the same rates of hydrolysis as the corresponding monodentate complexes, due to a rapid conversion of the bidentate into the monodentate form. The general rate law for base hydrolysis of all the phosphato complexes is: d[PO34]/dt = {kH2O + kOH[OH-]}[complex] At 60� and at unit ionic strength, the rate constants for the complexes cis-[Co(NH3)4OH.PO4]-, cis-[Co en2OH.PO4]-, and [Co(NH3)5PO4] respectively are: 103kH2O (min-l) 85.0, 2.0, <1; and 103kOH (1. mole-1 min-l) 42.7, 12.0, 69.5. Mechanistic conclusions have been based on the measured enthalpies and entropies of activation and deuterium solvent isotope effects. For all complexes, kH2O is identified with an aquation mechanism involving synchronous interchange of the phosphate and solvent water between the first and second coordination spheres of the complexes. In the case of the tetrammine and bis(ethylenediamine) complexes, kOH is identified with a process involving synchronous interchange of phosphate and hydroxide ion between the first and second coordination spheres of the complexes. In the case of the pentammine complex, an SN2CB mechanism is considered to be more probable. A comparison with the base hydrolysis of halogen complexes of cobalt(111) is presented.

Correlation of rates of uncatalyzed and hydroxide-ion catalyzed ketene hydration. A mechanistic application and solvent isotope effects on the uncatalyzed reaction

2000 ◽  
Vol 78 (4) ◽  
pp. 508-515
Author(s):  
John Andraos ◽  
A Jerry Kresge
Keyword(s):  
Carbon Atom ◽  
Rate Constants ◽  
Isotope Effects ◽  
Nucleophilic Attack ◽  
Carbonyl Carbon Atom ◽  
Basic Solution ◽  
Carbonyl Carbon ◽  
Hydroxide Ion ◽  
Solvent Isotope ◽  
Solvent Isotope Effects

Rates of hydration of a number of ketenes were measured in neutral and basic solution using flash photolytic techniques, and rate constants for their uncatalyzed, kuc, and hydroxide-ion catalyzed, kHO, reactions were determined. These results, plus additional data from the literature, were found to provide the remarkably good correlation log kuc = -3.21 + 1.14 log kHO, which spans 10 orders of magnitude in reactivity and includes 31 ketenes. This good correlation implies that uncatalyzed and hydroxide-ion catalyzed ketene hydraton occur by similar reaction mechanisms, which for the hydroxide-ion catalyzed process is known to involve nucleophilic attack on the carbonyl carbon atom of the ketene. Rate constants for phenylhydroxyketene, on the other hand, do not fit this correlation, which suggests that the mechanistic assignment upon which these rate constants are based may not be correct. Solvent isotope effects on these uncatalyzed ketene hydrations are weak; most are less than kH/kD = 2. It is argued that these isotope effects are largely, if not entirely, secondary in nature and that they are consistent with both a reaction mechanism in which nucleophlic attack of a single water molecule on the ketene carbonyl carbon atom produces a zwitterionic intermediate and also a mechanism that avoids this intermediate by passing through a cyclic transition state involving several water molecules.Key words: ketene hydration, rate correlation, nucleophilic attack, solvent isotope effects, phenylhydroxyketene.

Article

1999 ◽  
Vol 77 (4) ◽  
pp. 459-462
Author(s):  
J Andraos ◽  
Y Chiang ◽  
S J Eustace ◽  
A J Kresge ◽  
S W Paine ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Carbonyl Group ◽  
Flash Photolysis ◽  
Isotope Effects ◽  
Nucleophilic Attack ◽  
Hydroxide Ion ◽  
Solvent Isotope ◽  
Solvent Isotope Effects

Five ketenes, phenyl(ethyl)ketene, phenyl(methylthio)ketene, diphenylketene, pentafluorophenylketene, and 1-naphthylketene, were generated flash photolytically and solvent isotope effects (H2O vs. D2O) on their hydroxide-ion-catalyzed hydration in aqueous solution were determined. The values obtained are all weakly inverse and closely similar (kHO/kDO = 0.76-0.97), as expected for these fast, hydroxide-ion-consuming reactions, known to proceed by nucleophilic attack of hydroxide on the ketene carbonyl group. The characteristic magnitude of these isotope effects should prove useful in identifying new examples of this reaction.Key words: ketenes, flash photolysis, photo-Wolff reaction, solvent isotope effects on hydroxide ion consumption.

Medium isotope effect for isobutyrophenone in aqueous solution. Solvent isotope effects on carbonyl group hydration

1989 ◽  
Vol 67 (5) ◽  
pp. 792-793 ◽  
Author(s):  
J. R. Keeffe ◽  
A. J. Kresge
Keyword(s):  
Isotope Effect ◽  
Deuterium Oxide ◽  
Isotope Effects ◽  
Hydroxyl Group ◽  
Hydroxyl Groups ◽  
Solvent Isotope Effect ◽  
Fractionation Factor ◽  
Solvent Isotope ◽  
Solvent Isotope Effects ◽  
Fractionation Factors

A medium solvent isotope effect of Φ = 0.827 ± 0.013 was determined for transfer of isobutyrophenone from H2O to D2O. This result, in conjunction with the average solvent isotope effect on hydration of a number of carbonyl compounds, leads to [Formula: see text] as the fractionation factor for the hydroxyl group hydrogens of the hydration reactions' gem-diol products, which is consistent with the expectation that fractionation factors for uncharged hydroxyl groups should be unity. Keywords: isobutyrophenone, fractionation factors, solvent isotope effects, deuterium oxide.

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