Acid-catalyzed Hydrolysis of Methylal. I. Influence of Strong Acids and Correlation with Hammett Acidity Function

1954 ◽  
Vol 76 (12) ◽  
pp. 3240-3242 ◽  
Author(s):  
Donald McIntyre ◽  
F. A. Long
Keyword(s):  
Acidity Function ◽  
Hammett Acidity Function ◽  
Acid Catalyzed ◽  
Strong Acids ◽  
Hydrolysis Of

THE ACID HYDROLYSIS OF GLYCOSIDES: I. GENERAL CONDITIONS AND THE EFFECT OF THE NATURE OF THE AGLYCONE

1964 ◽  
Vol 42 (6) ◽  
pp. 1456-1472 ◽  
Author(s):  
T. E. Timell
Keyword(s):  
Acid Hydrolysis ◽  
Equilibrium Concentration ◽  
Rate Coefficients ◽  
Acidity Function ◽  
Tertiary Alcohols ◽  
Conjugate Acid ◽  
Rate Of Hydrolysis ◽  
Acid Catalyzed ◽  
Opposing Effects ◽  
Hydrolysis Of

First-order rate coefficients and energies and entropies of activation have been determined for the acid-catalyzed hydrolysis of a number of methyl D-glycopyranosides and disaccharides. The relation between the logarithm of the rate coefficients and values for Hammett's acidity function was linear, although different for different acids. All compounds had entropies of activation indicating a unimolecular reaction mechanism. Glucosides of tertiary alcohols were hydrolyzed very rapidly, triethylmethyl β-D-glucopyranoside, for example, 30,000 times taster than the corresponding methyl compound.Increase in size of the aglycone caused a slight increase in the rate of hydrolysis of β-D-glucopyranosides, steric hindrance thus being of no significance. Electron-attracting substituents in the aglycone had little or no influence on the rate of hydrolysis, obviously because they would tend to lower the equilibrium concentration of the conjugate acid, while facilitating the subsequent heterolysis, the two opposing effects more or less cancelling out. These results were discussed in connection with recent studies on the acid hydrolysis of various phenyl glycopyranosides and with reference to the postulated occurrence of an activating inductive effect in oligo- and poly-saccharides containing carboxyl or other electronegative groups at C-5. It was concluded that there is little evidence for the existence of any such effect and that, for example, pseudoaldobiouronic acids should be hydrolyzed at the same rate as corresponding neutral disaccharides.

Kinetics and mechanism of hydrolysis of 3-diazobenzofuran-2-one and its hydrolysis product (3-hydroxybenzofuran-2-one)

2002 ◽  
Vol 80 (1) ◽  
pp. 82-88
Author(s):  
Y Chiang ◽  
A J Kresge ◽  
Q Meng
Keyword(s):  
Acid Catalysis ◽  
Hydrolysis Product ◽  
Diazo Compound ◽  
Acidity Function ◽  
Hydroxide Ion ◽  
Mechanism Of Hydrolysis ◽  
Acid Catalyzed ◽  
Catalyzed Reactions ◽  
Rate Profile ◽  
Hydrolysis Of

Rates of acid-catalyzed hydrolysis of 3-diazobenzofuran-2-one, measured in concentrated aqueous perchloric acid and hydrochloric acid solutions, were found to correlate well with the Cox–Yates Xo excess acidity function, giving kH+ = 1.66 × 10–4 M–1 s–1, m‡ = 0.86 and kH+ /kD+ = 2.04. The normal direction (kH/kD > 1) of this isotope effect indicates that hydrolysis occurs by rate-determining protonation of the substrate on its diazo-carbon atom. It was found previously that the next higher homolog of the present substrate, 4-diazoisochroman-3-one, also undergoes hydrolysis by this reaction mechanism but with a rate constant 15 times greater than that for the present substrate; this difference in reactivity can be understood in terms of the various resonance forms that contribute to the structures of these substrates. The product of the present hydrolysis reaction is 3-hydroxybenzofuran-2-one, which itself quickly undergoes subsequent acid-catalyzed hydrolysis to 2-hydroxymandelic acid. The acidity dependence of this subsequent hydrolysis is much shallower than that of the diazo compound precursor, and rates of reaction correlate as well with [H+] as with Xo. This is due in part to incursion of a nonproductive protonation on the hydroxy group of 3-hydroxy benzo furan-2-one that impedes hydrolysis and produces saturation of acid catalysis. Rates of hydrolysis of the hydroxy compound were also measured in dilute HClO4 and NaOH solutions as well as in CH3CO2H, H2PO4–, (CH2OH)3CNH3+, and NH4+ buffers, and the rate profile constructed from these data showed the presence of uncatalyzed and hydroxide ion-catalyzed reactions. This hydroxide-ion catalysis became saturated at [NaOH] [Formula: see text] 0.05 M, implying occurrence of yet another nonproductive substrate ionization. Key words: diazo compound hydrolysis, lactone hydrolysis, Cox–Yates excess acidity, acid catalysis, alcohol protonation.

PRESSURE EFFECT AND MECHANISM IN ACID CATALYSIS: IV. THE HYDROLYSIS OF DIETHYL ETHER

1959 ◽  
Vol 37 (4) ◽  
pp. 788-794 ◽  
Author(s):  
J. Koskikallio ◽  
E. Whalley
Keyword(s):  
Diethyl Ether ◽  
Acid Catalysis ◽  
Pressure Effect ◽  
Slow Step ◽  
Acidity Function ◽  
Temperature Range ◽  
Entropy Of Activation ◽  
Acid Catalyzed ◽  
Hydrolysis Of

The acid-catalyzed hydrolysis of diethyl ether has been measured in the temperature range 120–160 °C at low acid concentrations; the entropy of activation is −9.0 ± ~2.5 cal deg−1 mole−1. The effect of pressures up to 3000 atm has been measured at 161.2 °C; the volume of activation at 1 atm is −8.5 ± ~2 cm3 mole−1. These two results show that the slow step is bimolecular. The rate in concentrated acids was measured at 119 °C; the rate was much more nearly proportional to the acidity function h0 than to concentration of acid. This is contrary to the predictions of the Zucker–Hammett hypothesis, which is therefore not valid for the hydrolysis of diethyl ether.

The Wallach rearrangement. Part V. Acid catalyzed hydrolysis of azobenzene-4-hydrogen sulfate

1969 ◽  
Vol 47 (6) ◽  
pp. 911-917 ◽  
Author(s):  
E. Buncel ◽  
W. M. J. Strachan
Keyword(s):  
Potassium Salt ◽  
Reactive Species ◽  
Acidity Function ◽  
Hydrogen Sulfate ◽  
Sulfate Salt ◽  
Acid Media ◽  
Phenolic Oxygen ◽  
Acidic Conditions ◽  
Acid Catalyzed ◽  
Hydrolysis Of

In relation to the intermediacy of azobenzene-4-hydrogen sulfate in the Wallach rearrangement of azoxybenzene, the potassium salt has been characterized and subjected to examination under acidic conditions. A pKa value of −2.14 has been obtained, for N-protonation. The sulfate salt hydrolyzes to p-hydroxyazobenzene in acid media and the rate of the reaction has been measured over the region 22–42% H2SO4 at 25° spectrophotometrically. A correlation between rate and acidity function indicates that a two-proton process is involved; a reactive species is proposed having a nitrogen and the phenolic oxygen protonated. The relevance of these findings to Wallach rearrangement studies is discussed.

A General Relation Between H0, Acid Concentration, and Water Activity for Strong Acids at Moderate Concentrations

1972 ◽  
Vol 50 (20) ◽  
pp. 3283-3287 ◽  
Author(s):  
T. T. Teng ◽  
F. Lenzi
Keyword(s):  
Equilibrium Constants ◽  
General Relation ◽  
Type Equation ◽  
Strong Acid ◽  
Acidity Function ◽  
Acid Anion ◽  
Degree Of Dissociation ◽  
Hammett Acidity Function ◽  
Hydrated Proton ◽  
Strong Acids

Values of the Hammett acidity function H0 can be correlated for strong acid solutions up to −H0 values of 3.5 via a Bascombe and Bell type equation:[Formula: see text] taking into account the degree of dissociation of the acids. This can be interpreted according to[Formula: see text]and[Formula: see text]Alternatively, an approach based on the treatment of equilibrium constants in terms of mole-fractions yields[Formula: see text]valid for the same acids (H2SO4, HClO4, HCl, and HNO3) and again involving a tri-dehydration of the tetra-hydrated proton. The log of the ratio [Formula: see text] has been found to be proportional to −H0 itself and to be otherwise independent of the nature of the acid anion.

scholarly journals Relations between the Hammett Acidity Function, H0, and Ion Activities in Mixtures of strong Acids and Water.

1960 ◽  
Vol 14 ◽  
pp. 1627-1642 ◽  
Author(s):  
Erik Högfeldt ◽  
Niels Hofman-Bang ◽  
Thor A. Bak ◽  
E. Varde ◽  
Gertrud Westin
Keyword(s):  
Acidity Function ◽  
Hammett Acidity Function ◽  
Ion Activities ◽  
Strong Acids

Hammett acidity function of water-salt solutions of strong acids

1989 ◽  
Vol 38 (11) ◽  
pp. 2234-2237 ◽  
Author(s):  
S. G. Sysoeva ◽  
I. S. Kislina ◽  
M. I. Vinnik
Keyword(s):  
Acidity Function ◽  
Salt Solutions ◽  
Hammett Acidity Function ◽  
Water Salt ◽  
Strong Acids

Preparation and Characterization of a Novel Room Temperature Dicationic Ionic Liquid and its Application in the Synthesis of Xanthenediones Under Solvent-Free Conditions

2018 ◽  
Vol 21 (8) ◽  
pp. 602-608 ◽  
Author(s):  
Zainab Ehsani-Nasab ◽  
Ali Ezabadi
Keyword(s):  
Ionic Liquid ◽  
Room Temperature ◽  
Reaction Times ◽  
Significant Loss ◽  
Solvent Free ◽  
Acidity Function ◽  
Efficient Catalyst ◽  
Solvent Free Conditions ◽  
Hammett Acidity Function ◽  
Dicationic Ionic Liquid

Aim and Objective: In the present work, 1, 1’-sulfinyldiethylammonium bis (hydrogen sulfate) as a novel room temperature dicationic ionic liquid was synthesized and used as a catalyst for xanthenediones synthesis. Material and Method: The dicationic ionic liquid has been synthesized using ethylamine and thionyl chloride as precursors. Then, by the reaction of [(EtNH2)2SO]Cl2 with H2SO4, [(EtNH2)2SO][HSO4]2 was prepared and after that, it was characterized by FT-IR, 1H NMR, 13C NMR as well as Hammett acidity function. This dicationic ionic liquid was used as a catalyst for the synthesis of xanthenediones via condensation of structurally diverse aldehydes and dimedone under solvent-free conditions. The progress of the reaction was monitored by thin layer chromatography (ethyl acetate/n-hexane = 3/7). Results: An efficient solvent-free method for the synthesis of xanthenediones has been developed in the presence of [(EtNH2)2SO][HSO4]2 as a powerful catalyst with high to excellent yields, and short reaction times. Additionally, recycling studies have demonstrated that the dicationic ionic liquid can be readily recovered and reused at least four times without significant loss of its catalytic activity. Conclusion: This new dicationic ionic liquid can act as a highly efficient catalyst for xanthenediones synthesis under solvent-free conditions.

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