Acid-catalyzed enolization of acetophenone: catalysis by bisulfate ion in sulfuric acid solutions

1986 ◽  
Vol 64 (6) ◽  
pp. 1224-1227 ◽  
Author(s):  
J. R. Keeffe ◽  
A. J. Kresge ◽  
J. Toullec
Keyword(s):  
Aqueous Solution ◽  
Sulfuric Acid ◽  
Acidity Constant ◽  
Acidity Function ◽  
Acid Solutions ◽  
Dilute Aqueous Solution ◽  
Acid Catalyzed ◽  
The Difference ◽  
Carbon Acid ◽  
Sulfuric Acid Solutions

Rates of acid-catalyzed enolization of acetophenone in dilute aqueous solution, measured under conditions where the solvated proton is the only acidic species present, give a hydrogen ion catalytic coefficient, [Formula: see text], that is 35% smaller than the value obtained by X acidity function extrapolation of measurements made in moderately concentrated sulfuric acid solutions. The difference may be attributed to catalysis by bisulfate ion in the sulfuric acid solutions; this is supported by direct measurement of the bisulfate ion catalytic coefficient in dilute sulfuric acid. This revised value of [Formula: see text] leads to new, but only slightly different, values of the keto–enol equilibrium constant for acetophenone in aqueous solution, pKE = 7.96 ± 0.04, the acidity constant for acetophenone ionizing as a carbon acid, [Formula: see text] and the encounter-controlled rate constant for the reaction of acetophenone enol with molecular bromine, k = (3.2 ± 0.4) × 109 M−1 s−1.

scholarly journals Mechanisms of Thioacylal Hydrolysis in Sulfuric Acid Solutions

1975 ◽  
Vol 53 (18) ◽  
pp. 2772-2780 ◽  
Author(s):  
Robert Allan McClelland
Keyword(s):  
Sulfuric Acid ◽  
Nitro Compound ◽  
Ester Hydrolysis ◽  
Acid Solutions ◽  
Hydrolysis Mechanism ◽  
Acid Catalyzed ◽  
Sulfuric Acid Solutions ◽  
Electron Withdrawing Substituents

The acid-catalyzed hydrolysis (aqueous H2SO4) of thioacylalsCH3SCH2OAc and ArSCH2OAc is reported. The former is shown to react solely by an A-1 mechanism proceeding via an intermediate CH3SCH2+ cation. In the latter series hydrolysis in dilute acids involves both this A-1 mechanism and a normal AAc-2 ester hydrolysis mechanism occurring simultaneously; as the acidity is increased the proportion of A-1 reaction increases until it completely dominates. The A-1 reaction shows lesser importance with electron-withdrawing substituents. The 4-nitro compound in fact shows no A-1 mechanism until about 40% H2SO4. These hydrolyses are compared with those of the corresponding acylals, which show a similar mechanistic behavior. Relative A-1 reactivities for RXCH2OAc, RX = CH3O, CH3S, C6H5S, C6H5O are 81, 49, 1, 0.022, relative to C6H5SCH2OAc. Discussions pertaining to the effects of the oxygen and the sulfur in these systems are presented.

Protonation of conjugated carbonyl groups in sulfuric acid solutions. III. α,β-Unsaturated ketosteroids

1970 ◽  
Vol 48 (16) ◽  
pp. 2538-2541 ◽  
Author(s):  
R. I. Zalewski ◽  
G. E. Dunn
Keyword(s):  
Sulfuric Acid ◽  
Spectral Data ◽  
Acidity Function ◽  
Additive Effects ◽  
Acid Solutions ◽  
Carbonyl Groups ◽  
Ultraviolet Spectrophotometry ◽  
Unit Slope ◽  
Straight Lines ◽  
Sulfuric Acid Solutions

Protonation of 20 α,β-unsaturated ketosteroids by sulfuric acid was studied by ultraviolet spectrophotometry. Plots of log [B]/[BH+] from spectral data against the amide acidity function, HA, gave straight lines with unit slope. The pKBH+ values thus obtained show the same additive effects of substituents as that reported previously for simple α,β-unsaturated alicyclic ketones.

The Mechanism of Bromination of 2(1H)-Pyrimidinone, its N-Methyl and N,N′-Dimethyl Derivatives in Aqueous Acidic Solution

1974 ◽  
Vol 52 (3) ◽  
pp. 451-457 ◽  
Author(s):  
Oswald S. Tee ◽  
Sujit Banerjee
Keyword(s):  
Sulfuric Acid ◽  
Acidic Solution ◽  
Acid Solutions ◽  
Aqueous Sulfuric Acid ◽  
Acid Catalyzed ◽  
Aqueous Acidic Solution ◽  
Sulfuric Acid Solutions

Rates of bromination at the 5-positions of the title compounds have been measured in aqueous sulfuric acid solutions. The reaction involves a rapid irreversible formation of a 5-bromo-4,6-dihydroxy-hexahydro-2-oxopyrimidine which undergoes slow acid-catalyzed conversion to the corresponding 5-bromopyrimidinone. If excess bromine is present the latter product reacts further to produce a 5,5-dibromo-4,6-dihydroxyhexahydropyrimidine.

The ketonization of acetophenone enol in concentrated aqueous sulphuric and perchloric acid solutions. Implication on X acidity function correlations of the enolization reaction and determination of the keto–enol equilibrium constant as a function of acidity

1990 ◽  
Vol 68 (10) ◽  
pp. 1653-1656 ◽  
Author(s):  
Y. Chiang ◽  
A. J. Kresge ◽  
R. A. More O'ferrall ◽  
B. A. Murray ◽  
N. P. Schepp ◽  
...  
Keyword(s):  
Sulfuric Acid ◽  
Key Words ◽  
Equilibrium Constant ◽  
Perchloric Acid ◽  
Acidity Function ◽  
Acid Solutions ◽  
Function Correlation ◽  
Aqueous Perchloric Acid ◽  
Sulfuric Acid Solutions

Rates of ketonization of the enol of acetophenone, generated by flash photolytic photohydration of phenylacetylene, were measured in aqueous sulfuric and perchloric acid solutions over the concentration range 1–50 wt.% acid; rates of enolization of acetophenone, monitored by bromine scavenging, were also measured in aqueous perchloric acid solutions over the same concentration range. The results suggest that the curvature observed in a previous X acidity function correlation of the rate of enolization in sulfuric acid solutions was an artifact produced by insufficiently efficient scavenging, and that introduction of the activity of water in the correlating expression, used previously to eliminate the curvature and believed to reflect covalent involvement of water in the enolization reaction, is unnecessary. The present results also show that the keto–enol equilibrium constant for acetophenone decreases with increasing acidity in these concentrated sulfuric and perchloric acid solutions. Key words: acetophenone, enolization, ketonization, keto–enol equilibrium, concentrated acid solutions.

Mechanisms of Acylal Hydrolysis in Sulfuric Acid Solutions

1975 ◽  
Vol 53 (18) ◽  
pp. 2763-2771 ◽  
Author(s):  
Robert Allan McClelland
Keyword(s):  
Sulfuric Acid ◽  
Ester Hydrolysis ◽  
Acid Solutions ◽  
Acetate Esters ◽  
Hydrolysis Mechanism ◽  
Tert Butyl ◽  
Acid Catalyzed ◽  
Sulfuric Acid Solutions

The acid-catalyzed hydrolysis (in aqueous H2SO4) of acylals ArOCH2OAc is reported, and compared with that of normal acetate esters. On the basis of r plot behavior and the effects of the aromatic substituents, an AAc-2 ester hydrolysis mechanism is shown to occur in dilute acids, with a changeover to a mechanism analogous to AA1-1 ester hydrolysis (intermediate cation ArOCH2+) in more concentrated acids, the position of the changeover being dependent on the substituent. Methylene diacetate is also investigated and shown to display the same behavior, with an A-1 mechanism involving an intermediate CH3COOCH2+ becoming important at about 75% H2SO4. The relative AA1-1 reactivities for acetates ROAc, R = CH3OCH2, tert-butyl, C6H5OCH2, C6H5CH2, 4-NO2C6H4OCH2, CH3COOCH2, isopropyl, are 6 × 103, 5 × 102, 1, 7 × 10−2, 4 × l0−2, 1.1 × 10−2, 1.3 × 10−4 respectively.

Orientation in the Wallach Rearrangement for the Naphthyl Azoxy Series

1974 ◽  
Vol 52 (4) ◽  
pp. 623-629 ◽  
Author(s):  
Allan Dolenko ◽  
Erwin Buncel
Keyword(s):  
Sulfuric Acid ◽  
Acid Solutions ◽  
Benzene Rings ◽  
Acid Catalyzed ◽  
Sulfuric Acid Solutions

The acid-catalyzed Wallach rearrangement of azoxybenzenes has been extended to the naphthyl azoxy series in order to evaluate the effect of annelation of benzene rings on the course of rearrangement. The six known azoxy derivatives containing the α-naphthyl, β-naphthyl, and phenyl moieties, in various combinations, have been examined with respect to product orientation in moderately strong sulfuric acid solutions. The course of rearrangement (eqs. 2–6) is discussed on the basis of current mechanisms.

Mechanistic variation in the reactions of substituted acetamides in aqueous sulfuric acid

1984 ◽  
Vol 62 (11) ◽  
pp. 2401-2414 ◽  
Author(s):  
Linda M. Druet ◽  
Keith Yates
Keyword(s):  
Sulfuric Acid ◽  
Water Molecules ◽  
Acid Solutions ◽  
Reaction Products ◽  
Aqueous Sulfuric Acid ◽  
Rate Determining Step ◽  
Wide Range ◽  
Acid Catalyzed ◽  
Catalyzed Reactions ◽  
Sulfuric Acid Solutions

The acid-catalyzed reactions of acetamide 1, N-tert-butylacetamide 2, and several p-substituted N-benzylacetamides (3 = H, 4 = CH3, 5 = OCH3, 6 = Cl, 7 = NO2) have been studied as a function of acidity and temperature over a wide range of aqueous sulfuric acid solutions (0–91%). Analysis of the reaction products and rate–acidity profiles revealed that four different mechanisms are operative over different acidity regions depending on the structure of the substrate. These are: two A-2 hydrolysis mechanisms with N-acyl fission of the substrate (with participation of one or several water molecules in the rate-determining step); A-1 hydrolysis with N-alkyl fission; and sulfonation, followed by hydrolysis. These conclusions are supported by three complementary and detailed kinetic treatments based on the hydration parameter, transition state activity coefficient, and excess acidity approaches. The acidity domains of each mechanism have been established for each substrate. The mechanistic conclusions are fully supported by the different values of ΔH‡ and ΔS‡ obtained in different regions of acidity.

Protonation of conjugated carbonyl groups in sulfuric acid solutions. II. Protonation and basicity of α,β-unsaturated alicyclic ketones

1969 ◽  
Vol 47 (12) ◽  
pp. 2263-2270 ◽  
Author(s):  
R. I. Zalewski ◽  
G. E. Dunn
Keyword(s):  
Sulfuric Acid ◽  
Substituent Effects ◽  
Acidity Function ◽  
Acid Solutions ◽  
Carbonyl Groups ◽  
Resonance Effects ◽  
Unit Slope ◽  
Straight Lines ◽  
Sulfuric Acid Solutions

The protonation of 14 α,β-unsaturated alicyclic ketones, B, by sulfuric acid leads to values of log [B]/[BH+] which, when plotted against the amide acidity function, HA, give straight lines of unit slope. The [Formula: see text] values thus obtained show substituent effects which are additive and can be interpreted in terms of polar and resonance effects.

Protection features of chromium-nickel steel in sulfuric acid solutions by triazole derivative

2019 ◽  
pp. 15-21
Author(s):  
Ya.G. Avdeev ◽  
◽  
Yu.B. Makarychev ◽  
D.S. Kuznetsov ◽  
L.P. Kazanskii ◽  
...  
Keyword(s):  
Sulfuric Acid ◽  
Nickel Steel ◽  
Acid Solutions ◽  
Triazole Derivative ◽  
Sulfuric Acid Solutions

Rheological Characterization of Sulfuric Acid Solutions of Poly(p-phenyleneterephthalamide)

1987 ◽  
Vol 2 (1) ◽  
pp. 28-32 ◽  
Author(s):  
B. C. Kim ◽  
S. S. Hwang ◽  
K. U. Kim
Keyword(s):  
Sulfuric Acid ◽  
Acid Solutions ◽  
Rheological Characterization ◽  
Sulfuric Acid Solutions
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