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.

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.

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.

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.

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.

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.

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

Electrochemistry of Gold in Aqueous Sulfuric Acid Solutions under Neural Stimulation Conditions

2005 ◽  
Vol 152 (7) ◽  
pp. E212 ◽  
Author(s):  
Daniel R. Merrill ◽  
Ionel C. Stefan ◽  
Daniel A. Scherson ◽  
J. Thomas Mortimer
Keyword(s):  
Sulfuric Acid ◽  
Neural Stimulation ◽  
Acid Solutions ◽  
Aqueous Sulfuric Acid ◽  
Sulfuric Acid Solutions
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