ISOTOPE RATE EFFECTS IN THE ENOLIZATION OF OXALACETIC ACID

1962 ◽  
Vol 40 (7) ◽  
pp. 1280-1284 ◽  
Author(s):  
George W. Kosicki
Keyword(s):  
Direct Evidence ◽  
Aqueous System ◽  
Enol Form ◽  
Rate Effect ◽  
Keto Form ◽  
Oxalacetic Acid ◽  
Rate Determining Step ◽  
Rate Effects ◽  
Acid Catalyzed ◽  
Catalyzed Reactions

Acid-catalyzed enolization of oxalacetic acid in H2O and D2O gives rise to a constant isotope rate effect [Formula: see text] of 2.4 over the pH (pD) range of 5.5 to 7.5. Base-catalyzed enolization of oxalacetic acid in H2O and D2O gives rise to a constant isotope rate effect [Formula: see text] of 4.5 over the pH (pD) range of 7.0 to 8.0. The percentage of enol form of oxalacetic acid was calculated to be 15.3% at pH 8.0, using the absorption of the enol form in ether at 255 mμ and the absorption of the keto form at pH 0.5 in an aqueous system. The spectrophotometric measurement of the isotope rate effect involved in the enolization of oxalacetic acid gives direct evidence for the rate-determining step in both the acid- and the base-catalyzed reactions without subsequent reactions.

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.

Photoinduced rearrangement of hydroxymethylisoxazolines, a route to enaminoaldehydes

1986 ◽  
Vol 51 (10) ◽  
pp. 2167-2180 ◽  
Author(s):  
Lubor Fišera ◽  
Nadezhda D. Kozhina ◽  
Peter Oravec ◽  
Hans-Joachim Timpe ◽  
Ladislav Štibrányi ◽  
...  
Keyword(s):  
Thionyl Chloride ◽  
Quantum Yields ◽  
Acid Catalyzed ◽  
Catalyzed Reactions ◽  
Photoinduced Rearrangement ◽  
Condensed Heterocycles

3-Aryl-4-R-carbamoyl-5-hydroxymethylisoxazolines (IV) were synthesized by allowing R-NH2 amines with R = H, CH3, C3H7, C6H5C2H5, and NH2 to act on 3-(X-phenyl)-4-oxo-3a,4,6,6a-tetrahydrofuro[3,4-d]isoxazoles (III) with X = H, 4-CH3, 4-OCH3, 2-OCH3, 4-Cl, 2-Cl, 4-F, 2-F, 4-Br, 4-NO2, and 3-NO2. Exposed to radiation, the substances IV give Z-2-hydroxymethylamino-2-aryl-1-formylacrylamides (V) in good yields. The 4-Cl and 4-F substituted Z-derivatives V isomerize irreversibly to the E-derivatives VI if allowed to stand in solvent; the remaining derivatives V are stable. The quantum yields of the photoreaction are from 0.012 to 0.106 in dependence on the substituent X. In all cases where the compounds IV were used for the preparation of condensed heterocycles in conditions of acid-catalyzed reactions, lactones III were preferentially formed; the action of thionyl chloride on IV results in the formation of chloromethyl derivatives VIII, which do not undergo further cyclization.

Synthetic Scope of Brønsted Acid-Catalyzed Reactions of Carbonyl Compounds and Ethyl Diazoacetate

2021 ◽  
Author(s):  
Mizzanoor Rahaman ◽  
M. Shahnawaz Ali ◽  
Khorshada Jahan ◽  
Damon Hinz ◽  
Jawad Bin Belayet ◽  
...  
Keyword(s):  
Carbonyl Compounds ◽  
Bronsted Acid ◽  
Brønsted Acid ◽  
Ethyl Diazoacetate ◽  
Brönsted Acid ◽  
Acid Catalyzed ◽  
Catalyzed Reactions

Kinetic modelling of reactions for the synthesis of 2-methyl-5-ethyl pyridine

2021 ◽  
Author(s):  
Emanuele Moioli ◽  
Leo Schmid ◽  
Peter Wasserscheid ◽  
Hannsjoerg Freund
Keyword(s):  
Kinetic Modelling ◽  
Acid Catalyst ◽  
Acid Catalyzed ◽  
Catalyzed Reactions ◽  
Kinetics Of

The kinetics of the acid catalyzed reactions of acetaldehyde ammonia trimer (AAT) and paraldehyde (para) to 2-methyl-5-ethyl pyridine (MEP) in the presence of an acid catalyst were investigated systematically. A...

ChemInform Abstract: ACID-CATALYZED REACTIONS OF CYCLOBUTANONES. III. FORMATION OF SUBSTITUTED 2-TETRALONES FROM α-PHENYLCYCLOBUTANONES

1978 ◽  
Vol 9 (20) ◽  
Author(s):  
V. P. ABEGG ◽  
A. C. HOPKINSON ◽  
E. LEE-RUFF
Keyword(s):  
Acid Catalyzed ◽  
Catalyzed Reactions

LITHIUM CHLORIDE CATALYZED DECARBOXYLATION OF OXALACETIC ACID IN ETHANOL

1964 ◽  
Vol 42 (12) ◽  
pp. 2806-2810 ◽  
Author(s):  
G. W. Kosicki ◽  
S. N. Lipovac ◽  
R. G. Annett
Keyword(s):  
Hydrogen Chloride ◽  
Lithium Chloride ◽  
Pyruvic Acid ◽  
Metal Salt ◽  
Enol Form ◽  
Absorption Peak ◽  
Oxalacetic Acid ◽  
Monovalent Metal

The monovalent metal salt lithium chloride promotes the decarboxylation of oxalacetic acid in ethanol. The absorption peak which appears at 230 mμ during the reaction is interpreted to be the enol form of pyruvic acid. Hydrogen chloride has a similar effect on the decarboxylation.

ChemInform Abstract: Intramolecular Acid-Catalyzed Reactions of o-Carbomethoxy-ω-diazoacetophenones.

ChemInform ◽  
1987 ◽  
Vol 18 (47) ◽  
Author(s):  
S. V. CHAPYSHEV ◽  
L. I. KIRKOVSKII ◽  
V. G. KARTSEV
Keyword(s):  
Acid Catalyzed ◽  
Catalyzed Reactions
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