Kinetics and mechanism of N–H and C–H exchange in pyrrole and indole. Part II. General acid catalysed exchange in aqueous acetonitrile

1976 ◽  
pp. 388-392 ◽  
Author(s):  
David M. Muir ◽  
Mark C. Whiting
Keyword(s):  
Kinetics And Mechanism ◽  
Aqueous Acetonitrile ◽  
General Acid

The kinetics and mechanism of the oxidation of mercaptoethanol by riboflavin

1977 ◽  
Vol 30 (6) ◽  
pp. 1387 ◽  
Author(s):  
JW Holden ◽  
L Main
Keyword(s):  
Kinetic Study ◽  
Acid Catalysis ◽  
Kinetics And Mechanism ◽  
Alternative Mechanism ◽  
Semiquinone Radical ◽  
Radical Intermediate ◽  
General Acid ◽  
Elimination Mechanism ◽  
Ph Range ◽  
Kinetic Form

Kinetic study of the oxidation of mercaptoethanol (RSH) by riboflavin (FlH) over the pH range 8.5-10.5 establishes that the rate is given by the term 0.036[FlH][RSH][RS-]]2 mol-2 s-1, there being no buffer catalysis. Any reactivity of the N 3-ionized riboflavin species (Fl-) is sufficiently low to be kinetically undetected. The kinetic form and lack of general acid catalysis are consistent with a nucleophilic (thiolate) 4a-addition-elimination mechanism previously proposed, but a possible alternative mechanism involving a flavin semiquinone (radical) intermediate is suggested.

Kinetics and mechanism of solvolysis of N-aryl sulfuric diamides

1990 ◽  
Vol 55 (1) ◽  
pp. 202-222 ◽  
Author(s):  
Jaromír Kaválek ◽  
Ulrika Králíková ◽  
Vladimír Macháček ◽  
Miloš Sedlák ◽  
Vojeslav Štěrba
Keyword(s):  
Acid Catalysis ◽  
Catalytic Effect ◽  
Kinetics And Mechanism ◽  
Base Catalysis ◽  
Reactive Intermediate ◽  
Hydrolysis Kinetics ◽  
General Acid ◽  
Acid And Base ◽  
Elimination Mechanism ◽  
Acid And Base Catalysis

The methanolysis and hydrolysis kinetics have been studied with the following sulfuric diamide derivatives: N-methyl-N-phenyl- (IIIa), N-methyl-N-(4-methoxycarbonylphenyl)- (IIIb), N-(4-methoxycarbonylphenyl)- (IIIc), N-methyl-N-(2-methoxycarbonylphenyl)- (IIId), N-(2-methoxycarbonylphenyl)- (IIIe), and N-methyl-N-(2,4-dibromophenyl)- (IIIf). The solvolyses of the neutral substrates IIIa and IIIb proceed by the addition-elimination mechanism. In the presence of the solvent lyate ions the solvolyses go by the E1cb mechanism. The solvolyses of the conjugated bases of compounds IIIa and IIIb are subject to general acid catalysis, the effects of the ring substituents being opposite to those in the addition-elimination mechanism. The solvolyses of compounds IIId and IIIf exhibit a distinct catalytic effect of neighbouring group; the reaction goes via a reactive intermediate, the transformation of the intermediate into the solvolysis product being subject to general acid and base catalysis.

Sign in / Sign up

Export Citation Format

Share Document