The cyclization of 2-substituted imidazolines in sulfuric acid

1994 ◽  
Vol 72 (9) ◽  
pp. 1910-1914 ◽  
Author(s):  
Robin A. Cox ◽  
David B. Moore ◽  
Robert S. McDonald
Keyword(s):  
Sulfuric Acid ◽  
Water Molecule ◽  
Kinetic Analysis ◽  
Ring Closure ◽  
Base Catalyst ◽  
Aqueous Sulfuric Acid ◽  
Medium Acidity

A study of the rates of the cyclizations 1 → 3 and 2 → 4 as a function of medium acidity and temperature in aqueous sulfuric acid has been performed. The latter reaction is five times faster at all acidities. An excess acidity kinetic analysis reveals the probable involvement of a water molecule in the reaction in both cases. Mechanistic possibilities suggested by the observations are discussed; it is proposed that the water molecule acts as a base catalyst during the rate-determining ring closure.

The decomposition of aliphatic N-nitro amines in aqueous sulfuric acid. Bisulfate as a nucleophile

1996 ◽  
Vol 74 (10) ◽  
pp. 1774-1778 ◽  
Author(s):  
Robin A. Cox
Keyword(s):  
Sulfuric Acid ◽  
Water Molecule ◽  
Rate Constants ◽  
Activation Parameters ◽  
Standard State ◽  
Aqueous Sulfuric Acid ◽  
Alkyl Groups ◽  
Different Temperatures ◽  
State Rate ◽  
Acid Catalyzed

In aqueous sulfuric acid, aliphatic N-nitro amines decompose to N2O and alcohols. An excess acidity analysis of the observed rate constants for the reaction shows that free carbocations are not formed. The reaction is an acid-catalyzed SN2 displacement from the protonated aci-nitro tautomer, the nucleophile being a water molecule at acidities below 82–85% H2SO4, and a bisulfate ion at higher acidities. Bisulfate is the poorer nucleophile by a factor of about 1000. Twelve compounds were studied, of which results obtained for nine at several different temperatures enabled calculation of activation parameters for both nucleophiles. The reaction appears to be mainly enthalpy controlled. The intercept standard-state rate constants are well correlated by the σ* values for the alkyl groups; the slopes are negative, with a more negative value for the slower bisulfate reaction. Interestingly the m≠m* slopes also correlate with σ*, although the scatter is bad. Key words: N-nitro amines, excess acidity, bisulfate, nucleophiles, acid-catalyzed, kinetics.

scholarly journals RATE ENHANCEMENTS DUE TO AQUEOUS SULFURIC ACID IN Mn (III) OXIDATION OF CERTAIN PURINE ALKALOIDS - KINETIC ANALYSIS OF ACIDITY FUNCTIONS

2021 ◽  
Vol 14 (03) ◽  
Author(s):  
A. Ramakrishna Reddy ◽  
J. Prasad ◽  
M. Bhooshan ◽  
K. C. Rajanna ◽  
A. Panasa Reddy ◽  
...  
Keyword(s):  
Sulfuric Acid ◽  
Kinetic Analysis ◽  
Aqueous Sulfuric Acid ◽  
Purine Alkaloids ◽  
Acidity Functions

Hydrolysis mechanisms for acylhydrazines in aqueous sulfuric acid, determined using the excess acidity method

1984 ◽  
Vol 62 (8) ◽  
pp. 1613-1617 ◽  
Author(s):  
Robin A. Cox ◽  
Keith Yates
Keyword(s):  
Sulfuric Acid ◽  
Water Molecule ◽  
Proton Transfer ◽  
Medium Composition ◽  
Hydrolysis Rate ◽  
Bond Rupture ◽  
Rate Data ◽  
Dilute Acid ◽  
Aqueous Sulfuric Acid ◽  
Rate Determining Step

The excess acidity method has been applied to hydrolysis rate data for some acyl- and benzoylhydrazines, obtained as a function of medium composition in aqueous sulfuric acid mixtures. Two hydrolysis mechanisms are indicated, both involving a second proton transfer to monoprotonated substrate. In the first mechanism this transfer is to oxygen, which is the rate-determining step in dilute acid, followed by attack of a water molecule in an A-2 hydrolysis, which is rate determining in more concentrated acid. Bisulfate ion becomes the nucleophile at high acidity. The second mechanism, found at higher acid concentrations, involves rate-determining nitrogen protonation, probably concerted with C—N bond rupture, to give an acylium ion, for those substrates capable of forming one.

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

Reduction of bromine(V) by cerium(III), manganese(II), and neptunium(V) in aqueous sulfuric acid

1971 ◽  
Vol 93 (26) ◽  
pp. 7315-7315 ◽  
Author(s):  
Richard C. Thompson
Keyword(s):  
Sulfuric Acid ◽  
Aqueous Sulfuric Acid

scholarly journals Synthesis of Monodisperse Fine TiO2 Particles by Aqueous Sulfuric Acid Droplets Solubilized by Reversed Micelles

1998 ◽  
Vol 71 (4) ◽  
pp. 225-231
Author(s):  
Daisuke KANEKO ◽  
Takeshi KAWAI ◽  
Kijiro KON-NO
Keyword(s):  
Sulfuric Acid ◽  
Reversed Micelles ◽  
Tio2 Particles ◽  
Aqueous Sulfuric Acid ◽  
Fine Tio2
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