Mechanism of Sulfonation of 4-Hydroxyazobenzene

1971 ◽  
Vol 49 (1) ◽  
pp. 152-156 ◽  
Author(s):  
E. Buncel ◽  
W. M. J. Strachan ◽  
H. Cerfontain
Keyword(s):  
Sulfuric Acid ◽  
Complex Formation ◽  
Sulfonic Acid ◽  
Acid Media ◽  
Proton Abstraction ◽  
Rate Determining Step ◽  
Concentrated Sulfuric Acid

The mechanism of sulfonation of 4-hydroxyazobenzene and of 4-hydroxyazobenzene-4′-sulfonic acid in concentrated sulfuric acid media is examined through rate correlations and comparison is drawn with sulfonation of alkyl- and halogenobenzenes by means of [Formula: see text] plots. It is concluded that several mechanisms are operative in the hydroxyazobenzene system and that the curvature of the plot is the result of a change in rate-determining step from σ-complex formation to proton abstraction.

Study of vanadium(IV) species and corresponding electrochemical performance in concentrated sulfuric acid media

2011 ◽  
Vol 56 (27) ◽  
pp. 10197-10203 ◽  
Author(s):  
Xuewen Wu ◽  
Jinjin Wang ◽  
Suqin Liu ◽  
Xiongwei Wu ◽  
Sha Li
Keyword(s):  
Sulfuric Acid ◽  
Electrochemical Performance ◽  
Acid Media ◽  
Concentrated Sulfuric Acid

Methylation of polymethylbenzenesulfonic acids by hexamethylbenzene and pentamethylbenzenesulfonic acid in concentrated sulfuric acid

1988 ◽  
Vol 66 (1) ◽  
pp. 162-167 ◽  
Author(s):  
Hans Cerfontain ◽  
Ankie Koeberg-Telder
Keyword(s):  
Sulfuric Acid ◽  
Sulfonic Acid ◽  
Sulfonic Acids ◽  
Substrate Reactivity ◽  
Concentrated Sulfuric Acid

The methylation of a series of polymethylbenzenes (PoMB's) or their sulfonic acids by added hexamethylbenzene (HMB) and pentamethylbenzene-1-sulfonic acid (PeMB-1-S) as reagents in 95.5 and 98.4% H2SO4 as solvent has been studied under homogeneous conditions. HMB effects methylation of 2,4,6-trimethylbenzene-1-sulfonic acid (2,4,6-TrMB-1-S), 2,3,4,6-tetramethylbenzene-1-sulfonic acid (2,3,4,6-TeMB-1-S), and 2,3,5,6-TeMB-1-S, but not of the sulfonic acids of 1,3-dimethylbenzene (1,3-DMB), 1,2,3-TrMB, 1,2,4-TrMB, and 1,2,3,4-TeMB. PeMB-1-S is less reactive as methylating reagent than HMB. The observed substrate reactivity towards methylation by HMB was observed to decrease in the order [Formula: see text], and towards methylation by PeMB-1-S to decrease in the order [Formula: see text]. On the basis of a comparison of these orders of substrate reactivities with those predicted for the series of the PoMB-1-sulfonates and the corresponding PoMB's, it is concluded that the substrate species undergoing methylation are the PoMB's and not the corresponding sulfonates.

The excess acidity method. The basicities, and rates and mechanisms of enolization, of some acetophenones and acetone, in moderately concentrated sulfuric acid

1979 ◽  
Vol 57 (22) ◽  
pp. 2952-2959 ◽  
Author(s):  
Robin A. Cox ◽  
Clinton R. Smith ◽  
Keith Yates
Keyword(s):  
Sulfuric Acid ◽  
Function Method ◽  
Water Molecules ◽  
Acid Solutions ◽  
Linear Free Energy ◽  
Rate Determining Step ◽  
Energy Relationships ◽  
Concentrated Sulfuric Acid ◽  
Sulfuric Acid Solutions ◽  
Medium Acidity

The X-function method has been used to evaluate the basicities of six nuclear-substituted acetophenones and acetone, using a combination of new measurements and literature data; the protonation [Formula: see text] of acetone was found to be −5.37. The same method, which involves the excess medium acidity, when used to analyze the enolization rate constants obtained from the measured bromination rates, shows that most of the acetophenones enolize by an A-2 process involving two water molecules in the rate-determining step. Observed linear free energy relationships for the basicities and the enolization rates imply a relatively early transition state for the enolization. Acetone was found to enolize by a similar mechanism in sulfuric acid solutions more dilute than 81% w/w, but at higher acidities bisulfate ion was the preferred base. The mechanistic behaviour of 4-nitroacetophenone was found to be different, not A-2 but either A-1 or A-SE2.

Meso and β-pyrrole sulfonated porphyrins obtained by sulfonation of 5,15-bis(phenyl)porphyrin

2000 ◽  
Vol 04 (05) ◽  
pp. 564-568 ◽  
Author(s):  
HECTOR GARCIA-ORTEGA ◽  
JOSEP M. RIBO
Keyword(s):  
Sulfuric Acid ◽  
Sodium Salt ◽  
Good Yield ◽  
Sulfonic Acid ◽  
Disulfonic Acid ◽  
Acid Mixture ◽  
Sodium Salts ◽  
Concentrated Sulfuric Acid ◽  
Trisodium Salt

The sulfonation of 5,15-bis(phenyl)porphyrin (DPP) in concentrated sulfuric acid results in substitution on the β-pyrrolic positions and the expected sulfonation on the para positions of the phenyl substituents. The sodium salt of 5,15-bis(4-sulfonatophenyl)porphyrin-2-sulfonic acid ( S 3 DPP ) was prepared in good yield, the sodium salts of 5,15-bis(4-sulfonatophenyl)porphyrin ( S 2 A DPP ), 5-phenyl-15-(4-sulfonatophenyl)porphyrin-2-sulfonic acid ( S 2 B DPP ) and 15-phenyl-5-(4-sulfonatophenyl)porphyrin ( S 1 A DPP ) were isolated, and 5,15-bis(phenyl)porphyrin-2-sulfonic acid ( S 1 B DPP ) was detected in a mixture with S 1 A DPP . The β-pyrrole sulfonato substituents are stable and their potential synthetic use is shown by the preparation of the trisodium salt of 10-bromo-5,15-bis(4-sulfonatophenyl)porphyrin-2-sulfonic acid ( BrS 3 DPP ) by NBS bromination of S 3 DPP . In a methanol/sulfuric acid mixture the sulfonation occurs on the meso positions, and the tetrasodium salt of 10,20-bis (4-sulfonatophenyl)porphyrin-5,15-disulfonic acid ( S 4 DPP ) was obtained.

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