Hemiacetals of acetophenone. Aromatic substituent effects in the H+- and general-base-catalysed decomposition in aqueous solution

1994 ◽  
pp. 2199-2206 ◽  
Author(s):  
Robert A. McClelland ◽  
Karen M. Engell ◽  
Truels S. Larsen ◽  
Poul E. Sørensen
Keyword(s):  
Aqueous Solution ◽  
Substituent Effects ◽  
Aromatic Substituent ◽  
General Base

Micellar catalysis of organic reactions. VIII. Kinetic studies of the hydrolysis of 2-acetyloxybenzoic acid (aspirin) in the presence of micelles

1982 ◽  
Vol 35 (7) ◽  
pp. 1357 ◽  
Author(s):  
TJ Broxton
Keyword(s):  
Aqueous Solution ◽  
Cetyltrimethylammonium Bromide ◽  
Cetylpyridinium Chloride ◽  
Kinetic Studies ◽  
Base Catalysis ◽  
Plateau Region ◽  
General Base ◽  
Mechanism Of Hydrolysis ◽  
Ph Range ◽  
Hydrolysis Of

The hydrolysis of 2-acetyloxybenzoic acid in the pH range 6-12 has been studied in the presence of micelles of cetyltrimethylammonium bromide (ctab) and cetylpyridinium chloride (cpc). In the plateau region (pH 6-8) the hydrolysis is inhibited by the presence of micelles, while in the region where the normal BAC2 hydrolysis (pH > 9) occurs the reaction is catalysed by micelles of ctab and cpc. The mechanism of hydrolysis in the plateau region is shown to involve general base catalysis by the adjacent ionized carboxy group both in the presence and absence of micelles. This reaction is inhibited in the presence of micelles because the substrate molecules are solubilized into the micelle and water is less available in this environment than in normal aqueous solution.

Substituent effects on the binding of phenols to cyclodextrins in aqueous solution

1989 ◽  
Vol 93 (18) ◽  
pp. 6863-6867 ◽  
Author(s):  
Gary L. Bertrand ◽  
James R. Faulkner ◽  
Soon M. Han ◽  
Daniel W. Armstrong
Keyword(s):  
Aqueous Solution ◽  
Substituent Effects

scholarly journals Ring Structure and Aromatic Substituent Effects on the pKa of the Benzoxaborole Pharmacophore

2011 ◽  
Vol 3 (1) ◽  
pp. 48-52 ◽  
Author(s):  
John W. Tomsho ◽  
Arnab Pal ◽  
Dennis G. Hall ◽  
Stephen J. Benkovic
Keyword(s):  
Substituent Effects ◽  
Ring Structure ◽  
Aromatic Substituent

Substituent effects in naphthalene. II. The strengths of the 4, 5, 6, 7, and 8-substituted 2-naphthoic acids

1965 ◽  
Vol 18 (9) ◽  
pp. 1365 ◽  
Author(s):  
PR Wells ◽  
W Adcock
Keyword(s):  
Electrostatic Interactions ◽  
Aqueous Ethanol ◽  
Substituent Effects ◽  
Simple Expression ◽  
Dipole Orientation ◽  
Aromatic Substituent ◽  
Resonance Effects ◽  
Naphthoic Acid ◽  
Inductive Effects ◽  
Substituted 1

The apparent pKa values of 44 substituted 2-naphthoic acids, six substituted 1-naphthoic acids, and the unsubstituted naphthoic acids have been determined for 50% v/v aqueous ethanol at 25�. The ΔpK values are examined in terms of Dewar and Grisdale's simple expression for aromatic substituent effects. This expression proves to be fairly satisfactory, but takes no account of substituent dipole orientation, secondary resonance effects, nor π-inductive effects. A survey of the naphthoic acid strengths demonstrates the importance of these factors. In particular, unambiguous evidence for the important role played by direct electrostatic interactions is obtained.

Kinetics and mechanism of the bromination of phenols in aqueous solution. Evidence of general base catalysis of bromine attack

1990 ◽  
Vol 68 (10) ◽  
pp. 1769-1773 ◽  
Author(s):  
Oswald S. Tee ◽  
N. Rani Iyengar
Keyword(s):  
Aqueous Solution ◽  
Kinetics And Mechanism ◽  
Base Catalysis ◽  
Hydroxyl Group ◽  
Molecular Bromine ◽  
Electrophilic Attack ◽  
General Base ◽  
Carboxylate Anions

The reactions of bromine with phenol, 4-bromophenol, and 4-methylphenol (p-cresol) in aqueous solution are catalyzed by carboxylate anions, confirming the suggestions of earlier work. The results are consistent with deprotonation of the phenol hydroxyl group by a general base occurring at more or less the same time as electrophilic attack by molecular bromine. Possible origins of the general base catalysis are discussed. Combined with earlier results, the present findings suggest that a protonated cyclohexadienone is not a mandatory intermediate in phenol bromination; it can be avoided in both the formation of and enolization of the cyclohexadienone intermediate by general catalysis. Keywords: bromination, phenol, mechanism, catalysis, kinetics.

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