44. Chemical constitution and the dissociation constants of monocarboxylic acids. Part XVI. Some acylbenzoic acids

Abstract

The monoacetylbenzoic acids display the order of strengths p-> m-> o-> H (in water a t 2 6 ' ) and the fact that the o-isomer is only a little stronger than the parent benzoic acid is interpreted in terms of the view that the acetyl group is less strongly conjugated with the benzene ring than is the carboxyl group. The greater bulks of benzoyl and toluoyl groups, and their stronger conjugative capacities, account for the relatively large enhancements in strength exhibited when these groups enter the ortho-position.THE dissociation constants of five acylbenzoic acids have been determined in water at 25" by the conductivity method (Table 1). The expectation that the groups Ac, Bz, and P-C,H,Me*CO would enhance the strength of benzoic acid when substituted in the benzene

Ring–chain tautomerism and protolytic equilibria of 3-hydroxy-3-phosphonoisobenzofuranone studied by 1H, 13C and 31P NMR-controlled titrations

“…The parent benzoylphosphonic acid was characterized by pK 1 = 0.39 and pK 2 = 5.60 20 while for benzoic acid pK = 4.20 21 was found. Early investigations on ortho-formyl-, acetyland benzoyl-substituted benzoic acids in equilibrium with corresponding ring-forms yielded pK values of 4.56, 4.14 22 and 3.53, 23 respectively. Hence, it is tempting to assign the three pK values found for the title compound 6 to three elementary steps:…”

Reactions of carbonyl compounds in basic solutions. Part 33.1 Effect of 2-trichloro- and tribromoacetyl substituents on the alkaline hydrolysis of methyl benzoate, as well as the hydrolysis of the corresponding benzoate anions and ionisation/ring–chain tautomerism of the corresponding acids

“…In Table 4 are shown the pK a values of the acids, together with estimates of pK a values of the chain tautomers. The latter are based on the pK a value of 2-benzoylbenzoic acid in water (3.53 5 ), 17 together with the polar substituent effects of Ph, CBr 3 and CCl 3 14 and their transmission. 18 The K e values for 2-tribromo-and trichloroacetylbenzoic acids in water are shown in Table 4 as 100 and 78, respectively.…”

Selective Oxidation of Acetophenones Bearing Various Functional Groups to Benzoic Acid Derivatives with Molecular Oxygen

“…For instance, 2b is prepared from acetophenone by nitration, reduction, diazotation, reaction with cuprous cyanide and hydrolysis. [9] In addition, Camps reported a method for 2b based on the Claisen condensation of isophthalic acid with methylene carboxylic esters. [13] The oxidation of 4-ethylacetophenone (1e) and 4-isopropylacetophenone (1f) gave rise to 1,4-diacetylbenzene (5) in 87% and 45% yields, respectively, under optimized reaction conditions (entries 5 and 6).…”

“…In particular, a method for the preparation of acetylbenzoic acids is important, since the preparation of these compounds is not an easy task. [9] In this paper, we wish to report a new selective method for the synthesis of benzoic acid derivatives by the aerobic oxidation of aromatic compounds bearing an acyl group by a catalytic system consisting of MnA C H T U N G T R E N N U N G (OAc) 2 …”