16885-78-2Relevant academic research and scientific papers
Nucleophilic displacement at the benzoyl centre: A study of the change in geometry at the carbonyl carbon atom
Colthurst, Matthew J.,Williams, Andrew
, p. 1493 - 1497 (2007/10/03)
The second-order rate constants for the reaction between hydroxide ion and phenoxide ion with 4-nitrophenyl esters of substituted benzoic acids in 10% acetonitrile-water (v/v) solution obey Hammett σ correlations. The values of the Hammett ρ of 1.67 (κArO) and 2.14 (κOH) are consistent with a large change in hybridization at the central carbon by comparison with the ρ value for a standard reaction where a full sp2 to sp3 change occurs. The transition state for the concerted reaction thus has a substantially tetrahedral geometry. The observation of the anti-Hammond effect whereby the ρ value for the hydroxide ion exceeds that of the less reactive phenoxide ion is consistent with a concerted, ANDN, mechanism for these reactions. A stepwise mechanism, AN + DN, is unlikely to yield a measurable break in the Hammett correlation for a change in the benzoyl substituent if the partitioning of the putative tetrahedral intermediate involves forward and reverse reactions with Hammett correlations possessing similar ρ values.
Dissociation Constants of Weak Organic Acids in Protic Solvents Obtained from Their First Hyperpolarizabilities in Solution
Ray, Paresh Chandra,Das, Puspendu Kumar
, p. 17891 - 17895 (2007/10/03)
The first hyperpolarizabilities (β) of some weak aromatic organic acids have been measured in protic solvents by the hyper-Rayleigh scattering (HRS) technique at low concentrations.The measured hyperpolarizability (βm) varies between the two extreme limits: the hyperpolarizability of the acid form (βHA) at the lower side and that of the basic form (βA-) at the higher side.The degree of dissociation (α) of the acid in a solvent is related to the measured hyperpolarizability, βm, by the following relationship: βm2 = (1 - α)βHA2 + αβA-2.The calculated β's including solvent effects in terms of an Onsager field do not reproduce the experimentally measured hyperpolarizabilities.Other solvent-induced effects like hydrogen bonding and van der Waals interactions seem to influence the first hyperpolarizability and, thus, indirectly the extent of dissociation of these weak acids in these protic solvents.
Cationic Micellar Effect on the Kinetics of the Protolysis of Aromatic Carboxylic Acids studied by the Ultrasonic Absorption Method
Isoda, Teruyo,Yamasaki, Miyuki,Yano, Hiroshige,Sano, Takayuki,Harada, Shoji
, p. 869 - 874 (2007/10/02)
The protolysis of carboxylic acids has been kinetically studied by the ultrasonic absorption method in the presence of tetradecyltrimethylammonium bromide (TTAB) micelles in aqueous solution.The carboxylic acids studied were classified into two categories, one capable of formation of intramolecular hydrogen bond, namely the salicylic acid derivatives (SAD) and the other which cannot form the bond, namely the benzoic acid derivatives (BAD).The rate constant (γ2kf, kb), the apparent dissociation constant (Ka), and the volume change of the reaction (ΔV) were obtained.Different Ka dependences of the rate constants observed for SAD and BAD are discussed in relation to the effect of intramolecular hydrogen bond. pKa dependences were also observed for ΔV of SAD and BAD.These dependences are larger than those in aqueous solution.This result was attributed to the change of arrangement of water molecules around the solute in micellar solution and aqueous solution.
