Topic
Carboxylic acid
About: Carboxylic acid is a research topic. Over the lifetime, 48544 publications have been published within this topic receiving 605696 citations.
Papers published on a yearly basis
Papers
More filters
Abstract: Extraction mechanism strongly depends on the acid-base properties of the extractant as well as on those of the extracted acid. For amines of basicity similar to that of the anion of the extracted acid, or higher, extraction is governed by ion-pair formation. H-bonding of undissociated acid becomes important only for extraction of weak acids by weak bases. Extraction mechanism determines the effect of various parameters. Thus the degree of extraction is most sensitive to pH at about the pK{sub a} of the amine for extraction through ion-pair formation. Extraction by H-bonding, however, is most sensitive at about the pK{sub a} of the acid. Polar and protic diluents enhance extraction through ion-pair formation, but may have no effect on H-bonding or even hinder it. Extraction through ion-pair formation prefers stronger acids at low pH while H-bonding extracts weaker acids more efficiently. Clarification of the extraction mechanism and its dependence on extracted acid properties and on the pH provide for designing extractants of high efficiency and selectivity.
196 citations
TL;DR: The extremely chemically resistant component of the cell wall of spores, pollens, and some microorganisms, sporopollenin, is generally accepted to be derived from carotenoids orCarotenoid esters, but (13)C NMR analyses of sporipollenin from several sources shows that this widely held view is incorrect.
Abstract: The extremely chemically resistant component of the cell wall of spores, pollens, and some microorganisms, sporopollenin, is generally accepted to be derived from carotenoids or carotenoid esters. However, we report here that 13C NMR analyses of sporopollenin from several sources shows that this widely held view is incorrect, with one possible exception. Sporopollenin is not a unique substance but rather a series of related biopolymers derived from largely saturated precursors such as fatty acids. The biopolymers contain widely varying amounts of oxygen in the form of ether, hydroxyl, carboxylic acid, ester, and ketone groups.
196 citations
TL;DR: In this article, electron paramagnetic resonance (EPR) spectroscopy and enantioselectivity studies were performed to identify the active oxygen-transferring species of the above systems, which can be identified as structurally similar oxometal(V) species of [((S,S)-pdp)MV═O(OCOR)]2+ (M = Fe, Mn; R = alkyl)
Abstract: Chiral bipyrrolidine based iron and manganese complexes [((S,S)-pdp)MII(OTf)2] catalyze the asymmetric epoxidation of various olefins with H2O2 in the presence of carboxylic acid additives with high efficiency (up to 1000 turnover number (TON)) and selectivity (up to 100%), and with good to high enantioselectivity (up to 93% enantiomeric excess (ee)) The enantioselectivity increases with growing steric demand of the acid On the basis of the electron paramagnetic resonance (EPR) spectroscopy and enantioselectivity studies, the active oxygen-transferring species of the above systems can be identified as structurally similar oxometal(V) species of the type [((S,S)-pdp)MV═O(OCOR)]2+ (M = Fe, Mn; R = alkyl)
195 citations
TL;DR: The structures formed by adsorption of carboxyalkylphosphonic acids on metal oxide powders were characterized by solid-state NMR and FTIR-PAS (Fourier transform infrared photoacoustic spectroscopy) as discussed by the authors.
Abstract: The structures formed by adsorption of carboxyalkylphosphonic acids on metal oxide powders were characterized by solid-state NMR and FTIR-PAS (Fourier transform infrared photoacoustic spectroscopy). A series of diacids, HO2C(CH2)nPO3H2 (n = 2, 3, 11, and 15), were deposited on nonporous TiO2 and ZrO2 powders and nanocrystalline ZrO2 with average particle diameters of 21, 30, and 5 nm, respectively. Solid-state 31P NMR, combined with FTIR-PAS, indicates that the phosphonic acid group binds selectively to the surface, producing a monolayer of carboxylic acid terminated chains. The average chain conformation depends on the substrate in addition to the chain length. Ordered samples display thermal order/disorder transitions similar to other self-assembled monolayer systems. The more restricted chain mobility relative to analogous methyl-terminated chains is attributed to hydrogen-bonding among the pendant carboxylic acid groups. These results demonstrate that phosphonic acids are useful for selectively introd...
195 citations
TL;DR: In this paper, atomic force microscopy was used to measure the forces between a silica probe and a carboxylic acid-terminated self-assembled monolayer (SAM) on a gold substrate in the presence of KCl electrolyte solutions of different pH.
Abstract: Atomic force microscopy was used to measure the forces between a silica probe and a carboxylic acid-terminated self-assembled monolayer (SAM) on a gold substrate in the presence of KCl electrolyte solutions of different pH. Silica−silica interaction force measurements were conducted at different pH values to determine the silica probe surface electrostatic potentials under these conditions. The interaction between two silica surfaces is repulsive and can be accurately predicted (except at short distances) by the Derjaguin−Landau−Verwey−Overbeek theory. The interaction between silica and clean gold surfaces exhibits an attractive interaction at neutral pH. The interaction between a silica probe and carboxylic acid-terminated SAM-covered gold substrate was a strong function of the pH value of the electrolyte. The surface electrostatic potentials of the surface-confined monolayers of carboxylic acid were obtained by theoretical fits of the force data to solutions of the complete nonlinear Poisson−Boltzmann e...
195 citations