Carboxylic acid

About: Carboxylic acid is a research topic. Over the lifetime, 48544 publications have been published within this topic receiving 605696 citations.

Esterification of different acids over heterogeneous and homogeneous catalysts and correlation with the Taft equation

Abstract: Esterification of acetic, propanoic and pentanoic acid with methanol, ethanol, 1-propanol, 2-propanol, butanol and 2-butanol was studied in the presence of a fibrous polymer-supported sulphonic acid catalyst, Smopex-101. The reaction temperature in the experiments was 60 °C. Comparative experiments were carried out on an ion-exchange resin, Amberlyst 15 and with a homogeneous catalyst, liquid HCl. The effect of different molar ratios between the reactants (acid and alcohol) on the reaction rate was investigated. The rate constants were related to the substituent effects of the reacting molecules according to the Taft equation. The substituent effects of alcohols were found to follow the Taft relationship, which was not the case for the acids. The experimental results were modelled according to a simple second-order model and a more advanced adsorption-based model. The adsorption-based model, which includes the adsorption of carboxylic acid and water and is consistent with structure–activity relationship, was superior to the second-order model.

Fluorescent Labeling of Fatty Acids with 9-Anthryldiazomethane (ADAM) for High Performance Liquid Chromatography

Abstract: A novel method for rapid and simple fluorescent labeling of carboxylic acids with 9-anthryldiazomethane (ADAM) for HPLC is described. This reagent is stable in solution and highly reactive with carboxylic acids. Esterification proceeds at room temperature without catalyst. The labeled compounds are separated using a reversed-phase system and determined with a flow-through flurometer. Picomole level of fatty acids are determined by this method.

Sialic Acid-Imprinted Fluorescent Core-Shell Particles for Selective Labeling of Cell Surface Glycans.

Abstract: The expression of cell surface glycans terminating with sialic acid (SA) residues has been found to correlate with various disease states there among cancer. We here report a novel strategy for specific fluorescence labeling of such motifs. This is based on sialic acid-imprinted core-shell nanoparticles equipped with nitrobenzoxadiazole (NBD) fluorescent reporter groups allowing environmentally sensitive fluorescence detection at convenient excitation and emission wavelengths. Imprinting was achieved exploiting a hybrid approach combining reversible boronate ester formation between p-vinylphenylboronic acid and SA, the introduction of cationic amine functionalities, and the use of an NBD-appended urea-monomer as a binary hydrogen-bond donor targeting the SA carboxylic acid and OH functionalities. The monomers were grafted from 200 nm RAFT-modified silica core particles using ethylene glycol dimethacrylate (EGDMA) as cross-linker resulting in a shell thickness of ca. 10 nm. The particles displayed strong affinity for SA in methanol/water mixtures (K = 6.6 × 10(5) M(-1) in 2% water, 5.9 × 10(3) M(-1) in 98% water, B(max) ≈ 10 μmol g(-1)), whereas binding of the competitor glucuronic acid (GA) and other monosaccharides was considerably weaker (K (GA) = 1.8 × 10(3) M(-1) in 98% water). In cell imaging experiments, the particles selectively stained different cell lines in correlation with the SA expression level. This was further verified by enzymatic cleavage of SA and by staining using a FITC labeled SA selective lectin.