Showing papers on "Carboxylic acid published in 1990"

Extraction of carboxylic acids with amine extractants. 3. Effect of temperature, water coextraction, and process considerations

Abstract: Coextraction of water during extraction of succinic acid by Alamine 336 in different dulents has been measured. The amounts of coextracted water lie in the same order as the solubilities of water in the diluents without amine present. Water coextraction with different acids follows the order fumaric>malonic>maleic=succinic>lactic>acetic. The effects of temperature on extraction of succinic and lactic acids by Alamine 336 with chloroform and methyl isobutyl ketone (MIBK) diluents have been measured. Enthalpies and entropies of complex formation have been derived from the results and are interpreted in terms of the differences in interactions among the species involved. Two approaches for regeneration through back-extraction into an aqueous phase are considered

Platinum group metal alloy catalysts for hydrogenation of carboxylic acids and their anhydrides to alcohols and/or esters

Abstract: Catalyst composition comprising an alloy of at least one noble metal of group VIII of the Periodic Table and at least one metal capable of alloying with the group VIII noble metal, admixed with a component comprising at least one of the metals rhenium, tungsten or molybdenum, used for producing an alcohol and/or a carboxylic acid ester by reacting hydrogen with a carboxylic acid or anhydride thereof.

Sources and sinks of formic, acetic, and pyruvic acids over central Amazonia: 2. Wet season

Abstract: Potential sources and sinks of formic, acetic, and pyruvic acids over the Amazon forest were investigated using a photochemical model and data collected on gas phase concentrations of these acids in the forest canopy, boundary layer, and free troposphere over the central Amazon Basin during the 1987 wet season. It was found that the atmospheric reactions previously suggested in the literature as sources of carboxylic acids (i.e., the gas phase decomposition of isoprene, the reaction between CH3CO3 and a peroxide, and aqueous phase oxidation of CH2O) appear to be too slow to explain the observed concentrations, suggesting that other atmospheric reactions, so far unidentified, could make a major contribution to the carboxylic acid budgets.

Hapten synthesis, antibody development, and competitive inhibition enzyme immunoassay for s-triazine herbicides.

Abstract: Two families of carboxylic acid derivatives of the herbicides atrazine and simazine were synthesized for use as haptens in the development of immunoassays. One family was made by using monosubstituted (alkylamino) cyanuric chlorides and a variety of ω-amino acids, giving spacers of varying lengths attached to one secondary amino group. The second family resulted from the replacement of the 2-chloro group of atrazine or simazine with 3-mercaptopropanoic acid (...)

Inhibition studies on apple polyphenol oxidase

Abstract: Nicolas' Laboratoire de Biochimie Mbtabolique, Station de Technologie des Produits Vbgbtaux, Institut National de la Recherche Agronomique, Domaine Saint-Paul, B.P. 91, 84143 Montfavet CBdex, France Inhibition studies by reductant, carboxylic acid, and halide compounds have been carried out on purified apple polyphenol oxidase

Recent Contributions of Kolbe Electrolysis to Organic Synthesis

Abstract: Carboxylic acids can be decarboxylated by anodic oxidation to radicals (Kolbe-electrolysis) and/or carbocations (non-Kolbe electrolysis). The procedure and necessary equipment is simple, a scale-up easy, the choice of carboxylic acids wide, the selectivity towards radicals or carbocations can be controlled by reaction conditions and the structure of the carboxylic acid, the yields are in general good. The radical pathway can be used for the preparation of e.g. 1,n-diesters, pheromones, or rare fatty acids. Electrolysis in the presence of olefins affords additive dimers and monomers or by intramolecular addition five membered carbocycles and heterocycles. By non-Kolbe electrolysis carboxylic acids can be converted into ethers, acetals, olefins or acetamides. Rearrangements and fragmentations lead to stereospecifically substituted cyclopentanoids and one- or four-carbon ring extensions.

Distribution of hydrophobic ionogenic organic compounds between octanol and water: organic acids

Abstract: The octanol-water distributions of 10 environmentally significant organic acid compounds were determined as a function of aqueous-phase salt concentration (0.05-0.2 M LiCl, NaCl, KCl, CaCl{sub 2}, or MgCl{sub 2}) and pH. The compounds were pentachlorophenol, 2,3,4,5-tetrachlorophenol, (2,4,5-trichlorophenoxy)acetic acid, 4-chloro-{alpha}-(4-chlorophenyl)benzeneacetic acid, 2-methyl-4,6-dinitrophenol, (2,4-dichlorophenoxy) acetic acid, 4-(2,4-dichlorophenoxy) butanoic acid, 3,6-dichloro-2-methoxybenzoic acid, 2,3,6-trichlorobenzeneacetic acid, and 2-(2,4,5-trichlorophenoxy)propionic acid. The experimental results were interpreted quantitatively with an equilibrium model that accounts for acid dissociation in the aqueous phase and partitioning into the octanol phase by the neutral organic species, free inorganic and organic ions, and ion pairs. The partition constants for the neutral ion pairs correlate well with the partition constants of the neutral acids. Two experiments address the applicability of these octanol-water distribution data to the distribution of ionogenic compounds in the environment: the distribution of 2-methyl-4,6-dinitrophenol on a natural sorbent as a function of salt concentration (NaCl and CaCl{sub 2}) and pH, and competitive adsorption of pentachlorophenol and 2,3,4,5-tetrachlorophenol on an environmental sorbent.

An approach to the design of molecular solids. The ureylenedicarboxylic acids

Abstract: The crystal structures of a series of ureylenedicarboxylic acids have been determined as part of a project directed toward the design of molecular solids. The ureylenedicarboxylic acids were chosen for study because they were predicted to form a two-dimensional hydrogen-bonded network. This two-dimensional network is the result of two orthogonal linear arrays of self-complementary hydrogen-bonded functionalities, the dicarboxylic acids and N,N{prime}-disubstituted ureas, being present in the same molecule. The simplest molecules of the series, 2,2{prime}-ureylenediacetic acid (1), 3,3{prime}-ureylenedipropionic acid (2), and 4,4{prime}-ureylenedibutyric acid (3) as well as the simplest ureylene derived from a dipeptide, N,N{prime}-carbonylbisglycylglycine (4) were synthesized and studied by using x-ray crystallographic techniques. Each molecule was found to crystallize to give the predicted solid-state structure.

Ionically cross-linkable polyphosphazene: poly(bis(carboxylatophenoxy) phosphazene) and its hydrogels and membranes

Abstract: Hexachlorocyclotriphosphazene and poly(dichlorophosphazene) react with the sodium salt of ethyl p-hydroxybenzoate to give small molecule cyclic and high polymeric phosphazenes with aryloxy ester side groups; reaction of these compounds with potassium tert-butoxide brings about complete hydrolysis of the ester groups to yielding aqueous media-soluble, carboxylic acid bearing cyclic and high polymeric phosphazenes; the carboxylic acid bearing high polymer formed ionic cross-links when treated in aqueous media with salts of di- or trivalent cations yield hydrogels and membranes. The cross-linked gels were stable in neutral or strongly acidic aqueous media, but the cross-linking process was reversed in basic aqueous solutions of excess monovalent cations.

Aristolochic acid binds covalently to the exocyclic amino group of purine nucleotides in DNA

Abstract: The plant extract aristolochic acid (AA) has been used as a herbal drug in many cultures since antiquity. In 1982 AA was shown to be mutagenic and a strong carcinogen in Wistar rats. The crude mixture consists of five nitrophenanthrene carboxylic acid derivatives with aristolochic acid I [AA I; 8-methoxy-6-nitro-phenanthro-(3,4-d)-1,3-dioxolo-5-carboxyli c acid] being the major component. The isolated compound has been found to be mutagenic in the Ames assay. The major metabolite of AA I formed under anaerobic conditions in vitro and excreted in vivo in several species including man, is the reduction product aristolactam I. Using the 32P-postlabeling assay, we could show that AA I forms covalent DNA adducts upon metabolic activation in vitro and in vivo in different organs in the rat. Xanthine oxidase, a mammalian nitroreductase, has served as a sufficient model system mimicking the reductive route of in vivo activation of carcinogenic nitroarenes. This paper reports on two major fluorescent adducts of AA I formed by in vitro reaction of AA I with xanthine oxidase and deoxyguanosine or deoxyadenosine. After isolation and purification by preparative HPLC the adducts were characterized by 1H-NMR, FAB mass, UV/Vis and fluorescence spectroscopy. Their structures were elucidated as 7-(deoxyguanosin-N2-yl)-aristolactam I and 7-(deoxyadenosin-N6-yl)-aristolactam I. These findings are in marked contrast to the results reported for other nitroaromatic carcinogens, where C8-modified deoxyguanosine adducts predominate and N2-substituted deoxyguanosine derivatives are found as minor reaction products. Our results suggest a cyclic N-acylnitrenium ion with delocalized positive charge as the ultimate carcinogenic species, binding preferentially to the exocyclic amino group of purine nucleotides in DNA.

Extraction equilibria of organic acids with tri-n-octylphosphineoxide

Abstract: The extraction equilibrium of organic acids (acetic, glycolic, propionic, lactic, pyruvic, butyric, succinic, fumaric, maleic, malic, itaconic, tartaric, citric and isocitric) with tri-n-octylphosphine oxide (TOPO) was measured. The solvation numbers of the acids were the same as the numbers of the carboxyl groups on each acid molecule. The extraction equilibrium constant was controlled by the hydrophobicity of the acid when hexane was used as a diluent.

Acidities of OH compounds, including alcohols, phenol, carboxylic acids, and mineral acids

Abstract: Les acidites en phase gazeuse de divers alcools, halogenoalcools, phenol, acides carboxyliques, et acides mineraux sont reproduites par un traitement theorique empirique des effets du substituant (X), de la polarisabilite (P), du champ/inducteur (F), et de la delocalisation des electrons π (resonance, R) dans XOH

Adventitious rooting in hypocotyls of sunflower (Helianthus annuus) seedlings, 3: The role of ethylene [1-aminocyclopropane-1-carboxylic acid, aminoethoxyvinylglycine, 1-(malonylamino) cyclopropane-1-carboxylic acid, silver nitrate, silver thiosulphate]

Abstract: The effect of brief application (usually for 3 h) of various growth regulators and their antagonists on the production of adventitious root primordia in sunflower hypocotyls over a 3 day period, was investigated. Gibberellic acid inhibited, while an inhibitor of gibberellin biosynthesis promoted rooting. Low concentrations of cytokinins increased, but higher levels inhibited primordia formation. Auxin was able to stimulate or inhibit root production, depending upon the quantity applied, and triiodobenzoic acid applied to the top of the hypocotyls lowered the rate of root formation. From experiments in which benzyladenine, silver nitrate and benzyl isothiocyanate were supplied to the hypocotyl for various 3 h periods after root removal, we concluded that some of the important events necessary for adventitious root production occur during the first few hours after excision of the original root system. We also suggest that the hypocotyl cells on the first day go through a phase during which primordia production is blocked by endogenous ethylene and on the second day enter a phase during which endogenous ethylene promotes rooting.

Peroxy acid generator

Abstract: We have found a new and useful process to generate peroxy acid sanitizing and bleaching compositions at the point-of use, the-process comprising introducing hydrogen peroxide and a carboxylic acid into a reactor at about 0.1 to 10 moles of hy-drogen peroxide per mole of acid, and contacting the hydrogen peroxide and carboxylic acid in the presence of a sulfonic acid resin and in the substantial absence of active metal ions which forms an aqueous peroxy acid composition at a concentration from about up to 20 wt-%. Using this process, warewashing, laundry sanitizing and bleach, and hard surface sanitizing composi-tions can be produced.

Secondary porosity revisited; the chemistry of feldspar dissolution by carboxylic acids and anions

Abstract: Carboxylic acids in subsurface waters have been proposed as agents for dissolving feldspars and complexing aluminum to create secondary porosity in sandstones. Previously published experimental work indicated high aluminum mobility in the presence of carboxylic acid solutions. In order to further evaluate aluminum mobility, alkali feldspar dissolution experiments were run at 100 degrees C and 300 bars in the presence of mono- and dicarboxylic acids and their anions. Experimental results imply that under reservoir conditions, aluminum-organic anion complexes are insignificant for acetate and propionate and possibly significant for oxalate and malonate. Propionate appeared to inhibit alkali feldspar dissolution and, hence, may retard aluminum mobility. Dissolution of feldsp r in the presence of oxalic and acetic acid can be explained by enhanced dissolution kinetics and greater aluminum mobility under low-pH conditions. The general absence of such low-pH fluids in subsurface reservoirs makes this an unlikely mechanism for creating secondary porosity. Also, the thermal instability of oxalate and malonate limits their aluminum-complexing potential in reservoirs at temperatures above 100 degrees C.

A New and Facile Method for the Direct Preparation of α-Hydroxycarboxylic Acid Esters from α,β-Unsaturated Carboxylic Acid Esters with Molecular Oxygen and Phenylsilane Catalyzed by Bis(dipivaloylmethanato)manganese(II) Complex

Abstract: In the presence of a catalytic amount of bis(dipivaloylmethanato)manganese(II) complex, the oxygenation of benzyl crotonate with molecular oxygen and phenylsilane proceeds smoothly under a mild condition to give benzyl 2-hydroxybutyrate in high yield. The reaction provides a new and convenient method for the direct preparation of various α-hydroxycarboxylic acid esters starting from α,β-unsaturated carboxylic acid esters. The influence of substituents of olefins on regioselectivity is also studied.

Carboxylic-acid and sulphonic-acid amides

Abstract: The novel carboxylic acid and sulphonic acid amides of the formula… R -A-(W)a-X-(CH2)b-(Y)c-B-Z-COOR (I) in which R , A, W, X, Y, B, Z, R, a, b and c have the meaning given in the description, can be used in the treatment of thromboses, apoplexy, cardiac infarcts, inflammations, arteriosclerosis and tumours. They are prepared by removal of the protective groups in corresponding compounds having protected amidino or guanidino groups.

Steroidal A ring aryl carboxylic acids: a new class of steroid 5 alpha-reductase inhibitors.

Abstract: A series of 17 beta-carbamoyl-1,3,5(10)-estratriene-3-carboxylic acids has been prepared and evaluated in vitro as inhibitors of human and rat prostatic steroid 5 alpha-reductase (EC 1.3.1.30). Potent inhibition of the human enzyme, in particular, was observed and preliminary studies using rat enzyme suggest that the inhibition results from the formation of an enzyme-NADP(+)-inhibitor complex. The compounds were synthesized from estrone, generally employing a differentiated bis-triflate carbonylation strategy.

Effect of ring size variation within lipophilic crown ether carboxylic acids on the selectivity and efficiency of competitive alkali-metal cation solvent extraction into chloroform

Abstract: Competitive solvent extraction of alkali-metal cations from aqueous solutions into chlororform by a series of lipophilic crown ether carboxylic acids with varying ring sizes is reported. Extraction selectivity for Li{sup +} is observed for lipophilic crown ether carboxylic acids with 12-15-membered polyether rings containing four oxygen atoms. For lipophilic 14-crown-4-carboxylic acids, very high Li{sup +}/Na{sup +} selectivity coefficients of 17-20 are observed with no detectable extraction of K{sup +}, Rb{sup +}, or Cs{sup +}. Lipophilic crown ether carboxylic acids which contain 15-crown-5, 18-crown-6, and 21-crown-7 rings exhibit good selectivities for Na{sup +}, K{sup +}, and Cs{sup +}, respectively. In contrast, poor extraction selectivity is observed for lipophilic crown ether carboxylic acids with 24-crown-8, 27-crown-9, and 30-crown-10 rings.