Cleavage direction of C-O bond in anion radicals of methyl esters of aromatic acids in aprotic solvents

1982 ◽  
Vol 31 (7) ◽  
pp. 1499-1499 ◽  
Author(s):  
V. P. Gul'tai ◽  
T. Ya. Rubinskaya ◽  
L. M. Korotaeva
Keyword(s):  
Methyl Esters ◽  
Aprotic Solvents ◽  
Aromatic Acids ◽  
Anion Radicals

scholarly journals An enhanced procedure for measuring organic acids and methyl esters in PM<sub>2.5</sub>

2015 ◽  
Vol 8 (3) ◽  
pp. 2379-2407
Author(s):  
F. Liu ◽  
F. Duan ◽  
K. He ◽  
Y. Ma ◽  
K. A. Rahn ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Gas Chromatography ◽  
Organic Acids ◽  
Carboxylic Acids ◽  
Solid Phase ◽  
Methyl Esters ◽  
Aromatic Acids ◽  
Naphthalic Anhydride ◽  
Aliphatic Acids ◽  
Specificity And Sensitivity

Abstract. We have developed an enhanced analytical procedure to measure organic acids and methyl esters in fine aerosol with much greater specificity and sensitivity than previously available. This capability is important because of these species and their low concentrations, even in highly polluted atmospheres like Beijing, China. The procedure first separates the acids and esters from the other organic compounds with anion-exchange solid- phase extraction (SPE), then, quantifies them by gas chromatography coupled with mass spectrometry. This allows us to accurately quantify the C4-C11 dicarboxylic and the C8-C30 monocarboxylic acids. Then the acids are separated from the esters on an aminopropyl SPE cartridge, whose weak retention isolates and enriches the acids from esters prevents the fatty acids and dimethyl phthalate from being overestimated. The resulting correlations between the aliphatic acids and fatty acid methyl esters (FAMEs) suggest that FAMEs had sources similar to those of the carboxylic acids, or were formed by esterifying carboxylic acids, or that aliphatic acids were formed by hydrolyzing FAMEs. In all, 17 aromatic acids were identified and quantified using this procedure coupled with gas chromatography-tandem mass spectrometry, including the five polycyclic aromatic hydrocarbon (PAH) acids 2-naphthoic, biphenyl-4-carboxylic, 9-oxo-9H-fluorene-1-carboxylic, biphenyl-4,4´-dicarboxylic, and phenanthrene-1-carboxylic acid, plus 1,8-naphthalic anhydride. Correlations between the PAH-acids and the dicarboxylic and aromatic acids indicated that the first three acids and 1,8-naphthalic anhydride were mainly secondary, the last two mainly primary.

Biotransformation of Isoprenoids and Shikimic Acid Derivatives by a Vegetable Enzymatic System

2004 ◽  
Vol 59 (3-4) ◽  
pp. 201-204 ◽  
Author(s):  
Wanda Krystyna Mączka ◽  
Agnieszka Mironowicz
Keyword(s):  
Daucus Carota ◽  
Shikimic Acid ◽  
Methyl Esters ◽  
Reversible Reaction ◽  
Apium Graveolens ◽  
Enzymatic System ◽  
Aromatic Acids ◽  
Daucus Carota L ◽  
Enzymatic Systems ◽  
Armoracia Lapathifolia

In biotransformations carried out under similar conditions enzymatic systems from carrot (Daucus carota L.), celeriac (Apium graveolens L. var. rapaceum) and horse-radish (Armoracia lapathifolia Gilib.) hydrolyzed the ester bonds of acetates of phenols or alicyclic alcohols. Nevertheless, methyl esters of aromatic acids did not undergo hydrolysis. Alcohols were oxidized to ketones in a reversible reaction.

scholarly journals Abilities of some higher plants to hydrolyze the acetates of phenols and aromatic-aliphatic alcohols

2014 ◽  
Vol 63 (1) ◽  
pp. 43-48 ◽  
Author(s):  
Agnieszka Mironowicz ◽  
Krystyna Kromer ◽  
Paweł Pawłowicz ◽  
Antoni Siewiński
Keyword(s):  
Petunia Hybrida ◽  
Higher Plants ◽  
Methyl Esters ◽  
Aliphatic Alcohols ◽  
Helianthus Tuberosus ◽  
Aromatic Acids ◽  
Acetate Concentration ◽  
Intact Plants ◽  
Hydrolysis Of ◽  
Different Levels

In the biotransformations carried out under the same conditions, the whole intact plants of <i>Spirodela punctata</i>, <i>Nephrolepis exaltata</i>, <i>Cyrtomium falcatum</i>, <i>Nephrolepis cordifolia</i> and the suspension cultures of <i>Helianthus tuberosus</i>, <i>Daucus carota</i> and <i>Petunia hybrida</i> hydrolyze (partially or totally) the ester bonds of the acetates of phenols and aromatic-aliphatic alcohols and also the menthyl acetate. Nevertheless, the methyl esters of aromatic acids, structurally similar to the former substrates, do not undergo hydrolysis. At the same time, the viability of first four plants was observed for different levels of acetate concentration. The method of continuous preparative hydrolysis of the same acetates was worked out in <i>Cyrtomium falcatum</i> culture.

The preferred radical scavenging mechanisms of fisetin and baicalein towards oxygen-centred radicals in polar protic and polar aprotic solvents

RSC Advances ◽  
2014 ◽  
Vol 4 (61) ◽  
pp. 32228-32236 ◽  
Author(s):  
Jasmina M. Dimitrić Marković ◽  
Dejan Milenković ◽  
Dragan Amić ◽  
Miloš Mojović ◽  
Igor Pašti ◽  
...  
Keyword(s):  
Radical Scavenging ◽  
Aprotic Solvents ◽  
Anion Radicals

The flavonoids fisetin and baicalein have been investigated for their ability to scavenge certain anion radicals.

scholarly journals The Stoichiometric Consequences of Intramolecular or Ion Pair Stabilization of the Anions Formed During Protonation of Anion Radicals in Aprotic Solvents.

1987 ◽  
Vol 41b ◽  
pp. 64-66 ◽  
Author(s):  
Merete Folmer Nielsen ◽  
Ole Hammerich ◽  
Vernon D. Parker ◽  
Bertil Andersson ◽  
Hans-Erik Åkerlund
Keyword(s):  
Ion Pair ◽  
Aprotic Solvents ◽  
Anion Radicals

scholarly journals An enhanced procedure for measuring organic acids and methyl esters in PM<sub>2.5</sub>

2015 ◽  
Vol 8 (11) ◽  
pp. 4851-4862 ◽  
Author(s):  
F. Liu ◽  
F. K. Duan ◽  
K. B. He ◽  
Y. L. Ma ◽  
K. A. Rahn ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Gas Chromatography ◽  
Organic Acids ◽  
Carboxylic Acids ◽  
Solid Phase ◽  
Methyl Esters ◽  
Gas Chromatography Mass Spectrometry ◽  
Aromatic Acids ◽  
Naphthalic Anhydride ◽  
Aliphatic Acids

Abstract. A solid-phase extraction (SPE) pretreatment procedure allowing organic acids to be separated from methyl esters in fine aerosol has been developed. The procedure first separates the organic acids from fatty acid methyl esters (FAMEs) and other nonacid organic compounds by aminopropyl-based SPE cartridge and then quantifies them by gas chromatography/mass spectrometry. The procedure prevents the fatty acids and dimethyl phthalate from being overestimated, and so allows us to accurately quantify the C4–C11 dicarboxylic acids (DCAs) and the C8–C30 monocarboxylic acids (MCAs). Results for the extraction of DCAs, MCAs, and AMAs in eluate and FAMEs in effluate by SAX and NH2 SPE cartridges exhibited that the NH2 SPE cartridge gave higher extraction efficiency than the SAX cartridge. The recoveries of analytes ranged from 67.5 to 111.3 %, and the RSD ranged from 0.7 to 10.9 %. The resulting correlations between the aliphatic acids and FAMEs suggest that the FAMEs had sources similar to those of the carboxylic acids, or were formed by esterifying carboxylic acids, or that aliphatic acids were formed by hydrolyzing FAMEs. Through extraction and cleanup using this procedure, 17 aromatic acids in eluate were identified and quantified by gas chromatography/tandem mass spectrometry, including five polycyclic aromatic hydrocarbon (PAH): acids 2-naphthoic, biphenyl-4-carboxylic, 9-oxo-9H-fluorene-1-carboxylic, biphenyl-4,4´-dicarboxylic, and phenanthrene-1-carboxylic acid, plus 1,8-naphthalic anhydride. Correlations between the PAH acids and the dicarboxylic and aromatic acids suggested that the first three acids and 1,8-naphthalic anhydride were secondary atmospheric photochemistry products and the last two mainly primary.

Calcium ion imaging in plant cells

1993 ◽  
Vol 51 ◽  
pp. 132-133
Author(s):  
Peter K. Hepler ◽  
Dale A. Callaham
Keyword(s):  
Plant Cell Wall ◽  
Cytoplasmic Membrane ◽  
Fluorescent Dyes ◽  
Free Acid ◽  
Methyl Esters ◽  
Free Calcium ◽  
Local Concentration ◽  
Ion Imaging ◽  
Membrane Compartments ◽  
Free Acid Form

Calcium ions (Ca) participate in many signal transduction processes, and for that reason it is important to determine where these ions are located within the living cell, and when and to what extent they change their local concentration. Of the different Ca-specific indicators, the fluorescent dyes, developed by Grynkiewicz et al. (1), have proved most efficacious, however, their use on plants has met with several problems (2). First, the dyes as acetoxy-methyl esters are often cleaved by extracellular esterases in the plant cell wall, and thus they do not enter the cell. Second, if the dye crosses the plasma membrane it may continue into non-cytoplasmic membrane compartments. Third, even if cleaved by esterases in the cytoplasm, or introduced as the free acid into the cytoplasmic compartment, the dyes often become quickly sequestered into vacuoles and organelles, or extruded from the cell. Finally, the free acid form of the dye readily complexes with proteins reducing its ability to detect free calcium. All these problems lead to an erroneous measurement of calcium (2).

Sign in / Sign up

Export Citation Format

Share Document