Strong Carboxylic Acids Research Articles

A two-component, non-aqueous route to silica gel

A new means for generating silica gel has been developed. Simple two component systems comprising tetraalkoxysilanes and strong carboxylic acids such as formic acid can react rapidly to give transparent monolithic gels. The acid serves as solvent, water source, and catalyst for both hydrolysis and condensation. Water need not be present as an initial reactant; it is generated in situ during the reaction. The gelation reaction is at least two orders of magnitude faster than those conducted in conventional acid-catalyzed aqueous systems at comparable pH*. Kinetic evidence indicates a lowering of the activation energy of condensation reactions, believed to be associated with reaction of silyl carboxylates and silanol groups. Physical properties of the dry gels such as bulk density more closely resemble conventional acid-catalyzed gels than those associated with other rapidly gelling systems. Dry gels often exhibit porosity so fine that nitrogen (at 77°K) is not absorbed at significant rates. Independent evidence of porosity arises from comparison of skeletal and bulk densities, sample immersion in water and adsorption isotherms of CO2.

脂肪族カルボン酸陽子附加物のＯ‐Ｈ結合エネルギーとアルミニウムの腐食制御作用の考察

from EB (O-H*) = ΔEP-EA (H+). The electron affinity of the H+ ion EA (H+) was estimated as the same of value of ionization potential of the H atom, IP (H) = 13.598eV. ΔEP is the difference of EP among the structures of II-VI; ΔEP = EP (II)-EP (III, IV, V, VI). The values (in kJ/mol) obtained of EB (O-H*) (for the structure IV) are formic acid (527.988)>acrylic acid (490.443)>propionic acid (485.717). This order describes that the strong carboxylic acid makes its protonated acid stable and the order is the same of that of corrosion inhibition of cathodic reaction by the acids on Al. Each of the four carboxylic acids makes their protonated acids and it describes that the carboxylic acids decrease the H+ ion and inhibit the cathodic reaction 1/2O2+2H++2e→H2O. This is corrosion inhibition effect on the Al cathode and the strong acid has the large effect.

Direct Optical Resolution of Carboxylic Acids by Chiral HPLC on Tris(3,5-dimethylphenylcarbamate)s of Cellulose and Amylose

Abstract A variety of racemic carboxylic acids have been for the first time directly resolved by normal-phase, high-performance liquid chromatography using a hexane-2-propanol eluting system containing a small amount (≈1%) of a strong carboxylic acid, like formic acid, trichloroacetic acid, and trifluoroacetic acid.

Copper-catalyzed acetoxylation (hydroacetoxylation) of butadiene: A comparison with the hydrocyanation reaction

Copper bromide catalyzes the monoaddition of acetic acid to butadiene (and less effectively to substituted conjugated dienes) yielding mixtures of acetoxybutenes. The presence of LiBr as additive is necessary for efficient catalytic activity. The efficiency of the catalyst can be further improved by adding halogenated additives and strong carboxylic acids. In contrast, complexing ligands (e.g., PPh 3 polyethers) inhibit the catalyst activity. When compared with the copper-catalyzed hydrocyanation of butadiene, the regioselectivity of the acetoxylation is low, easy interconversion of the linear and branched isomeric products being achieved under the reaction conditions, the 1,4-isomer corresponding to the thermodynamically controlled one.

ChemInform Abstract: CATALYTIC CONTROL OF REACTIONS OF DIPOLES AND CARBENES; AN EASY AND EFFICIENT SYNTHESIS OF CYCLOHEPTATRIENES FROM AROMATIC COMPOUNDS BY AN EXTENSION OF BUCHNER′S REACTION

AbstractDie Benzole (I) reagieren mit Diazoessigsäuremethylester (II) hauptsächlich zu den Cycloheptatrienen (III), deren Isomerenverteilung untersucht wird.

Catalytic control of reactions of dipoles and carbenes; an easy and efficient synthesis of cycloheptatrienes from aromatic compounds by an extension of Buchner's reaction

Rhodium salts from strong carboxylic acids [particularly rhodium(II) trifluoroacetate] are novel and highly efficient catalysts for the preparation of substituted cycloheptatriene carboxylates from aromatic hydrocarbons and diazo-esters, and in contrast with the classical Buchner procedures these rhodium catalysts lead specifically to the 1-isomer (3), avoiding its subsequent prototropic conversion into conjugated isomers.

The Defensive Chemistry of Land and Water Beetles

AbstractWherever life forms have arisen, they have had to defend themselves, even on the lowest levels, against their own kind. Darwin called this the struggle for life. The following discussion shows that this struggle can be carried on chemically with compounds of widely differing classes. Examples of defensive substances found are hot quinones in bombardier beetles, and weak and strong carboxylic acids, phenols, terpenes, steroids, and alkaloids in other Adephaga.