Cathodic reduction of SO2 in the presence of organic dihalides

The reaction of the electrolytically generated SO ₂ ^– anion radical with 1,-dihalides is used for the synthesis of sulfur containing heterocycles like oxathiolane-, oxathiane-, thiane- and thiepane-oxides. 1,2-Dihalides are reductively deblocked to give olefines.

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Kathodische Reduktion von SO₂ in Gegenwart organischer Dihalogenide

Zusammenfassung Die Reaktion des elektrolytisch erzeugten SO ₂ ^– -Anionradikals mit 1,-Dihalogeniden führt zu schwefelhaltigen Heterocyclen wie Oxathiolan-, Oxathian-, Thian- und Thiepanoxiden. 1,2-Dihalogenide geben durch reduktive Eliminierung Olefine.

     

The influence of micellization ofn-decylamine on its basicity and reactivity toward carboxylic acid esters

Micellization ofn-decylamine in aqueous solution leads to substantial decrease in its pK _a, and increase in its reactivity in the nucleophilic substitution ofp-nitrophenylic esters of carboxylic acids (up to 70 times compared to ethylamine which forms no micelles). The influence of cetylpyridinium bromide on the acid-base properties ofn-decylamine and its reactivity was investigated. It was found that the reaction withn-decylamine can be accelerated or retarded depending on the hydrophobicity of the esters. The quantitative characteristics of the mieellar catalytic processes were estimated.Translated fromIzvestiya Akademii Nauk Seriya Khimicheskaya, No. 2, pp. 366–370, February, 1996.     

Preparation,characterization, and mesophase formation of esters of ethylcellulose and methylcellulose

A range of mixed ether-esters of cellulose was prepared from partially substituted ethylcellulose and methylcellulose. The ¹³C-NMR analysis of ethylcellulose with a DS of 2.5 indicated that the hydroxyl groups at carbon six of anhydroglucose units were completely substituted. Acetylation of the ethylcellulose under different conditions yielded (acetyl) (ethyl) cellulose (AEC) samples with acetyl degree of substitution ranging from 0 to 0.5. Fully substituted (propionyl) (ethyl) cellulose (PEC) and (acetyl) (methyl) cellulose (AMC) were also prepared. Chiral nematic liquid crystals were formed in these mixed ester/ethers of cellulose in concentrated solutions of acidic solvents. The critical concentration for the phase separation of the cellulosic solutions depended on the nature of the substituent, the degree of substitution, and the solvent at a given temperature. Methylcellulose solutions in trifluoroacetic acid and dichloroacetic acid form chiral nematic liquid crystals with a left-handed helicoidal structure. The acetylated methyl cellulose samples did not show the reversal of handedness with increasing acetyl content that was previously observed for the corresponding ethylcellulose samples. © 1994 John Wiley & Sons, Inc.     

The Methoxycarbonylation of Vinyl Acetate Catalyzed by Palladium Complexes of [1,2‐Phenylenebis(methylene)]bis[di(tert‐butyl)phosphine]

Palladium complexes of [1,2‐phenylenebis(methylene)]bis[di(tert‐butyl)phosphine] ( 1 ) catalyze the methoxycarbonylation of vinyl acetate (= ethenyl acetate) in the presence of methanesulfonic acid (Scheme 1). High selectivities to ester products can be obtained if free phosphine ligand is in excess over the amount of added acid (Table 1). Selectivities to methyl 2‐acetoxypropanoate, a precursor to lactate esters, can be as high as 3.6 : 1 at low temperature and pressure (Table 2). Replacing ^tBu by ⁱPr groups leads to less‐active catalysts and lower selectivities to the branched product. Replacing the phenylene moiety by a naphthalenediyl moiety also gives lower activity, but with similar selectivity to the phenylene‐based analogues. Linear hydrocarbon‐chain linkers as the backbone instead of the phenylenebis(methylene) linker leads to poor catalysis, except for a propane‐1,3‐diyl linker, which gives good rates but poor branched selectivity (Table 5). The effect of different reaction conditions on the catalysis is discussed. The syntheses of the new xylene‐based diphosphines 2 – 5 with one to four ⁱPr groups replacing the ^tBu groups at the P‐atoms of 1 and of the ligands 6 and 7 based on 1,2‐ and 2,3‐dimethylnaphthalene are also described (Schemes 2 and 3).     

GC–MS analysis of phenolic compounds in fuels after conversion to trifluoroacetate esters

The GC–MS characteristics of trifluoroacetate esters of phenolic compounds are discussed. Linear temperature programmed retention indices and total ion current MS response factors of over 120 phenolic esters are reported. The main GC advantages from analysis of trifluoroacetate esters as compared to plain phenols are enhanced volatility and improved resolution. For example, the elution temperature of a given phenol is typically 50 °C greater than that of the corresponding trifluoroacetate ester. Also, while retention of compounds with two trifluoroacetate groups is only moderately greater than mono esters, underivatized dihydroxy compounds are very difficult to elute from any GC column. Complete resolution of isomeric C₀-, C₁- and C₂-alkylphenol esters is readily achieved on conventional fused silica GC columns; resolution of the corresponding underivatized compounds requires specialized GC columns with low temperature limits. In general, mass spectra of trifluoroacetate esters are more characteristic of a given structure than those of the corresponding phenols and may be more rigorously interpreted towards structural elucidation. A table in the report summarizes some of the more important spectral features used in compound identification. Example applications in analysis of coal-, shale- and petroleum-derived materials are presented. Selected ion monitoring is used to determine individual phenolic components in whole distillates; reconstructed ion chromatograms are used to illustrate distributions of selected species as a function of fuel storage and thermal stress.     

An expedient esterification of aromatic carboxylic acids using sodium bromate and sodium hydrogen sulfite

Treatment of aromatic carboxylic acids and substituted toluenes with a mixture of sodium bromate and sodium hydrogen sulfite in a two-phase system gave the corresponding esters in good yield. The intermediate α-brominated toluene was formed by the in situ generated hypobromous acid. The α-bromotoluene underwent an intermolecular nucleophilic substitution reaction with aromatic carboxylic acids present in the reaction mixture to afford the corresponding esters.     

Determination of C1−C4 fatty acids as p-bromophenacyl esters using glass-capillary gas chromatography and electron-capture detection

Summary A method for the determination of low relative molecular mass carboxylic acids (C₁–C₄) in water is reported. The acids are converted to p-bromophenacyl esters prior to a glass-capillary gas chromatographic separation. By utilizing electron-caputre detection the detectability is substantially improved compared to flame-ionization detection. A comparison of three different ways to treat the water samples and to produce the derivatives is made. It is shown that the , p-dibromoacetophenone reagent decomposes to a small extent which limits the utility of the reagent. Nevertheless a detection limit for formic acid of approximately 2.5 mgl^–1 is obtained. The method is applied to the determination of formic and acetic acids in a paper kraft water sample.     

Retention behaviour of carboxylic acid methyl esters in supercritical fluid chromatography

The study on retention behavior in supercritical fluid chromatography (SFC) is necessary to understand the mechanism of the various interactions in SFC. The retention of SFC in carboxylic acid methyl ester/polymethylsiloxane/CO2 system was studied systematically and the retention behavior of this kind of compounds under various typical operation conditions was described using the method of an alternative unified theory of chromatographic retention. The results illustrated that expression: Ink.= a + b/T + cp + dp/T + ep2/T can be used to describe quantitatively the retention behavior of carboxylic acid methyl ester/polymethylsiloxane/CO2 system in the ranges of reduced density from 0.549 to 1.411. It was also found that the entropy of solute in stationary phase is dependent on the density of supercritical fluid (SF) under typical operating conditions of SFC.     

Esters flash point prediction using artificial neural networks

In this article, an artificial neural network to predict the flash point of 95 esters was implemented. Four variables were used for its development. A neural network with 4‐5‐8‐5‐1 topology was encountered to gain the best agreement of the experimental results with those predicted (square correlation coefficient (R²) and root mean square error were 0.99 and 5.46 K for the training phase and 0.96 and 13.02 K for the testing set). © 2012 Wiley Periodicals, Inc.     

Chemoselective Esterification of Phenolic Acids in the Presence of Sodium Bicarbonate in Ionic Liquids

Chemoselective esterification of phenolic acids with dialkyl sulphates or alkyl halides in the presence of sodium bicarbonate in 1,3‐dialkylimidazolium ionic liquids is reported in excellent yields and less reaction time as compared to organic solvents.