Salting‐out homogeneous liquid–liquid extraction in narrow‐bore tube: Extraction and preconcentration of phthalate esters from water

In this study a simple and rapid sample preparation technique, homogeneous liquid–liquid extraction based on phase separation in the presence of a salt performed in a narrow‐bore tube, followed by GC‐flame ionization detection has been developed. In this work, sodium chloride and ACN were used as the salting‐out agent and water‐soluble extraction solvent, respectively. The homogeneous solution of water and ACN was broken by addition of the salt. Small volume of ACN was collected on top of the tube and the extracted analytes in the collected phase were determined. It has been successfully used for the analysis of five phthalate esters as model compounds in aqueous sample. Experimental parameters affecting the extraction efficiency such as kind and volume of the water‐soluble organic solvent, length and diameter of the tube, and pH of the sample solution were investigated. Under the optimal conditions, the LODs were between 0.02 and 0.7 μg/L and enrichment factors were in the range of 172–309. In addition, good linearity (between 1 and 5000 μg/L) and high precision on the base of RSD (<8%, C = 600 μg/L, n = 6) were achieved.     

Separation and Characterization of the Prostaglandins by Gas Chromatography and Mass Spectrometry

Abstract

Prostaglandins of the A, B, E and F series, together with 8-iso-E₁, have been separated and characterized by gas chromatography and mass spectrometry through the use of TMSi and MO-TMSi derivatives.

These derivatives are suitable for work with GLC systems with flame ionization detectors. Additional derivatives must be sought for detection by electron capture techniques.     

Synthesis and mesomorphic properties of Schiff base esters possessing terminal chloro substituent

<正>A homologous series of Schiff base esters,4-chlorobenzylidene-4'-n-alkanoyloxyanilines,containing even number of carbons at the end groups of the molecules(C_(n-1)H_(2n-1)COO-,n=4,6,8,10,12,14,16) were synthesized.The mesomorphic properties were investigated by differential scanning calorimetry(DSC) and polarizing optical microscopy(POM).It was found that the end groups of the molecules had an effect on the mesomorphic properties.n-Butanoyloxy was found non-mesogenic,whilst n-hexanoyloxy exhibited monotropic smectic phase.The higher members in this homologous series were enantiotropic smectogens.     

The rhodium-catalyzed selective oxidative Heck reaction of amides with allylic esters

The Rh-catalyzed direct selective oxidation Heck reaction of benzamides with allylic esters has been developed for the synthesis of amides and isoquinolin-1-ones. According to the functional groups on N-atom, benzamides or isoquinolin-1-ones were synthesized under optimal reaction conditions. The ambient catalytic system has good functional group tolerance, afforded corresponding products in moderate to good yields.     

Mechanism study of the conversion of esters to high‐octane‐number aromatics over HZSM‐5

A study of the mechanism of the catalytic transformation of mixed ethyl acetate (EA) + methyl acetate (MA) (50:50 v/v) to hydrocarbons over HZSM‐5 (Si/Al ratio of 9) catalyst was conducted. The reaction was carried out in a continuous fixed‐bed reactor under atmospheric pressure and in the temperature range 250–390°C and with weight hourly space velocity of 3.2 and 4.6 h^?1. The distribution of products including monoaromatics, fused ring aromatics and oxygenates was determined using GC‐MS. The product distribution was controlled by temperature. The oxygenate components (kinetically controlled products) were transformed into aromatics (thermodynamically controlled products) with an increase in temperature. The effluents were benzene‐free or with low content of benzene and toluene. Two intermediates were proposed for this conversion to hydrocarbons over HZSM‐5: cyclobutane‐1,3‐dione and/or acetic acid (AA) as ketene source. Furthermore, AA and mesityl oxide (MO) were selected as potential intermediates in the transformation of mixed EA + MA into hydrocarbons over HZSM‐5. It is suggested that ketene dimerization, the phenolic pool and the condensation reaction between ketene and MO are the probable mechanism routes for AA conversion. Aldol condensation, Michael addition, cracking, isomerization and ketene formation are the presumable pathways for MO conversion over HZSM‐5.     

Silica‐supported Perchloric Acid Catalyzed One‐pot Synthesis of 1,4‐Dihydropyridines

An environmentally friendly and highly efficient procedure for the preparation of 1,4‐dihydropyridines by the reaction between α,β‐unsaturated aldehydes, aromatic amines and β‐keto esters in the presence of silica supported perchloric acid is described.     

Preparation of unsymmetrical dialkyl acetylenedicarboxylates and related esters by enzymatic transesterification

An unexpected highly selective mono-transesterification of symmetrical acetylenedicarboxylates with various alcohols occurred in the presence of Candida rugosa lipase. This reaction allows an efficient preparation of unsymmetrical acetylenedicarboxylates and related α,β-acetylenic esters.