Nazan Tunoglu

Fiber-optic cation determination using crown ether dyes immobilized on polymer membranes ☆

Abstract This study describes the determination and comparison of some cations such as Na+, K+, Ba2+ and Cu2+ in aqueous media by using crown ether dyes immobilized onto thin (0.04 mm) sulfonated kraton polymeric membranes. The studies have been carried out in aqueous solutions first, and in dye–immobilized membrane systems later. The flow-cell system has been found to be more practical in application and had lower response times (30–60 s) as well as detection limits (2.24×10−10–1.19×10-8 mol l−1). The optimum pH range for the formation of ion-dye complexes have been found to be 5 and 9 for the ions above. Since the complexation reactions were reversible it was possible to regenerate the membranes by using HCl solutions and reuse them many times. The same membrane showed high reproducibility and low relative standard deviation. In addition, the interferences of the studied cations to each other and of other various cations during the determinations have also been investigated.

The Immobilization of Ionic and Neutral Crown Ether Dyes to Specific Anionic Polymer Membrane Used as a Chemical Sensor for the Determination of Metal Ions

ABSTRACT In the present study, a neutral crown ether dye (NCED), [4-Nitrophenyl)(4-(4,7,10,13,16-pantaoxa-1 azacyclooctadecyl)phenyl] diazen and an ionic crown ether dye (ICED), 1-Methyl-{2-[4-(4,7,10,13,16-pentaoxa-1 azacyclooctadecyl)phenyl]ethenyl}pyridinium-iodide were synthesized and immobilized on sulfonated hydrocarbon-based block copolymer ionomer to determine Ba2+ and Cu2+ ions in aqueous solution. 5.0×10−2 M ion solutions were used since the best absorbance increase was obtained with this concentration. The increases in absorbances after treating the NCED-immobilized thick polymer membranes (0.20 mm thickness) with Ba2+ and Cu2+ solutions were 0.1488 and 0.2446 in 120 minutes, respectively. The absorbance increases were 0.1664 and 0.3710 during the same time-interval with ICED-immobilized membranes. The response time decreased and absorbance values increased when thin polymer membranes (0.04 mm thickness) were used. The absorbance increases were 0.5088 and 0.8761, respectively in one minute with...

[2+2] CYCLOADDITIONS OF BENZOFURAN-3(2H)-ONE ENAMINES WITH DIMETHYL ACETYLENEDICARBOXYLATE

(2000). [2+2] CYCLOADDITIONS OF BENZOFURAN-3(2H)-ONE ENAMINES WITH DIMETHYL ACETYLENEDICARBOXYLATE. Organic Preparations and Procedures International: Vol. 32, No. 6, pp. 584-588.

Synthesis of Various 2,8-Cyclooctadiene-1,2-dicarboxylates

Reactions of enamines with electrophilic acetylenes such as dimethyl acetylenedicarboxylate (DMAD), diethyl acetylenedicarboxylate (DEAD), methyl propiolate and dicyanoethylene have been extensively studied in the literature.1,2 The two carbon ring expansions which involve [2 + 2] cycloaddition of enamines of cyclic ketones and electron deficient acetylenes followed by thermal rearrangement of the resulting fused cyclobutenes is an established and useful method in organic synthesis. These ring enlargement reactions have been successfully used in the synthesis of medium-sized heterocycles,3–5 azulenes,6 and several natural products including muscone,7 steganone, and velleral.8,9 The mechanism of the reaction of enamine with acetylene derivatives has been thoroughly investigated.1,10–13 It was found that enamine reactions with acetylene derivatives can be affected by many factors. First, a solvent has a remarkable effect on the course of the reactions of acetylene derivatives with enamines. In non-polar solvents, [2 + 2] cycloaddition takes place while in polar solvents pyrrolizines are formed by reaction of the initially formed linear Michael adducts of enamine and acetylene derivatives.13–15 Secondly, the amine moiety on the enamine also affects the rate of reaction and the formation of products as well. The [2 + 2] cycloadducts with the more effective π -electron donating 1-pyrrolidinyl group undergo a thermal rearrangement at room temperature while the analogues with 1-pyrrolidinyl or 4-morpholinyl substituent at the bridgehead sp3-hybridized carbon are thermally stable at room temperature.16 When 2-methylcyclohexanone was subjected to enamine formation reaction with pyrrolidine or morpholine, isomeric mixtures were obtained in each case as reported in the literature.17 6-Methyl-1-(1-pyrrolidinyl)-1-cyclohexene (1) and 2-methyl-1-(1pyrrolidinyl)-1-cyclohexene (3) were obtained in 87% yields in a ratio of 10:90%. Furthermore 6-methyl-1-(4-morpholinyl)-1-cyclohexene (2) and 2-methyl-1-(4-morpholinyl)1-cyclohexene (4) were formed in 79% yield in a 48:52% ratio. We obtained the same results. The [2 + 2] cycloaddition reactions occured with only isomers 1 and 2 which is