caa a22 4500 467995613 CHVBK 20180323112556.0 cr unu---uuuuu 170328e19900101xx s 000 0 eng 10.1007/BF01244294 doi (NATIONALLICENCE)springer-10.1007/BF01244294 Investigation of the colour reaction of phenols with MBTH, II: Properties of the isolated products of the reaction with phenol, 2,6-dimethylphenol and 4-methylphenol [Elektronische Daten] [Marie Pospíšilová, Drahomíra Svobodová, Jiří Gasparič, Miloš Macháček] The following model compounds for the study of the oxidative coupling reactions of 2-hydrazono-3-methylbenzothiazoline (MBTH) with phenolic compounds were prepared: thep-coupling products of the reagent with phenol and 2,6-xylenol and theo-coupling product withp-cresol. The proposed structure of the dyes was confirmed. In strongly polar and ionic media the azobetaine form of the products predominates, and in non-polar media the azine structure. The principal physico-chemical properties of the products were determined and the results contributed to formulation of the course of the coupling reaction, and to optimization of the conditions for determination of small amounts of phenolic substances. The violeto-coupling product is less stable than the redp-coupling products, and intramolecularly hydrogen-bonded six-membered ring is assumed to exist in the structure. In acid medium the dyes are mainly monoprotonated, and partly diprotonated in concentrated sulphuric acid medium. The products are stable up to about pH 11. These properties make extraction into low-polarity solvents possible. The dye derived from 2,6-xylenol andp-cresol has not hitherto been prepared. The principal spectral characteristics, γmax(ɛ), of the products in ethanol medium are: 499 nm (4.7 × 104 1·mole−1 cm−1) for the phenol derivative, 486 nm (5.0 × 104) for the 2,6-xylenol product, and γmax 540 nm for thep-cresol product. Springer-Verlag, 1990 MBTH reagent nationallicence phenols nationallicence colour reactions nationallicence quinoneimine dyes nationallicence oxidative coupling nationallicence Pospíšilová Marie Faculty of Pharmacy, Charles University, CS-501 65, Hradec Králové, Czechoslovakia aut Svobodová Drahomíra Faculty of Pharmacy, Charles University, CS-501 65, Hradec Králové, Czechoslovakia aut Gasparič Jiří Faculty of Pharmacy, Charles University, CS-501 65, Hradec Králové, Czechoslovakia aut Macháček Miloš Faculty of Pharmacy, Charles University, CS-501 65, Hradec Králové, Czechoslovakia aut Microchimica Acta Springer-Verlag 102/1-3(1990-01-01), 117-128 0026-3672 102:1-3<117 1990 102 604 https://doi.org/10.1007/BF01244294 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/BF01244294 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Pospíšilová Marie Faculty of Pharmacy, Charles University, CS-501 65, Hradec Králové, Czechoslovakia aut NATIONALLICENCE 700 1- Svobodová Drahomíra Faculty of Pharmacy, Charles University, CS-501 65, Hradec Králové, Czechoslovakia aut NATIONALLICENCE 700 1- Gasparič Jiří Faculty of Pharmacy, Charles University, CS-501 65, Hradec Králové, Czechoslovakia aut NATIONALLICENCE 700 1- Macháček Miloš Faculty of Pharmacy, Charles University, CS-501 65, Hradec Králové, Czechoslovakia aut NATIONALLICENCE 773 0- Microchimica Acta Springer-Verlag 102/1-3(1990-01-01), 117-128 0026-3672 102:1-3<117 1990 102 604 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer