Quinaldinic acid \vas first used as an analytical reagent by IEAY AND &SE', md many papers" have been l~ublishcd on the determination of metals and their separations by this reagent. A new reagent, quinoxalinc-z-carboxylic acid (I) has now been synthesised with a structure similar to quinaldinic acid. The 3-cfiloro (II) and 3-hydroxy (III) derivatives of this reagent have also been prepared and lrave been found to have some analytical applications, The present paper describes the preparation of the reagents, the preparation of their metallic salts, the optimum pH of precipitation of metals from their solutions, the determination of their solubility products, and the analytical applications of tlrese reagents. The themtal behaviour<of the tnetallit salts of the parent reagent were also investigated.
The present studies were made with 6 bivalenl metals, t&z. cogper, cadrniurn, zinc, cobalt, nickel and palladium. Iron forms red colours with reagents I and II, the detailed study of which will be reported at a later date. EXPERIMENTAL 'II%3 preparation of this reagent involves 3 steps, zliz,, preparation of $-toluyl-uiso-glucosamine from D-glucose and +toluidine, and the preparation of 2-a-arabotetrahydroxybutylquinoxaline from this and hydrazine hydrate and o-phenylenediamine ; the z-rr-arabo compound on oxidation with hydrogen peroxide yields quinoxaline-zcarboxylic acid?
A mixture of xoo Q of a-glu.cose, 80 & of fi-toluidine, 25 ml of water and 5 ml of 2 N acetic acid was heated on a steam bath for 30 min. After addition of IOD ml of ethanol, the mass was left overnight and then filtered, and the crystalline residue after washing with alcohul-efher mixture (~3, v/v) was air-dried (yield go 6, m.p. 153").