STRUCTURE AND EEI-IAVIOR 017 ORGANIC ANALYTICAL REAGENTS IV. CHELATES 017 z-(o-HYDROSYPMENYL)-13ENZOXAZOLl;:, z-(o-I_LYDROS7L'PH~NYI,)-B~N%O'I'I~IA%OLE AND ~-(o-H'SIDROXYI-'I-~~N~~L)-B~N~O-~I-~IA~O~~IN~.*,** '>Y
A number of organic compounds are known which contain csscntially the same: reactive groups as the important analytical rcapznt S-hydrosycluinoline, but so arranged as to give sis-membered rings when chelating with metal ions. In Paper III' of this series, JOIXNS~ON AND FREISER obtained results which sccmcd to indicate that rcagcnts of this type form metal chelates of lower stability than do those reagents which form five-mcmbcrccl ring chelates. In view of thcsc results it was thought desirable to extend the study of six-mcmbcrcd ring chclntc formers. 2-(o-Hydroxyphcnyl)-bcnzosazolc (I) was chosen for study bccausc preliminary work had shown that this rengcnt reacts rcaclily with a number of metal ions, and also because, unlike certain analogous rcngcnts such as the Schiff bases clcrivcd from salicylaldchydc, it is known to be modcratcly stable in acid solution". The study was cxtcndcd to 2-(o-l~ydroxyp1lcnyl)-benzothiazo1c (II) in order to dctcrmine the cffcct of substituting the larger sulfur atom for the oxazole oxygen.
A study of the reaction between o-aminobcnzcncthiol and salicylaldchyclc, which has been thought to give (II) 5*4 has been shown to actually give the corresponding thiazolim? (111). This substance was found to bc itself a chelating agent and was includccl in the present work for purposes of comparison. I II * 1:~ paper II I, see rcfcrcncc I. ** Abstractccl from tlic thesis submlttccl by ICol3r:iz.r C;. Crrhitr.r:s in parti:il fulfilmcnt of the requirements lor the Ph. 13. &p-cc in Chemistry, August x952. Rcfc~c7aces p. II I<. G. CILARI.ES, II. ~I~ISISI~R VOL. 11 (1954) ~Vfntcvials. The purification of the 1,4-dioxane and the preparation and standardization of nqucous metal pcrchloratc solutions and of standard aqueous sodium hydroxide and aqueous pcrchloric acid have been previously describedO. Metal ion solutions for qualitative tests, containing about 50 milligrams metal ion per milliliter, wcrc prcpnrcd from reagent grade nitrates and distilled water. 2-(o-I-Iydroxyphcnyl)-bcnzoxazolc was prepared from o-aminophcnol and sali-cylamiclc~. It was rccrystallizcd three times from ethyl alcohol-water mixtures and dried in a vacuum dcsiccntor. XT. p. IZG-127' C (corr.). 2-(o-I-lyclrosyl~henyl)-l~cnzothiazolc was prepared in an analogous manner from o-aminobcnzcnctl~iol and salicylamiclc 5. It was vacuum-distilled, rccrystalliacd several times from ethyl alcohol-water mixtures, and dried in a vacuum Clcsiccator. fil. 1'. 132-133Β° C (COrr.). z-(o-I-Iyclrosyphenyl)-bcnzothiazolinc was prepared from o-aminobcnzenethiol and s;~licylaldcl~yclc li. The compound was rccrystnllizcd from ethyl alcohol-water and driccl in vacua. M. p. 136-137" C (corr.) with preheating to 130~ C.