Analytical Reactions of Hydroxypyridines

Abstract

152 I. IX. 3-NITROSO-2,6-PYRIDINEDIOL (NPD) 173 X. ETHYL-2,4-DIHYDROXY-3-NITROSONICOTINATE (EDHN) 174 XI. HYDROXYPYRIDINE ACIDS AND AMINE 174 XII. SCHIFF'S BASES DERIVED FROM 3-HYDROXYPYRIDINE-2-ALDEHYDE 175 CONCLUSION 176 REFERENCES 178 151 Brought to you by | Purdue University Librari Authenticated Download Date | 5/31/15 7:18 AM SUMMARY Some analytical aspects of the chemistry of hydroxypyridine compounds up to and covering the year 1986 are reviewed. 152 Brought to you by | Purdue University Librari Authenticated Download Date | 5/31/15 7:18 AMHydroxypyridines have been successfully used as sensitive and in many cases selective reagents employing several analytical techniques e.g. spectrophotometry, polarography, potentiometry, fluorimetry, chromatography and solvent extraction /29/. These aspects are reviewed in this article up to and covering the year 1986. II. 2,3-DIHYDROXYPYRIDINE (DHP) DHP was first prepared by Kudernatsch in 1897 /30/ by the alkali fusion of 3-hydroxypyridine. After that, many other methods have been explored for its synthesis /31 -37/ and it has also been found as the by-product in many other syntheses /38-43/. Its characteristics, along with other hydroxypyridines, are presented in Table 1.DHP converts tetrahydrofurans into quarternary ammonium compounds having antibacterial action /44/. This has biological importance also /45,46/. It is very active against salmonella dysentery group bacilli /45/ and is an important intermediate in the bacterial metabolism of the pyridine ring /46/. Spinner and White studied the spectra and ionization constants of substituted 2-hydroxypyridines /47/ including DHP and those of cations and anions of the compounds /48/. The acid dissociation constants of the cationic and neutral species of DHP have been evaluated more precisely and in concentration terms /49/. The stepwise deprotonation of DHP takes place as follows:The overall stability constant of its complex with Fe(III) in 1 .OM HCl has been evaluated. The composition of the complex appears to be FeClHP and the values of the conditional stability constant comes out to be 12.13 with a standard deviation of 0.06. Stability constants of 1:1 bivalent metal complexes with DHP have been determined by Goel et al /50/ in aqueous and 50% dioxan media using the Potentiometrie method. They follow the order: 154 Brought to you by | Purdue University Librari Authenticated Download Date | 5/31/15 7:18 AM Brought to you by | Purdue University Librari Authenticated Download Date | 5/31/15 7:18 AM 157 Brought to you by | Purdue University Librari Authenticated Download Date | 5/31/15 7:18 AM