Schilt, Alfred Ayars, 1927-
M.S. (Master of Science)
Department of Chemistry
Colorimetry; Chemical tests and reagents
As a part of a continuing study for discovering superior colorimetric reagents for iron, copper and cobalt, the chromogenic properties of a number of recently synthesized ferroin type compounds, including 3-substituted triazines, 3-substituted triazones, 3-substituted triazin-9-ones, and N-substituted amidrazones and related azines, were investigated spectrophotometrically. Among the compounds studied, 2,4-bis(5,6-diphenyl-l,2,H-triazin- 3-yl)pyridine was found to be the most outstanding as an iron chromogen. On the basis of the molar absorptivity of its iron(II) chelate (£- 29,300 at 563 nm in EtOH-CHCl3), it is one of the most sensitive iron reagent found to date. Unfortunately, its insolubility in water and other common solvents retires that it be used in conjunction with a chloroform extraction procedure. Another sensitive colorimetric reagent discovered for iron was 3-(4-phenyl-2-pyridyl)-9H-indeno-(1,2-e)as-triazine-9-ones. It is easy to synthesize, inexpensive, and soluble in dimethylformamide and ethanol mixtures. No extraction process is required. These factors make it worthy of further investigation to develop colorimetric methods for iron(ll) and copper(l) based on its use. An interesting solvent effect was found for the chromogenic reaction of 3-(2-pyridyl)-l,2,4-triazine and 3-(4-methyl)-(2-pyridyl)- 1,2,4-triazin with iron(II). Different molar absorptivities were observed for ethanolic than for aqueous solutions. Furthermore, the iron(II) chelation reactions are pH dependent. Maximum molar absorptivity occurs from pH 1.5 to pH 4.5 and decreases abruptly beyond this pH limit. Such behavior with respect to pH and solvent changes is uncommon for ferroin type chromogens derived from triazine and thus deserves further investigation. Additional evidence was obtained confirming that chromogens with phenyl substituted aromatic systems give more intensely colored metal chelates than do similar chromogens with methyl substituted aromatic systems. It is noteworthy that the 3-substituted triazin-9-ones form more intensely colored metal chelates than do the corresponding 3-substituted triazones. Based on their molecular structure, it is apparent that planarity and cross-ring resonance should be greater in 3-substituted triazones than the corresponding triazin-9-ones. This may be the reason for the higher molar absorptivity of the 3-substituted-triazin-9-one chelates. None of the N-substituted amidrazones or azines were found to be promising as colorimetric reagents for iron, copper or cobalt. The thiazolyl substituted derivatives proved especially unsatisfactory because they only form very weak chelates with iron, copper and cobalt.
Fang, Tsai-Ling, "Spectrophotometric studies on chromogenic properties of some new ferroin-type chromogens" (1974). Graduate Research Theses & Dissertations. 5010.
Northern Illinois University
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