THIN-LAYER CHROMATOGRAPHY Table I RF Values of the Oxidation Products of p-Phenylenediamine and m-Methoxyphenol(a) 261 Band Color Relative Intensity RF X100 71!::!.' Redish Brown (origin) Strong 0 •ii:!:•:*'.'• Yellow Orange Strong 12.05 •,'•=':. Pink Strong 17.64 Purple Light 21.47 Yellow Strong 26.17 :-: ', Brown Strong 29.70 Yellow Medium 35.58 i!::.: Green Light 40.58 Orange Medium 41.76 :.:::•::•. .:. 1'1 mixlure with hydrogen peroxide oxidant and sodium carbonate base Chloroform' Ethylacetate: Methanol (6: 2: 2) solvent system. i • •.•:', '. ? •.::: •:::.:•There is a great advantage in working with these oxidative dyes. Since the products are •5 colored, it is easy to visualize the progress of the chromatography during development, ito obtain useful information on the presence or absence of certain components, and '. ii even to make a rough estimate of their relative abundance. Although, PDA yields a number of color components in its reaction with alkaline peroxide both alone and with the individual couplers, the dominant composite colors are a purplish-brown for PDA, a green for PDA-resorcinol, and a purplish-blue for PDA-diaminoanisole. The oxidative reaction of resorcinol and diaminoanisole alone or in combination produce negligible color compared with their coupling products with PDA. Self-coupling of PAP provides multicomponent products like other products, but gives a major yellow color. The binary coupling with resorcinol provides green color similar to that of PDA-resorcinol R, but with coupling with DAA the pre- dominant product is a vivid red with blues, greens and relatively few brown components either in primary, or in polymeric products. Chemical structures of the major colors are shown in Fig. 1. With prolonged dye development time, all the above compounds increasingly convert to polymeric compositions of brown components, having a very low mobility on thin layer plates.

262 JOURNAL OF THE SOCIETY OF COSMETIC CHENHSTS TabLe II RF Values of the Oxidation Products of p-Aminophenol and Resorcinol(a) Band Color Relative Intensity RF x100 Brown (origin) Strong 0 Blue Light 7.35 Pink Strong 18.17 Green Medium 26.47 Brownish Red Medium 30.88 Brown Medium 32.35 Red Strong 37.64 Yellow Strong 38.82 (a) 1'1 mixture with hydrogen peroxide oxidant and sodium carbonate base '•. ::i 'i Chloroform' Ethylacetate' Methanol (6: 2:2) solvent system. Reactants Structure of Major Product NH 2 Para-phenylenediamine + .• N• .•NH 2 Hydrogen peroxide H2N N •,• NH 2 Para-phenylenediamine ,• + Resorcinol + Hydrogen peroxide •j•N•NH.•'• H2N'" • HO"- '"•"•'•O • 'XNH Para-phenylenediamine + 2,4 diaminoanisole + Hydrogen peroxide N•OMe H2 N-• •'"•./'H2N'" • "•NH Figure 1. Structure and color of major oxidation products Color on TLC :i: Ilue "!!