REACTION OF PPD AND BENZENE DERIVATIVES 435 The colorimetric data of the pigment deriving from the couple 2-amino-4-(2-hydroxy- ethylamino)anisole sulfate (AHA) and PPD (see Table I) show that, in all the range of pH values under study, L, a*, and b* values are typical of the purple-blue color. TLC shows at pH 7.5 the presence of a strong dark brown pigment, with Rf = 0, and a large and strong blue band, with Rf = 0.1–0.25. At pH 9.5 the band with Rf = 0 is light (yellow brown) while the blue band is very strong. Furthermore, the blue band turns slowly to brown by exposure to daylight (Table V). Corbett states that the reaction rate between PPD and aromatic m-diamines is very high. The analysis of the color formed in the tested pH range really suggests that the blue ami- noindamine 3 or the trinuclear derivative 5 are always the main products of the reaction. In spite of this, the pigment formed is very sensible to weathering also in the absence of the direct action of sunlight. The color fades and turns from blue to a purple shade and fi nally to dark brown or dark red (Table V). Table IV Weathering Effect on Color Fastness of PPD-AP at pH 10 without Direct Sunlight Exposure Colorimetric Parameters Days 0 4 7 11 14 18 24 L 27.59 28.56 29.04 29.26 29.4 29.89 30.29 a* 8.31 7.15 6.75 6.36 6.36 5.88 5.93 b* 1 2.54 3.15 3.62 3.75 4.3 4.43 Table V Weathering Effect on Color Fastness of PPD-AHA without Direct Sunlight Exposure Colorimetric Parameters Days 0 4 7 11 14 18 24 pH 9.0 L 18.39 18.72 21 24.25 26.13 28.34 31.05 a* 6.61 4.8 4.05 3.44 3.03 3 2.58 b* −14.38 −10.04 −6.91 −3.77 −2.08 −0.55 −1.32 pH 9.5 L 13.36 13.66 14.36 15.41 16.65 18.11 20.24 a* 4.46 3.97 3.75 3.53 3.38 3.44 3.18 b* −9.13 −8.1 −7.08 −5.84 −4.8 −3.68 −2.25 pH 10.0 L 13.8 14.46 15.59 17.27 18.89 20.83 23.66 a* 3.95 2.78 2.13 1.74 1.56 1.77 1.68 b* −9.98 −7.85 −5.88 −3.71 −2.09 −0.52 1.31 pH 10.5 L 15.86 17.11 19.46 22.25 24.2 27.19 30.92 a* 3.82 2.1 1.23 0.9 0.74 0.86 0.71 b* −12 −8.41 −5.19 −1.87 0.21 2.1 3.9

JOURNAL OF COSMETIC SCIENCE 436 CONCLUSIONS The whole of the experimental data show how it is possible to follow satisfactorily the variation of the pigment composition obtained from the reactions under a study carried out at different pH values by colorimetric analyses. In fact, if the colorimetric data can be considered a good descriptor of the formed pigment, our hypothesis of using the refl ec- tance as an innovative parameter for the prevision of the color yielded by such reactions can be asserted. Furthermore, the obtained data show that the color formed on the wool may be considered a good expression of the whole of the chromatic features of the major components present in the reaction solution. The results agree with the hypothesis that the wool fi ber does not interact chemically with the colored molecules. The weathering experiments show that, for all the couplers, the color decay, near to the destruction of the colored molecules, displays color alterations similar to those shown by the same colored molecules on an inert support like the silica gel used for the TLC. Since the color fastness on the wool is greater than that on TLC plates, we can assume that the colored molecules reside in the interior of the wool fi ber. The data seem to exclude any chemical interaction between the support and the dye formation, and as a consequence, wool seems to be an ideal substrate for a preliminary study of the application of colorim- etry as a new base of inspection in color prediction. ACKNOWLEDGMENTS This work was carried out with the fi nancial support of Tocco Magico (Italy). REFERENCES (1) J. F. Corbett, Benzoquinones imines. Part I. p-Phenylendiamine-ferricyanide and p-aminophenol-ferri- cyanide redox systems, J. Chem. Soc. B, 207–212 (1969). (2) J. F. Corbett, Benzoquinones imines. Part IV. Mechanism and kinetics of the formation of Bandrowski’s base, J. Chem. Soc. B, 818–822 (1969). (3) J. F. Corbett, Benzoquine imines. Part VI. Mechanism and kinetics of reaction of p-benzoquinone di- imine with m-phenylendiamines, J. Chem. Soc. B, 827–835 (1969). (4) J. F. Corbett, Benzoquinone imines. Part VII. The mechanism and kinetics of reaction of p-benzoqui- none di-imine with monohydric phenols and the ultraviolet, infrared, and nuclear magnetic resonance spectra of the resulting indoanilines, J. Chem. Soc. B, 1418–1426 (1970). (5) J. F. Corbett, Benzoquinone imines. Part IX. Mechanism and kinetics of reaction of p-benzo quinone di-imine with m-aminophenols, J. Chem. Soc. (Perkin II), 539–480 (1972). (6) J. F. Corbett, The role of meta difunctional benzene derivatives in oxidative hair dyeing. I. Reaction with p-diamines, J. Soc. Cosmet. Chem., 24, 103–134 (1973). (7) J. F. Corbett, Chemistry of hair colorant processes—Science as an aid to formulation and development, J. Soc. Cosmet. Chem., 35, 297–310 (1984). (8) J. S. Mukund, W. S. Tolgyesi, and A. D. Britt, Cooxidation of p-phenylendiamine and resorcinol in hair dyes, J. Soc. Cosmet. Chem., 23, 853–861 (1972). (9) R. J. Crawford and C. R. Robbins, A replacement for Rubine dye for detecting cationics on keratin, J. Soc. Cosmet. Chem., 31, 273–278 (1980). (10) M. Dolinsky, C. H. Wilson, H. H. Wisneski, and F. X. Demers, Oxidation products of p-phenylendi- amine in hair dyes, J. Soc. Cosmet. Chem., 19, 411–422 (1968).