OXIDATIVE HAIR DYEING 113 0.5 D i i i ß i ß 500 600 Wavelength, nm Figure 2. Visible spectrum of 7-amino-g-methylphenoxazime in 0.1M HC1 (A and F) pH 11.2 aqueous Na=O• (B) 0.1M NaOH (C) 12M HC1 (D) and coned H2SO• (E). A-E, 5 x 10-6M solutions in 4.0-cm cells F, 5 x 10-=M solution in 0.5-cm cell In contrast, we find that oxidation of mixtures of 2,5-diaminoanisole and 4- methyl-3-aminophenol gives rise to a magenta dye which, even in dilute solu- tion, undergoes almost immediate intramolecular cyclization to the phenoxa- zinium salt. The latter can be extracted from hair dyed with the above mix- ture and its formation accounts for the extremely stable violet coloration which has been reported to be produced (33). Apparently, the oxidative cou- pling produces the indamine (XVII) which undergoes nonoxidative cycliza- tion with the elimination of methanol to give (XV). Except as otherwise indicated above, all the compounds (IX)- (XVI) can either be extracted from or observed to have been formed in hair dyed with the appropriate reactant mixture. Furthermore, they are the major colored species formed in oxidative dyeing with p-diamines and m-disubstituted couplers. Spectral Properties o[ Binuclear Dyes The colors produced in hair by the various classes of binuclear dyes have been mentioned above and it is pertinent at this point to consider their spec- tral properties.

114 JOURNAL OF TIlE SOCIETY OF COSMETIC CHEMISTS 0 TIME IN MIN 7.5 • i 1.0 t • • 14.5 ._ o0. 5 27 71 I I I 400 500 600 Wavelength, nm Figure 3. Spectrophotometric course of the decomposition of a dilute solution of g-hydroxy- 5-methylindamine, showing the absence of formation of the phenoxazime (broken line) Table V Spectra of Indo Dyes in Neutral Solution Dye Indoaniline 2-methoxy 2-hydroxy 2-amino Indamine 2-methoxy 2-hydroxy-5-methyl 2-amino X,..x (log e) Substituent Shift (nm) 554 (4.05) ... 538 (3.0o) -].6 484 (3.93) --70 511 (3.98) --43 672 (4.60) ... 653 (...) --19 504 (3.99) --168 552 (4.13) --120 Experience has shown that the colors produced on hair are similar to thosc pertaining in neutral aqueous solutions of the dyes. Table V gives spectra for a variety of related indamine and indoaniline dyes. It can be seen that the introduction of amino, hydroxy, or methoxy groups into the 2-position of the parent indo dye results in a marked hypso-