OXIDATION PRODUCTS IN HAIR DYES 419 40' ß • •o- 0 I Figure 7. TIME (DAYS) Insoluble oxidation products formed vs. reaction time Analytical data for the composition of precipitates, material remaining in solution, and total reaction products obtained after a period of twelve days are shown in Table I. OXIDATION IN CONCENTRATED I-I202 A similar series of reactions was carried out with 4.0 g of p-phenylenediamine in 267 ml of approximately 6% NH4OH plus 267 ml of 6% H•.O2. This represents a molar ratio of peroxide to phenylenedi- amine of approximately 12 to 1 with an over-all peroxide concentration of 3%, and is believed to approximate actual hair-dyeing practice. Under these conditions, somewhat different results were obtained. UV Table I Oxidation Products of 4.0-g Samples of p-Phenylenediamine in Dilute Peroxide Composition of Precipitates Total Products Material in After Solution After Average 12 Days 12 Days (%) (rag) (mg) (rag) Band I Trace ... Band II 1.0 24 Band III 6.5 87 Band IV 83.0 1665 Band V (by difference) 9.5 193 Unreacted PPD 13 13 16 40 48 135 35 1700 0 193 1600 Total 3681 Unaccounted 319

420 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS spectrophotometry shows the phenylenediamine to disappear completely in approximately ten hours the amount of insoluble material is much less than in the case of dilute peroxide and shows a gradual decrease after reaching a maximum, apparently due to further oxidation to water- soluble materials (Fig. 7). As in the previous series, all precipitates were found to have practically the same composition regardless of re- action time (one to 16 days). Spectrophotometric analysis of the tiltrates showed only the presence of p-nitroaniline other ultraviolet absorbers were present in only trace amounts. Analytical data for the composition of precipitates and total reaction products after a period of three days are shown in Table II. In an attempt to identify the "unaccounted" material, the tiltrate was evaporated to dryness under vacuum in a rotary evaporator. The solid thus obtained was washed with ether to remove p-nitroaniline, and the residue (2.8 g) was fractionally crystallized from alcohol. The first fraction thus obtained was identified from its infrared spectrum as ammonium formate. Subsequent fractions, as well as the alcohol-in- soluble material, gave spectra very similar to those of ammonium acetate, ammonium oxalate, and ammonium tartrate, but were not sufficiently pure for positive identification. There is no doubt, however, that much of the "unaccounted" material is due to oxidation to simple aliphatic carboxy acids. Our results also indicate an appreciable amount of oxidation to CO2 and H20. Table II Oxidation Products of 4.0-g Samples of p-Phenylenediamine in Concentrated Peroxide Composition of Precipitates Total Products Average After 3 Days After 3 Days (%) (rag) (rag) Band I 1.2 52 215 Band II 0.3 1 1 Band III 8.9 37 37 Band IV 70.4 296 296 Band V 19.2 81 81 Unreacted PPD 0 0 0 Total 630 Unaccounted 3370