318 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS TABLE 1,--CONSTITUTION OF THE LAC COMPLEX Per Cent by Weight Aleuritic acid Shellolic acid and homologues Kerrolic acid Butolic acid (approx.) Esters of wax alcohols and acids (approx.) Unidentified neutral material, dyes, etc. Unidentified polybasic acid interesters 46 27 5 1 2 7 12 100% Figure 1 shows the structure of shellolic acid. This was unequivocally determined last year by Yates and Field (15). It is a sesquiterpene acid having the skeletal structure of a rather rare sesquiterpene: cedrene, which occurs in only a few known plant species. The spatial structure shown is according to that deduced for cedrene by Stork and co-workers (16,17). Yates and Field state that shellolic acid forms a lactone with great ease through the primary hydroxyl group Figure 1.--Shellolicacid: m.p. 206øC. and one of the carboxyls. In the lac complex shellolic acid probably exists both as the lactone, and also as part of the polyester systems involving both car- boxyls and the secondary and primary hydroxyls, linked through aleuritic, ker- rolic and butolic acids with other shellolic acid molecules. Even assuming quite extensive poly- ester fk)rmation, there still remain in the shellac complex sufficient free hydroxyl and carboxyl groups to account for its adherent and coherent proper- ties. These polar groups and the arrangement of CH2 groups in sets of seven may account for the control obtained in setting hair with shellac. Table 2 relates to aleuritic, kerrolic and butolic acids. These three acids, it will be noted, are all hydroxy fatty acids of fairly low melting point. It is also interesting to note that all four of the known acids in shellac have 15- or 16-carbon skeletons. Erythrolaccin is the yellow coloring matter found in shellac. Its structure was elucidated in 1959 by Yates (18). He found it to be 1,2,5,7- tetrahydroxy-3-methyl-anthraquinone. It is therefore not susceptible to sodium hypochlorite, which is employed in bleaching shellac. It can be decolorized with sodium hydrosulfite, and work is going forward in our own laboratories toward this end.

PHYSICAl, AND CHEMICAL PROI'ERTIES OI,' SHEI.LAC 319 TAm. F. 2.--HYD•ox¾ FA,rrr¾ Acxt)s ISOL•TV.D WOnt •4leuritic •tcid: m.p. 100 101 øC. HOCH.,(CH=) sCHOH--CHOH(CH=),COOH Butolic ztcid: m.p. 54-55øC. C•4H=s(OH) (COOH) Kerrolic •lcid: m.p. 132øC. CHa(CHs)v,(CHOHhCOOH l•accaic acid, the red coloring matter of shellac, is completely destroyed by sodium hypochlorite, and therefore offers no problem in bleaching shellac to a very pale color. Its structure is so far undetermined. The hydroxyl groups of shellac, as mentioned before, play an important role in its chemistry and technology. This is particularly true of the vicihal 9,10-hydroxy groups of aleuritic acid. For example, they may be easily chelated with acetone, as shown in Fig. 2. The series of reactions shown proceeds at room temperature. In this case, acetone chelation was employed to protect the vicihal hydroxyls during the oxidation of aleuritic ackt to the corresponding di-acid (19). In bleaching shellac, too vigorous treatment with sodium hypochlorite can bring about cleavage at the 9,10 position. The practical result is a soft bleached shellac, coupled with formation of water-soluble aldehydo acids, which cannot be recovered. Borax dispersions are widely used in industry, as cosmetic chemists are aware. Borax, in addition to neutralizing the acid groups, undoubtedly combines, through the boric acid oeormed from hydrolysis of borax, with the vicihal hydroxyl groups. This type of reaction, shown in Fig. 3, is similar to that which occurs between boric acid and mannitol (20), resulting in a complexed acid stronger than boric. Aleuritic acid H()CHs(CHs)t, CHOH--CHOH(CH,2) 7COOH acetone ) --H.20 H()CH• -R CH- - -CH--R' C(X)H (acetal) 0 O CH• C--CH:• H()()C-R CH---CH R • C(X)H I I • :•o • O O -- -• CH:•--C CH:• HOOC R--CHOH--CHOH- R'--COOH 9,10-dihydroxyhexadecane-l,16-dicarboxylic acid Figure 2.--Chelation of aleuritic acid with acetone.