STRUCTURAL I'ACTORS IN POLVM I.RI/.ATION 59 



arsenic/antimony and carbon were most active as inhibitors; cadmium, aluminum, 

 sulfur, silicon, tellurium, lead, tantalum and gold were among the inactive 

 elements tested. Efforts toward relating physical and chemical properties to 

 catalytic activity were for the most part unsuccessful, but some degree of correla- 

 tion was obtained for hardness, specific gravity and electrical resistivity. In addi- 

 tion, it was observed that virtually all elements increasing oxidation rate occurred 

 in Periodic Groups I, II, VI, \'I1 and VIII (ist transition — Fe, Co, Ni) whereas 

 those inhibiting oxidation fell into CJroups III, IV and V. 



During the study of Fe(III)-biopolymer models and the first of the investiga- 

 tions with elementary surfaces, it was assumed that the product of pyrogallol 

 oxidation was in all cases identical with the product formed by the action of per- 

 oxidase, the benztropolone, purpurogallin. When the ultraviolet spectra of prod- 

 ucts formed in various systems were determined, however, the characteristic two 

 maxima of purpurogallin (in the regions of 270 and 315 /x, the exact position 

 depending upon solvent) were almost consistently lacking. Among all systems 

 with biopolymers or pure elements, the only exceptions were cobalt and man- 

 ganese, whose products yielded a strong purpurogallin spectrum. More extensive 

 study of the autoxidation of pyrogallol confirmed the absence of this specific reac- 

 tion product, or its presence only in trace amounts (36). Various modes of oxida- 

 tion — anodic, hypochlorite, peroxidic — all yielded highly polymerized, brown to 

 black products, insoluble in purpurogallin solvents, devoid of its spectral features, 

 and yielding, on analysis, hydrogen contents of 2-3% (pyrogallol, 4.75 /t; Pur- 

 purogallin, 4.5%). The products of cobalt and manganese catalysis yielded hydro- 

 gen contents of 4.3-4.5 per cent, values close to those for purpurogallin. 



The peroxidase-mimicking metal catalysts exhibited stereospecificity only in 

 sufficiently polar reaction media, water, and methanol. In the homologous alcohol 

 series, from methanol to octanol, the distinguishing second ultraviolet maximum 

 of purpurogallin becomes reduced to an absorption shoulder (Co), progressively 

 weaker inflections (Co-C,,), and finally disappears (C,s). 



A study of the catalytic properties of oxides (of Al, As, Cu, Mg, Mn, Hg, Si 

 and Zn) in aqueous media, and of various salts (mainly the phosphates, halides, 

 sulfates, and carbonates of Groups la and Ila) in ethanol and chloroform dem- 

 onstrated a number of catalytic properties of interest, including u) the great 

 catalytic efficiency of silica gel, but the complete inactivity of powdered quartz; 

 b) the sometimes opposed activities of metals and their oxides; and r) the stereo- 

 specific (purpurogallin-synthesizing) activity restricted to lithium halides and 

 carbonates among the simple compounds tested. 



Turning once again to the more complex silicates, stereospecificity was lacking 

 in all cases save for glass fiber, which catalyzed purpurogallin synthesis in non- 

 aqueous media. 



The investigation of model systems and matrix activity has thus taken a new 

 turn toward the study of enzyme-mimicking models. The matrix concept as it has 



