A systematic approach is suggested to design chemical systems capable of displaying stationary, symmetry-breaking reaction diffusion patterns (Turing structures). The technique utilizes the fact that reversible complexation of an activator species to form an unreactive, immobile complex reduces the effective diffusion constant of the activator, thereby facilitating the development of Turing patterns. The chlorine dioxide/iodine/malonic acid reaction is examined as an example, and it is suggested that a similar phenomenon may occur in some biological pattern formation processes.

The chlorite-iodide reaction is unusual because it is substrate-inhibited and autocatalytic. Because analytically pure ClO2 - ion is not easily prepared, it was generated in situ from the rapid reaction between ClO2 and I-. The resulting overall reaction is multiphasic, consisting of four separable parts. Sequentially, beginning with mixing, these parts are the (a) chlorine dioxide-iodide, (b) chlorine(III)-iodide, (c) chlorine(III)-iodine, and (d) hypoiodous and iodous acid disproportionation reactions. The overall reaction has been studied experimentally and by computer simulation by breaking it down into a set of kinetically active subsystems and three rapidly established equilibria:  protonations of chlorite and HOI and formation of I3 -. The subsystems whose kinetics and stoichiometries were experimentally measured, remeasured, or which were previously experimentally measured include oxidation of iodine(−1,0,+1,+3) by chlorine(0,+1,+3), oxidation of I- by HIO2, and disproportionation of HOI and HIO2. The final mechanism and rate constants of the overall reaction and of its subsystems were determined by sensitivity analysis and parameter fitting of differential equation systems. Rate constants determined for simpler reactions were fixed in the more complex systems. A 13-step model with the three above-mentioned rapid equilibria fits the overall reaction and all of its subsystems over the range [I-]0 < 10-3 M, [ClO2 -]0 < 10-3 M, [I-]0/[ClO2 -]0 = 3−5, pH = 1−3.5, and 25 °C. The derived model with all experimentally determined rate and equilibrium constants fits both the overall reaction and all of its subsystems within 1% relative accuracy.

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e.g. in nitro compounds 1741 or conjugated acids r67al.Finally the phenomenon of optical activity induced by a magnetic field has presented the spectroscopist with a new aid for the determination of energy levels, particularly in inorganic compounds 1751 sensitive instruments and those which can be used further into the UV range.I am grateful to the Deutsche Forschungsgemeinschaft for their financial support. Furthermore, these investigations would have been impossible without the conscientious work of our technical assistants and the supply of' interesting samples by many colleagues at the Institute and throughout the world. I should like to express my sincere thanks to all of them. Received: J u l y 19th. 1967 [ I. a-lactams as Possible Intermediates ; Unsuccessful Attempts at Preparation a-Lactams [aziridinones] are the first and, to date, only representatives of the three-membered ring carbonyl compounds of general structure ( I ) to have been synthesized (see Section 11).It was Leuchs"1 who first proposed a-lactams as reactive intermediates. He observed that a-amino acid N-carboxyanhydrides ("Leuchs-Anhydride") (2) rapidly lose carbon dioxide o n heating to form polypeptides ( 4 ) . Lerrchs postulat-ed an cc-lactam (3) as intermediate but it could not be isolated [21. [*] Prof. I. Lengyel 1721 (1908).[21 Leuchs' assumption that the decarboxylation of a-amino acid N-carboxy anhydrides leads to cyclic polymers, proved erroneous later: it was recognized ( R . B. Woodward and C. H. Schramm, J. Amer. chem. SOC. 69, 1551SOC. 69, (1947) that the products are linear polypeptides and not cyclic a-lactam polymers. The possibility that certain a-haloamides may cyclize to alactams on dehydrohalogenation with bases has been investigated for two aromatic precursors of this class by two groups o f workers[41. In no case could an a-lactam be isolated or detected as intermediate. The reaction of a-chloro-a,?-diphenylacetanilide (5) with sodium hydride [4b, 4c, 4f, 4g1 gave 2-(3,3-diphenyl-2-indolinon-l-yl)-2,2-diphenylacetaniIide (6) as the major product, together with smaller amounts of 3,3-diphenyl-2-indolinone (7) and 1,3-diphenyl-2-indolinone (8). The formation of all three products can be explained through a common a-lactam intermediate (9) [4c, 4f1. 131 J . C. Sheehan and P. T. Izro, J. Amer. chem. SOC. 79, 1985SOC. 79, (1948 ibid. 71, 4059 (1949).[4] a) S. Sarel and A. Creenberger, J. org. Chemistry 23, 330 (1958); b) S. Sarel If sodium hydride is replaced by sodium amide, the rearrangement of ( I I ) mainly into a-anilino-r-phenylacetamide (13) is observed [4al.(12)Interestingly, the course of the analogous reaction of (5) is fundamentally different: When a-chloro-cr,a-diphenylacetanilide (5) is treated with sodium amide in liquid ammonia, N-benzhydryl-N-phenylurea ( l S ) , or-anilino-a,a-diphenylacetamide (I6), and a-amino-cr,a-diphenylacetanilide (17), are formed in the ratio 5 : 1 : 1 [4el. (The reaction of (5) with NaH leads to (6), (7), and (8).) It has been assumed[4el that compounds ...