In continuation of previous kinetic work on the hydrolytic polymerization of εcaprolactam (CL) (Part I–III) in which evidence was obtained that all the predominant reactions are catalyzed by endgroups, special experiments were undertaken in order to study the specific role played by the NH2 and COOH endgroups. To that end kinetic runs at 221°C. were performed with Cl‐water systems (containing 5–7 mole‐% of water) in which the symmetry of the concentrations of NH2 and COOH groups was disturbed by the addition of about 1 mole‐% of either an amine or a carboxylic acid [hexamethylenediamine (HMD), adipic acid (ADA), and sebacic acid (SBA) were used]. The concentrations of unconverted lactam and of amino and carboxyl groups were determined as previously described; special techniques were worked out for the determination of the small concentrations of unconverted HMD, ADA, and SBA. The main observations are: (1) added HMD disappears much more rapidly from the reaction mixture than added ADA or SBA; (2) the dicarboxylic acids have considerable accelerating effect on the formation of endgroups. Only a general qualitative discussion of these results is given. The principal deductions may be summarized as follows. (a) The initial reaction of the polymerization process, the hydrolysis of CL, is found to be catalyzed by COOH groups. (b) The main contribution to the increase in chain length is furnished by the addition of CL to NH2 endgroups exclusively (aminolysis of the lactam molecule). (c) This addition reaction is catalyzed by COOH groups. (d) Probably, the polycondensation reaction of NH2 and COOH groups is also catalyzed by COOH groups.

In this first‐paper of a series of publications on the mechanism of the polymerization of ϵ‐caprolactam (CL), an investigation of the kinetics of the polymerization initiated by ϵ‐aminocaproic acid (ACA) is reported. Experiments were performed at 254°C. for three different initial ratios (ACA/CL)0:0.05, 0.022, and 0.011 mole/mole. The concentration (x) of unconverted CL and that of end groups (c) were determined by extraction with water at room temperature and by potentiometric titration, respectively. The method of kinetic evaluation consists in the direct checking of rate equations making use of the quantities dx/dt and dc/dt which were determined graphically from the curves of x and c versus time. In this way tedious integration procedures are avoided and the testing of rather different mechanisms is much easier. Moreover, it is not necessary to make the assumption of constant rate coefficients which, of course, will seldom apply. Thus the inadequacy of the “polycondensation mechanism” has been proved for every time instant separately, although accidentally the rate constant of the main reaction is fairly constant. In this polycondensation mechanism it is assumed that polymer formation can take place only by polycondensation of ACA, the supply of which is provided for by the reaction of CL with water formed in the process of polycondensation. It turns out that even when the rate of hydrolysis of CL is so high that the polycondensation reaction is rate determining, this latter rate is to small by a factor of 10 or more to account for the rate of CL conversion observed. It is shown that this difficulty can be overcome only by incorporating a third reaction in the mechanism, a reaction which must provide for the main consumption of CL. We have assumed this reaction to be a reversible polyaddition reaction, i.e., a reaction in which CL is added to one of the end groups of the polymer molecules. The rate constant for this reaction derived from the experiments appears to be in good agreement with the value derived from the experiments on the polymerization of CL initiated with water.

Ersetzt man in der Formel eines Purin-Derivats eines oder mehrcrc der Stickstoffatome des Ringsystems durch Methingruppen, so gelangt man zu Strukturtypen. fur die sich durch Verwendung des Praefix ,.Dcs-aza-" einfache BezeichnLngen ableiten lassen. W i r haben uns die Aufgabe gcstcllt. derartige Verbindungen zu synthetisieren und zu prufen ob und inwiefernc sie als Hemmstoff,? physiologischer Prozesse wirksam sind.Die vorliegende Mitteilung beschiiftigt sich mit der Synthese von I-Desaza-adenin. dem von einem Imidazopyridin abgeleiteten Analogen dcs Adenins. Seine 13arstellung hatte die Synthese des bisher ebenfalls unbekannten 2,3.4-Triamino-pyridins zur Voraussetzung.

Some experiments are described which show that the polymerization of ϵ‐caprolactam (CL) can be accomplished by heating the lactam under anhydrous conditions in the presence of hydrogen chloride or of salts of strong acids and ammonia or amines at temperatures of 220–260°C. To study this type of polymerization more closely, two series of kinetic experiments with the sytem CL–HCl hae been performed (254°C.; initial molar ratios of HCl to CL, 0.025 and 0.0125). The progress of the reaction, characterized by the degree of conversion (determined by extraction of the unconverted lactam with water), is compared with the polymerization of CL initiated by corresponding amounts of water or of ϵ‐aminocaproic acid. The products obtained have been characterized by endgroup titration values and intrinsic viscosity. Some additional data have been obtained by chromatography and IR investigations. The titrations show that the molecules bear an amino group at one end of the chain; the nature of the other endgroup is still obscure. Reaction constants calculated for an uncatalyzed additon of CL to amino groups prove to be of about the same magnitude as those of the water‐initiated polymerization without additional HCl. At the same time some kinetic experiments with the system CLH2OHCl are presented. Both systems have some striking features in common. The catalytic effect of the HCl present in this system can be attributed to the rapid formation of amino groups in the very first moments of the reaction, thus leading to an enhanced rate of polymerization by addition of CL to amino groups.