Kombination und disproportionierung von modellradikalen für die wachsende polystyrolkette

The mechanism of the bimolecular reaction between the model radicals for polystyryl: 1-phenylethyl, 1-phenylpropyl, and 1,3-diphenylpropyl radical is investigated by means of gas chromatography. The radicals are generated either at 80°C by thermal or at 20°C by photochemical decomposition of the corresponding azoalkanes in benzene solution. At 80°C 7,5% of the 1-phenylethyl radicals, 12,9% of the 1-phenylpropyl radicals, and 13,5% of the 1,3-diphenylpropyl radicals undergo disproportionation. Since the structure of these model radicals approaches that of the growing polystyrene chain in this order one may expect polystyryl radicals to disproportionate to about the same extent as 1,3-diphenylpropyl radicals. In photolysis experiments evidence for ortho coupling of 1-phenylalkyl radicals is found. Photoisomerisation of this ortho coupling product leads to the formation of a small amount of a thermally stable unsymmetrical dimer.     

Nutzung von Gen5 und Gen6 ts-Mutanten des Phagen T3 für die Anzeige von Hemmstoffen der DNS-Synthese

In an enzyme-specific drug screening system nalidixic acid and 3'FTdR, inhibitors of DNA synthesis, both reduce the growth of wild type and temperature-sensitive point mutants of phage T3 with different efficiencies. The wild type shows the strongest sensitivity against the drugs, while an exonuclease mutant is the most insensitive variant. The DNA polymerase mutants exhibit an intermediate degree of inhibition. The anthracycline antibiotics violamycin BI and adriblastin which preferentially inhibit RNA synthesis show the same degree of inhibition for all mutants. This is true also for the RNA synthesis inhibitor lambdamycin, which is identical with chartreusin. The protein synthesis inhibitors chloramphenicol and o-phenanthroline, a chelating agent, impair all mutants to the same extent. Our data confirm the hypothesis that structural variants of essential viral enzymes, when compared with the wild type should sensitivities against specific inhibitors and show that this T3 system could be used for the indication of specific inhibitors of DNA synthesis.     

Über die bildung und struktur von polymeren des α-cyanstyrols und des p-phenylendiacrylnitrils. II

By the reaction of p-phenylendiacetonitrile with formaldehyde in presence of alkali compounds crosslinked polymers were formed. The reaction of phenylacetonitrile with formaldehyde and reactions with model compounds indicated that these crosslinked polymers arise from phenylenacrylonitrile units by anionic polymerisation. Methoxy-hydroxymethyl. and imidoester endgroups were found to be present in the polymers. An equilibrium exists between hydroxymethyl endgroups and free formaldehyde as well as between final cyano groups and imidoester groups. Imidoester groups are shown to be formed only at cyano groups linked to hydrogen-substituted carbon atoms.     

Nachweis einer Fructokinase und ihre Bedeutung für den Stoffwechsel von Pseudomonas syringae pv. phaseolicola

The plant pathogenic Pseudomonas syringae pv. phaseolicola possesses a fructokinase which is epigenetically regulated. The k_M values for fructose and ATP are 0.56 and 0.53 mM, respectively. About 23% of the activity observed with ATP was obtained with equimolar amounts of ITP. CTP, GTP, UTP, PEP and acetl-P were ineffective, Fructokinase is responsible for the conversion of fructose to fructose-6-phosphate. In this way,. fructose, which is formed intracellulary during the growth in a sucrose or mannose containing medium, can be metabvolized via fructose-6-phosphate.     

In vitro-Einbau von 14C-Hexose-6-phosphat in Mannan, β-Glucan und Glycogen bei Candida spec. H und ihren Mutanten

Mannose-6-p is an activator of the 14C-mannose incorporation from GDP-¹⁴C-mannose in the mono- and oligosaccharides and in the mannopolymers of the cell wall proteophosphomannan produced by the food protein yeast Candida spec. H. Moreover, mannose-6-p is a precursor of proteophosphomannan: ¹⁴C-Mannose-6-p has been incorporated in absense of GTP. Corresponding behaviour shows glucose-6-p by synthesis of β-glucan and glycogen. Mutants of Candida spec. H with different efficiency in the biosynthesis of mannan, β-glucan and glycogen incorporate hexose-6-p in a different extent.     

Zur polymerisation und copolymerisation von α-methoxystyrol

α-Methoxysyrene cannot be homopolymerised, neither by an anionic nor by a cationic or free radical mecanism. This monomer is more reactive in the cationic copolymerisation than vinyl ethyl ether. Its incapability to form longer sequences indicates a low ceiling temperature. In the free radical copolymerisation with styrene, acrylonitrile, methacrylate and methyl methacrylate (MMA) the parameter for α-methoxystyrene is always found to be zero. From the parameters of the first three comonomers the Q-and e-values are estimated to Q = 0.65 and e = -1.20. The relatively low Q-value and very low reactivity towards poly (MMA radicals) demonstrate the occurance of considerable steric hindrance during polymerisations with α-methoxystyrene.     

Elektron-Donator-Akzeptor-Komplexe und Polymerisation. I. Über die Copolymerisation von Maleinsäureanhydrid mit β-Isopropenylnaphthalin

Copolymers with alternating monomer sequence are obtained by radical polymerization of a mixture containing maleic acid anhydride and β-isopropenyl naphthaline in toluene as solvent, initiated by AIBN. The composition of the copolymers is independent of the monomer feed ratio and always 1 : 1. Since the UV-spectrum shows an electron donor acceptor complex of a 1 : 1 composition and since the rate of polymerization increases with increasing complex concentration, it is concluded that the electron donor acceptor complex is the active species in the polymerization reaction.     

Copolymerisation von Acrylnitril und α-Chloracrylsäuremethylester

The kinetics of the emulsion copolymerization of acrylonitrile and methyl α-chloro-acrylate were studied. Conversion, intrinsic viscosity, density, differential composition of the products and induction period were determined. Probability functions for the distribution of acrylonitrile and methyl α-chloro-acrylate chain segments were calculated. Macromolecules from these two monomers were shown to consist of randomly arranged short chain segments. It was shown that the degree of conversion is directly proportional to the square root of the concentration of methyl α-chloro-acrylate. The induction period decreases as the methyl α-chloro-acrylate concentration increases. The degree of conversion depends on the pH of the reaction medium. At a pH > 7 the reaction is markedly restrained.     

Zur anionischen copolymerisation von α-methylstyrol und styrol

The reactivity ratios for anionic copolymerization of α-methylstyrene (M₁) and styrene (M₂) were determined. The reactions were carried out in tetrahydrofuran solutions of varied monomer contents. The polymerization stops after complete styrene consumption since α-methylstyrene does not homopolymerize under the choosen conditions. From the residual monomer contents the reactivity ratios can be computed by means of the integrated copolymerization equation, yielding r₁ = 0.015, r₂ = 17 (25°C); r₁ = 0.024, r₂ = 28 (0°C); r₁ = 0.029, r₂ = 43 (?20°C). Due to the large difference of the r-values, the monomer ratio is considerably shifted during copolymerization. Therefore, all polymer molecules, since growing over the whole conversion range, show identical structure but a shift of composition along the chain. For this phenomenon the term “second order chemical heterogeneity” is suggested.     

Zur copolymerisation von α-methylstyrol und butadien III. Das NMR-spektrum der sequenzen mit zentraler α-methylstyroleinheit

220 MHz proton resonance spectra of copolymers from α-methylstyrene and butadiene have been investigated. Model compounds have been prepared by a lithiumbutyl initiated copolymerisation in tetrahydrofurane at ?75°C. The NMR spectra of the phenyl and α-methyl group are interpreted by signals from configurational and compositional triads with a central χ-methylstyrene unit. The chemical shift of the triads, possessing a central α-methyl styrene unit, takes place to lower field in the α-methyl region to such an extend that no strong overlapping with the signals of the configurational triads takes place. In the region of the phenyl protons configurational and compositional triads are overlapping each other. Using 3,4,5-trideuterio-α-methylstyrene it is possible to assign configurational and compositional triads in the resonance spectrum of the ortho-phenylprotons.     

Untersuchungen über die anionische polymerisation. III. Über die anionische copolymerisation von α-cyansorbinsäurebutylester, 2-nitrobuten-(1), acrylonitril und atropanitril

In the anionic copolymerization of α-cyanosorbinic acid butylester with 2-nitrobutene-(1) in DMF as solvent the anion of initiator, the counter ion and the temperature of reaction showed no marked influence on the copolymerization parameters. Different r values and yields were found in varying the solvent (THF, benzene, DMF). No copolymers were obtained by polymerization of the monomer pairs α-cyanosorbinic acid butylester-α-cyanostyrene and α-cyanostyrene-acrylonitrile with NaCN in DMF.     

Zur Copolymerisation von α-Methylstyrol und Butadien. IV. Die s0/M-Beziehung der Copolymeren

The sedimentation constants of poly-α-methylstyrene, polybutadiene and their copolymers have been measured in cyclohexane at 37°C. Depending on their composition block and random copolymers show the same sedimentation behavior. Within experimental error no influence of the sequence length distribution of the comonomers exists. The sedimentation constants of the copolymers may be calculated from the s₀/M-relations of the homopolymers.     

Über die Synthese und das Redoxverhalten einiger Modellsubstanzen für polymere Hydrochinon-Chinon-Redoxsysteme. V1

Some new model compounds for hydroquinone-quinone redox polymers were prepared, consisting of two hydroquinone nuclei which are linked by a methylene, ethylene or trimethylene group. Their redox characteristics were investigated by potentiometic titration. The titration curves were interpreted.     

Kuhn-Mark-Houwink-Sakurada-Beziehung für poly(ϵ-caprolactam)

The Kuhn-Mark-Houwink-Sakurada relationship for poly(?-caprolactam), (polyamide 6), is established, based on the absolute determination of the weight-average molecular weight by light scattering. It is obtained ([η] in cm³.g^?1): The unperturbed dimensions of this polymer in both solvents are also determined by using the Stockmayer-Fixman method.     

Zur copolymerisation von ethylen und α-olefinen mit ziegler-katalysatoren

Starting with four reaction equations which are at least necessary to describe the copolymerization of two monomers, equations for the kinetics and the molecular weight regulation with and without hydrogen are derived. The equations are used to evaluate the results of the copolymerization of ethylene and 1-butene. The numerical values of the reactivity ratios r differ by approximately 3 orders of magnitude, but do not depend on whether the molecular weight is regulated by hydrogen or not. The rate of polymerization is scarcely influenced even by great amounts of 1-butene. It depends nearly completely on the concentration of ethylene. On the other hand the comonomer enormously influences the average molecular weight of the copolymer. This influence increases with hydrogen content.     

Polymerization of α,α-disubstituted β-propiolactones and lactams, 12. Properties and crystalline structure of poly(β-propiolactam)s

A series of α,α-disubstituted β-propiolactams (substituted nylon 3 polymers) was prepared from non-optically active lactams. Their thermal characteristics, densities, and x-ray fiber diffraction patterns were recorded. One of the α-substituents was always a methyl group while the other was either CH₃, C₂H₅, n-C₃H₇, or n-C₄H₉. The melting point for the dimethyl substituted polymer was 268°C; the others were respectively 76, 74, and 72°C. X-ray fiber diffraction data on all four samples yielded the same fiber repeat of ≈8,4 Å. A minimum energy based conformational analysis for the α,α-dimethyl derivative indicates that two conformations correspond to this repeat, each of which is a 2₁ helix.     

Kinetik der radikalischen copolymerisation α-substituierter styrole mit styrol. 1. Teil. Copolymerisation von α-methylstyrol mit styrol oberhalb der ceiling-temperatur von α-methylstyrol

The radical copolymerization of α-methylstyrene with styrene in the temperature range from 60 to 150°C can be described according to the equations derived by WITTMER with the assumption, that the addition steps of α-methylstyrene may be reversibel. For the temperature range from 60 to 110°C it could be demonstrated that it would be sufficient to consider only the reversibility of the addition steps of α-methylstyrene to a radical end with α-methylstyrene as the terminal unit. At a reaction temperature of 150°C the addition of α-methylstyrene to a styryl chain end is also reversible, the equilibrium constant being only 1/30 of the α-methylstyrene homopolymerization. The retardation of the polymerization rate by admixture of small amounts of α-methylstyrene to styrene was measured. The results allow an estimation of the rate constants and activation energies of the chain propagation and depolymerization steps.     

Modelle und modellreaktionen für die halogenierung von cis- und trans-1.4-polybutadien. Ein beitrag zur stereochemie der „kopf-kopf-polyvinylhalogenide”︁

The all-cis and all-trans isomers of have been synthesized in order to investigate reaction models for cis- and trans-1.4-polybutadienes. The halogenation by means of pyridinium perbromide and pyridinium perchloride leads to these being model compounds for head-to-head poly(vinyl halides). Structural units with erythro configuration result from trans olefins, such with threo configuration from cis olefins. The characteristic C? X frequencies for trans and gauche positions of vicinal halogen atoms derived from infrared and RAMAN spectra are being determined: trans position ν_{C? Br} 550 to 560 cm^?1 (IR), 595–620 cm^?1 (Ra), ν_{C? Cl} 650–660 cm^?1 (IR), 670–690 cm^?1 (Ra), gauche position ν_{C? Br} 520–535 cm^?1 (IR, Ra), ν_{C? Cl} 550–560 cm^?1 and 590–610 cm^?1 (IR, Ra). On the basis of these values a local conformational analysis of the halogenated cis- and trans-1.4-polybutadienes has been made.