Mechanism of vinyl chloride polymerization

An overall mechanistic scheme for the suspension polymerization of vinyl chloride is presented. The process can be resolved into five discrete stages, each of which presents a unique environment for the interaction of the systems parameters. It is shown that the surface area of the polymer formed during the reaction is not a major factor in autoacceleration and that the increase of kinetic chain length with conversion is due to a radical dilution effect. The latter is a direct result of the difference in rates between polymerization and radical formation, the former being greater. The increase of the initial polymerization rate and the reduction of autoacceleration brought about by chain transfer agents can be explained by the lower diffusion rate and greater bulkiness of the chain transfer agent radical relative to that of the monomer radical. The chaintransfer agent CBr₄ is preferentially absorbed by PVC from solution in vinyl chloride. With lauryl peroxide as initiator it is shown that the “hot spot” is the result of a build-up of initiator in the monomer caused by its exclusion from the polymer phase. Vinyl chloride was found to dissolve 0.03% PVC at ambient temperature and to have no effect on the decomposition rate of lauryl peroxide.     

Conformations of luteoskyrin and rugulosin in solution

The pigments Luteoskyrin (Ls) and Rugulosin (Rg) might adopt a priori two extreme conformations, a planar and an angular one. To determine the predominant conformation in solution, the nature of the lowest energy transition of the chromophores and the presence of intramolecular H-bonding have been investigated. The solvent effects on electronic absorption and CD spectra indicated the π-π* nature of the lowest energy transition. Treatments of the electronic absorption results according to McRae and Kosower relations, IR absorption and PMR spectra suggested the presence of strong intra-molecular H-bonds. From these results it was concluded that Ls and Rg adopted in a variety of solvents the most planar conformation.     

Studies on the exchange characteristics of [Co(NH3)6]3+ in amberlite IRC-50

Summary The exchange of Co(NH₃)₆]³⁺-ions on amberlite IRC-50 resin has been studied at room temperature. For this exchange process the cations are effective in the order: Cs⁺<Rb⁺<K⁺<Na⁺<Li⁺<NH₄ ⁺<Mg²⁺ <Ca²⁺<H⁺ and (C₂H₅)₄N<(CH₃)₄N⁺ ≪Cetyltrimethylammonium-ion <Cetylpyridinium-ion. The logarithm of the selectivity coefficient gives linear graphs when plotted against the radius of the hydrated ions or the reciprocals of theDebye-Hückel parameter?.     

A high resolution mass spectrometric measurement system for a vacuum fusion apparatus

A high resolution mass spectrometric read-out system for a vacuum fusion apparatus is described. Rapid analyses are possible and the rate at which various gases are evolved can be monitored. Gas mixture assays are accomplished by scanning the nominal mass 28 peak. Serial measurements of CO⁺, N₂⁺ and C₂H₄⁺ are made. Thus detection and measurement of evolved hydrocarbons are possible. The results for silver and tin from a conventional vacuum fusion apparatus and the mass spectrometer apparatus are compared.     

Zur Hemmung der katalytischen Jodwirkung auf das system Cer(IV)-sulfat—arsenige Säure

Zusammenfassung Die Hemmung der katalytischen Jodwirkung auf die Redoxreaktion Cer(IV)-sulfat—arsenige Säure wird hinsichtlich ihrer Vorund Nachteile bei analytischer Anwendung untersucht. Brucinacetat gibt mit Ceriion in schwefelsaurer Lösung nachFischl eine quantitativ auswertbare Farbreaktion. Kritische Untersuchungen hierzu ergeben, daß die Lösungen zur vollen Entwicklung und Stabilität der orangeroten Farbe (Absorptionsmaximum 470 nm) mindestens 10 bis höchstens 12 Min. auf 105° zu erhitzen sind. Die Anwendung auf die Jodbestimmung im Blutserum nachSpitzy, Reese undSkrube bietet infolge methodischer Komplizierung keinen besonderen Vorteil.

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Summary The inhibition of the catalytic action of iodine on the redox-reaction ceric sulphate—arsenious acid was investigated with regard to the advantages and disadvantages in its analytical application. Brucine acetate gives, according toFischl, a quantitative colour reaction with ceric ions in sulphuric acid. Critical investigations carried out show that the solution only develops a stable, orange-red colour (absorption maximum 470 nm) between 10 and 12 minutes heating. Application of this procedure to the determination of iodine in blood serum by the method ofSpitzy, Reese, andSkrube introduces complications and has, therefore, no special advantage.

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Résumé Etude des avantages et des inconvénients de l'emploi en chimie analytique de l'inhibition de l'effet catalytique de l'iode sur la réaction d'oxydo-réduction cerium(IV)-sulfate—acide arsenieux. Avec les ions cériques l'acétate de brucine donne, en solution sulfurique, d'aprèsFischl, une réaction colorée susceptible d'être employée pour une détermination quantitative. Des recherches critiques ont montré que les solutions devaient être chauffées pendant au moins 10 min. et au plus 12 min. à 105° pour développer complètement la couleur rouge orangé et obtenir sa stabilité (maximum d'absorption à 470 nm). L'application à la détermination de l'iode dans le sérum sanguin d'aprèsSpitzy, Reese etSkrube n'offre aucun avantage particulier du fait de la complication de la méthode.

     

Recherches sur la formation et la transformation des esters LXXIX [1]. Sur la réaction de l′isothiocyanate d′o-méthoxycarbonyl-phényle avec divers acides et l′acide sérinephosphorique

Amino acids devoid of «leaving groups» on their β carbon atom (neither ? OH: serine, nor ? SH: cysteine) react with o-methoxycarbonyl-phenyl isothiocyanate (I) in the presence of one equivalent of NaOH, in water-dioxane or in ethanol, to yield the corresponding hydroquinazolinone derivatives II which were isolated as free acids. When treated with CH₃COOH + conc. HCl the hydroquinazolinone resulting from the reaction of L -serine with I undergoes a nucleophilic attack of the carbon bearing the leaving group ? OH by a lone pair of electrons of S; this attack produces the formation of an additional thiazolidine ring, yielding the thiazoloquinazolinone derivative (?)-III. In an analogous reaction DL -serine phosphoric acid treated with I at pH 8–9 yields the corresponding substituted hydroquinazolinone which, boiled in 1N hydrochloric acid, undergoes ring closure to (±)-III by the same mechanism as the serine derivative (leaving group: ? OPO₃H₂). L -Cysteine reacted with 2 equiv. of I and then treated with CH₃COOH + conc. HCl gives two products: (?)-III produced by the same mechanism as for serine (leaving group: ? SH), and the quinazolinone derivative IV where the ? SH group is also thiocarbamoylated.     

Totalsynthese und absolute Konfiguration von natürlichem Multifloramin

The diphenol 1 was resolved into its antipodes and their absolute configuration was established. The levorotatory isomer R-(?)- 1 was oxidized to the dienone R-(?)- 6 , which was rearranged to afford natural (?)-multifloramine (R-(?)- 7 ), thus establishing that the latter has the R-configuration. By the same reaction sequences, the enantiomeric diphenol S-(+)- 1 was transformed to provide (+)-multifloramine (S-(+)- 7 ) of the S-configuration.     

Metal coordination polymers. II. Molecular weight studies of beryllium phosphinate polymers in toluene

The number-average molecular weights of beryllium 4-biphenyl(phenyl)phosphinate, di-n-pentylphosphinate, di-n-heptylphosphinate, and trifluoromethyl(phenyl)phosphinate are degraded by the presence of water in toluene. It is proposed that easily hydrolyzable P? O? P bonds contribute, in part, to the bonding of these polymers.     

A ferrocene based palladacyclic precatalyst for the Suzuki cross-coupling of aryl chlorides

Addition of palladium acetate to 2-(dicyclohexylphosphino)-phenylferrocene gave palladacycle 16 that is a very effective precatalyst for the Suzuki cross-coupling of aryl chlorides at room temperature (1 mol% 16) or 60 degrees C (> or = 0.01 mol% 16).