Die Titration von Sauerstoff und Antioxydantien mittels freier 2,4,6-Tri-tert.-butylphenoxy-Radikale

Ohne Zusammenfassung     

Das Verhalten des 2,4,6-Tri-tert.butylphenyllithiums gegenüber Halogensilanen. Bildung und Umwandlung des Trichlorsilyllithiums,LiSiCl3

The Behaviour of 2,4,6-Tri-tert.butylphenyllithium towards Halosilanes. Formation and Conversion of Trichlorosilyllithium, LiSiCl₃ Trichlorosilyllithium, LiSiCl₃ 2 , is formed as the result of a fast metal halogen exchange reaction at ?78°C in THF between 2,4,6-tri-tert.butylphenyllithium 1 or mesityllithium and bromotrichlorosilane. Also the interaction of 1 with trichlorosilane gives 2 after partial deprotonation of HSiCl₃. 2 is not isolated; it's existence in the THF solution is proved by protonation or deuteration, resp., and by identification of the HSiCl₃ or DSiCl₃ formed that way by means of ¹H-NMR or infrared spectroscopy. Attempts to react 2 with various electrophiles failed; also efforts to trapp dichlorosilylene, the expected decomposition product of 2 , by isoprene, were unsuccessful. Studies of the thermal decomposition of LiSiCl₃–THF solutions led to the identification of polychloropolysilanes and of insertion products of SiCl₂ in tetrahydrofuran.     

Silane pyrolysis

We show that silane pyrolysis is initiated by decomposition on the amorphous silicon surface, with an activation energy E_a of 56 kcal/mole. The observed surface decomposition rate is only weakly dependent on silane pressure. Much faster delayed decomposition rates, approximately independent of surface area and proportional to pressure, are shown to be initiated by surface reactons. A model for surface decomposition is given. Also a model for gas reactions is suggested based on H atom or SiH₃ release by surface decomposition, causing chain reactions that process the gas to higher silanes that decompose rapidly. This model can explain the previous observations that the initial disilane formation rate and the delayed decomposition rate were independent of the surface area to volume ratio A/V, which had misled previous investigators to suggest homogeneous initiation processes.     

Silane. XII. Alkalische Solvolyse von substituierten Benzylsilanen

Alcaline solvolysis of substituted phenyl and benzyl silanes listed in “Inhaltsübersicht” is compared. The inductive transfer coefficient of the CH₂ group is fixed.     

Silane. XI. Substituenten-Effekte von C- und Si-haltigen Gruppen

Substituent effects of the groups (CH₃)₃C-, (CH₃)₃Si- and CF₃- (in m- and p-position) were investigated by alkaline solvolysis of (X-C₆H₄)_n(CH₃)_3–nSiH in ethanol/water solutions. The additivity rule was verified.     

环氧硅烷室温交联丙烯酸酯共聚无皂水溶胶的研究 Ⅰ.环氧硅氧烷微乳液的制备

环氧硅烷室温交联丙烯酸酯共聚无皂水溶胶的研究 Ⅰ.环氧硅氧烷微乳液的制备     

2,4,6-Trichloropyrimidine. Reaction with sodium amide

The first reaction between 2,4,6-trichloropyrimidine 1 and anionic nitrogen nucleophiles is described. Treatment of 1 with one equivalent of sodium amide gave mixtures of 4-amino-2,6-dichloropyrimidine 2 and 2-amino-4,6-dichloropyrimidine 3 . Additional quantities of sodium amide failed to provide either diamino- or triaminopyrimidines. Instead, the strongly basic nature of sodium amide led to higher molecular products that were not characterized.     

2,4,6-Trinitrotoluol

Ohne Zusammenfassung     

2,4,6-trichloropyrimidine. Reaction with ethanolamine and diethanolamine

2,4,6-Trichloropyrimidine, 1, reacts with neutral nucleophiles, such as ethanolamine and diethanolamine, to produce both mono- and disubstituted derivatives resulting from replacement of either one (2 and 3) or two (4) chlorine atoms. The third chlorine could not be replaced by these nucleophiles. Failure of this final step was attributed to intramolecular hydrogen bonding of the nucleophiles.     

Polymorphism in 2,4,6-trinitrotoluene crystallized from solution.

An examination has been made of the role of solvent type in the definition of the polymorphic nature of 2,4,6-trinitrotoluene precipitated from solution. A combination of calorimetric and structural techniques including in situ crystallization studies using synchrotron radiation has shown that the variations in polymorphic form following precipitation from solution do not arise specifically from any stereospecific guidance that the nature of the solvent might impose on the structural form. Rather the differences are linked to the variations in solubility and hence supersaturation which might build up prior to nucleation and growth and to the isolation of the metastable orthorhombic phase from the solvent. The final conclusion is that the changes fit well with Ostwald's Law of Stages with the orthorhombic form always precipitating initially followed by its conversion to the stable monoclinic form. The previously observed tendency for some solvents to yield one or the other form then becomes attributable to kinetics in solution rather than structural control. It can be associated with the solubility of the material in the solvent used and the role of this factor in a solvent-mediated phase transformation. On this basis rules can be formulated for the isolation of the metastable forms of this and similarly related polymorphic systems.