Polycondensation and disproportionation of an oligosiloxanol in the presence of a superbase
摘要:
Kinetics of reactions of model oligosiloxanols, 1,1,3,3,3-pentamethyldisiloxane-1-ol (MDH) and 1,1,3,3,5,5,5-heptamethyltrisiloxane-1-ol (MD2H), which occur in the presence of phosphazenium superbase, hexapyrrolidine-diphosphazenium hydroxide, in an acid-base inert solvent, toluene, was studied using sampling and gas chromatographic analysis method. In addition, kinetics of reactions of MDH and MD2H with trimethylsilanol (MH) was studied. In the MDH and MD2H systems the oligosiloxanol condensation competes with the oligosiloxanol disproportionation, the latter being the dominating process. The disproportionation products, i.e. MDn + 1H and MDn - 1H, n = 1, 2,... undergo analogous consecutive disproportionation and condensation reactions. The kinetic law was derived and rate parameters determined from initial rates and by computer simulation to the best agreement with experimental data. Both competing reactions, the disproportionation and the condensation, conform to the same general kinetic law being first internal order in substrate and first order in catalyst. Activation parameters of these reactions were determined. The results were interpreted in terms of a bimolecular mechanism in which nucleophilic attack of the silanolate anion directed to silicon of the silanol group causes the cleavage of one of its geminal bonds to oxygen, either the one to hydroxyl leading to condensation or the one to siloxane which leads to disproportionation. The latter is faster as the silanolate is a better leaving group compared with OH-. Moreover, in the pentacoordinate silicon transition state (or intermediate) the siloxane substituent preferentially enters the apical position, thus driving the OH substituent into the unreactive equatorial position. (C) 2002 Elsevier Science B.V. All rights reserved.
[DE] VERFAHREN ZUR HERSTELLUNG VON FLUOR ENTHALTENDEN VERBINDUNGEN ÜBER FLUOR-HALOGENAUSTAUSCH DURCH SPEZIELLE POLYAMINOPHOSPHAZEN-KATALYSATOREN [EN] METHOD FOR PRODUCING A COMPOUND CONTAINING FLUORINE VIA FLUORINE-HALOGEN EXCHANGE BY SPECIAL POLYAMINO PHOSPHAZENE CATALYSTS [FR] PROCEDE DE FABRICATION DE COMPOSES CONTENANT DU FLUOR PAR ECHANGE FLUOR-HALOGENE A L'AIDE DE CATALYSEURS POLYAMINOPHOSPHASES SPECIFIQUES
摘要:
含氟化合物的硬化方法,通过将含有可与氟交换的卤素的化合物与一种氟化物或氟化物混合物按照下式(I)的普遍公式进行反应来实现,MeF (I),其中对于一种碱土金属离子,NH4+ 离子或碱金属离子,以及存在或不存在溶剂的情况下,在60至260°C的温度下进行,其特征在于在一种化合物或化合物组合物的存在下进行反应,该化合物或化合物组合物具有下式(IIa)和/或(IIb)的普遍公式。公式II a 公式II b 公式II c,其中X1和/或X2和/或X3独立地具有下式(IIc)的基团或与权利要求中提及的其他基团相对应。
[DE] PHOSPHAZENIUMSALZ-MISCHUNGEN ENTHALTEND HEXAKIS(AMINO)DIPHOSPHAZENIUM, TETRAKIS(AMINO)-PHOSPHONIUM UND POLYAMINOPHOSPAZENIUM-SALZE<br/>[EN] PHOSPHAZENIUM SALT MIXTURES CONTAINING HEXAKIS(AMINO)DIPHOSPHAZENIUM, TETRAKIS(AMINO)-PHOSPHONIUM AND POLYAMINOPHOSPAZENIUM SALTS<br/>[FR] MELANGES DE SELS DE PHOSPHAZENIUM CONTENANT DES SELS D'HEXAKIS(AMINO)DIPHOSPHAZENIUM, DE TETRAKIS(AMINO)PHOSPHONIUM ET DE POLYAMINOPHOSPHAZENIUM