Zur synthese von siloxanen: IV. Acetolyse der konfigurationsisomere des 1-chlor-1,3,5-trimethyl-3,5-bis(trimethylsiloxy)cyclotrisiloxans

Abstract

The acetolysis reaction of 1-chloro-1,3,5-trimethyl-3,5-bis(trimethylsiloxy)cyclotrisiloxane was investigated using 29Si NMR spectroscopy. The three possible configurational isomers, formed in the synthesis, could not be separated. Taking into account the concentration of the three isomers in the mixture, the rate of their acetolysis reactions, the position and the order of the 29Si NMR signals of the chloro- and acetoxycyclotrisiloxane isomers from one set of 29Si NMR data information was obtained on the configuration of the isomers assigned to the NMR signals, the rate constants of the three isomers, and the stereochemistry of the acetolysis reaction. We found that the isomer present in the lowest concentration, showing the largest high field shift and the lowest reactivity has the all- cis configuration, and that the acetolysis reaction proceeds with retention of configuration.