Trimethylsilyl Derivatives for the Study of Silicate Structures. Part 7. Calcium Silicate Structures

Article abstract of DOI:10.1039/DT9800001282

A detailed study was made of the yield and products of trimethylsilylation of calcium orthosilicate (Ca2), rankinite (Ca3), and pseudowollastonite (Ca3) under various experimantal conditions.With hexamethyldisiloxane, chlorotrimethylsilane, and isopropylalcohol as reagents, in the absence of added water Ca2 yielded predominantly SiO4(SiMe3)_x(Prⁱ)_4-x (x = 1-4) and a lesser amount of Si2O7(SiMe3)_x(Prⁱ)_6-x (x = 2-6), Ca3 gave predominantly Si2O7(SiMe3)_x(Prⁱ)_6-x (x = 2-6), and Ca3 gave predominantly Si3O9(SiMe3)_x(Prⁱ)_6-x (x = 2-6) and Si3O10(SiMe3)_x(Prⁱ)_8-x (x = 3-8).Mixed trimethylsilyl-isopropyl derivatives were converted to the fully trimethylsilylated derivatives SiO4(SiMe3)4, Si2O7(SiMe3)6, and Si3O10(SiMe3)8 on treatment with Amberlyst 15 ion-exchange resin in the presence of hexamethyldisiloxane.In the trimethylsilylation of Ca2 reaction of mineral itself is complete within ca. 6 min at room temparature, under the conditions employed, and the majority of unwanted side reactions which yield Si2O7 and Si3O10 derivatives occur during the first 3-4 min.Side reactions may be suppressed by increasing the proportion of isopropyl alcohol and decreasing that of Ca2 in the reagents.The presence of both isopropyl alcohol and chlorotrimethylsilane is necessary for reaction to occur.Isopropyl alcohol may be replaced by either ethyl alcohol or water, altough the yield is reduced.When isopropyl alcohol is replaced by water, only the fully trimethylsilylated derivatives are formed.The mechanism of the reaction is discussed and experimental conditions are described which gives highest yields of the desired products.

Full text of DOI:10.1039/DT9800001282

View Online / Journal Homepage / Table of Contents for this issue

View Online

View Online

View Online

View Online

View Online

View Online

View Online

View Online

View Online