title: A mechanistic study of the low pressure pyrolysis of linear siloxanes.
abstract: Matrix isolation IR spectroscopy has been used to study the vacuum pyrolysis of 1,1,3,3-tetramethyldisiloxane (L1), 1,1,3,3,5,5-hexamethyltrisiloxane (L2) and 3H,5H-octamethyltetrasiloxane (L3) at ca. 1000 K in a flow reactor at low pressures. The hydrocarbons CH3, CH4, C2H2, C2H4, and C2H6 were observed as prominent pyrolysis products in all three systems, and amongst the weaker features are bands arising from the methylsilanes Me2SiH2 (for L1 and L2) and Me3SiH (for L3). The fundamental of SiO was also observed very weakly. By use of quantum chemical calculations combined with earlier kinetic models, mechanisms have been proposed involving the intermediacy of silanones Me2Si=O and MeSiH=O. Model calculations on the decomposition pathways of H3SiOSiH3 and H3SiOSiH2OSiH3 show that silanone elimination is favoured over silylene extrusion.
authors.affiliation: School of Chemistry, University of Reading, Whiteknights, P.O. Box 224, Reading, UK RG6 6AD.
authors.forename: Matthew J
authors.initials: MJ
authors.lastname: Almond
authors.forename: Rosa
authors.initials: R
authors.lastname: Becerra
authors.forename: Sarah J
authors.initials: SJ
authors.lastname: Bowes
authors.forename: John P
authors.initials: JP
authors.lastname: Cannady
authors.forename: J Steven
authors.initials: JS
authors.lastname: Ogden
authors.forename: Nigel A
authors.initials: NA
authors.lastname: Young
authors.forename: Robin
authors.initials: R
authors.lastname: Walsh