Separation of the isomers of oligomethylphenylcyclosiloxanes and determination of their structures by capillary GC-MS

Cyclic (MePhSiO)(n), formed by hydrolysis of MePhSiCl2, was analyzed by GC-MS on an HP-5 ms capillary column and separated into two different isomers of 2,4,6-trimethyl-2,4,6-triphenylcyclotrisiloxane (P3), four different isomers of 2,4,6,8-tetramethyl-2,4,6,8-tetraphenylcyclotetrasiloxane (P4), and four different isomers of 2,4,6,8,10-pentamethyl-2,4,6,8,10-pentaphenylcyclopentasiloxane (P5). Statistical distribution of the isomers was observed for every oligomethylphenylcyclosiloxane (P3, P4, and P5) with some steric effects of the phenyl group. Dissociation of the molecular ions was deduced from the mass spectra.