Abstract: The Diels-Alder reaction of phenylcthynylsilanes with tctraphenylcyclopcnta-dicnonc is used as the chief synthetic method for syntheses of polyphenylphenyl-organosilancs.Two different methods are available for synthesis of phenylethynyl methyl diethoxysilane.The physical constants of the two products,synthesized by two different methods,arc identical,confirming that the two products arc the same compound.