Kinetic Investigation of the Platinum‐catalysed Hydrosilylation of Vinylsiloxanes with Hydrogensiloxanes A kinetic investigation of the platinum‐catalysed hydrosilylation of monofunctional oligomeric vinylsiloxanes by monofunctional oligomeric hydrogensiloxanes was performed under stoichiometric conditions with use of quantitative 1H‐NMR spectrometry. The reaction rate up to 50% conversion can be expressed by v=k [Pt]. During further hydrosilylation the kinetic changed to second order. No induction period was observed. A hydrogensiloxane with a dimethylsilyl end group gives much higher rates than a siloxane with a methylsiloxy group. The main reactions of all hydrosilylations, determined by GC‐MS and 29Si‐NMR, are β‐additions. Less then 5% α‐products are obtained.

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Kinetic Investigation of the Platinum-Catalyzed Hydrosilylation of Vinylsiloxanes with Hydrogensiloxanes.-Hydrosilylation of vinylsiloxanes, e.g. (II) or (V), yields the β-addition product (III) besides less than 5% of the corresponding . alpha.-adduct. The reaction rate is, up to 50% conversion, linearly dependent on the catalyst concentration and later on of second order but is 15-fold higher with the terminal hydrogensiloxane (IV) in the second reaction despite lower temperature as compared with (I). -(BRAND, D.; MORETTO, H.-H.; SCHULZE, M.; WROBEL, D.; J. Prakt.

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