Neighboring Group Effects on the Rates of Cleavage of Si-O-Si-Containing Compounds

Ethan A. Gormong, Dorian S. Sneddon, Theresa M. Reineke, Thomas R. Hoye

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3 Scopus citations

Abstract

The presence of a nearby tethered functional group (G, G = tertiary amide or amine) can significantly impact the rate of cleavage of an Si-O bond. We report here an in situ 1H NMR spectroscopic investigation of the relative rates of cleavage of model substrates containing two different Si-O substructures, namely alkoxydisiloxanes [GRO-Si(Me2)-O-SiMe3] and carbodisiloxanes [GR-Si(Me2)-O-SiMe3]. The trends in the relative rates (which slowed with increasing chain length, with a notable exception) of alkoxydisiloxane hydrolyses were probed via computation. The results correlated well with the experimental data. In contrast to the hydrolysis of the alkoxydisiloxanes, the carbodisiloxanes were not fully hydrolyzed, but rather formed an equilibrium mixture of starting asymmetric disiloxane, two silanols, and a new symmetrical disiloxane. We also uncovered a facile siloxy-metathesis reaction of an incoming silanol with the carbodisiloxane substrate [e.g., Me2NR-Si(Me2)-O-SiMe3 + HOSiEt3 ⇋ Me2NR-Si(Me2)-O-SiEt3 + HOSiMe3] facilitated by the pendant dimethylamino group, a process that was also probed by computation.

Original languageEnglish (US)
Pages (from-to)1988-1995
Number of pages8
JournalJournal of Organic Chemistry
Volume88
Issue number4
DOIs
StatePublished - Feb 17 2023

Bibliographical note

Funding Information:
This research was supported by the National Science Foundation Center for Sustainable Polymers (CHE-1901635), an NSF-funded Center for Chemical Innovation (CCI). Support for NMR instrumentation came from a Shared Instrumentation Grant (NIH S10OD011952). Mass spectrometry data were collected using instrumentation from The University of Minnesota Department of Chemistry Mass Spectrometry Laboratory (MSL), supported in part by The National Science Foundation (NSF, Award CHE-1336940). DFT calculations were carried out using resources provided at the Minnesota Supercomputing Institute. D.S.S. appreciates the support from a Wayland E. Noland Fellowship.

Publisher Copyright:
© 2023 American Chemical Society.

PubMed: MeSH publication types

  • Journal Article

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