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

doi:10.1021/acs.joc.2c02126

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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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 language	English (US)
Pages (from-to)	1988-1995
Number of pages	8
Journal	Journal of Organic Chemistry
Volume	88
Issue number	4
DOIs	https://doi.org/10.1021/acs.joc.2c02126
State	Published - 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.

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© 2023 American Chemical Society.

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title = "Neighboring Group Effects on the Rates of Cleavage of Si-O-Si-Containing Compounds",

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.",

author = "Gormong, {Ethan A.} and Sneddon, {Dorian S.} and Reineke, {Theresa M.} and Hoye, {Thomas R.}",

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: {\textcopyright} 2023 American Chemical Society.",

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AU - Gormong, Ethan A.

AU - Sneddon, Dorian S.

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AU - Hoye, Thomas R.

N1 - 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.

PY - 2023/2/17

Y1 - 2023/2/17

N2 - 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.

AB - 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.

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U2 - 10.1021/acs.joc.2c02126

DO - 10.1021/acs.joc.2c02126

M3 - Article

C2 - 36745769

AN - SCOPUS:85147960772

SN - 0022-3263

VL - 88

SP - 1988

EP - 1995

JO - Journal of Organic Chemistry

JF - Journal of Organic Chemistry

IS - 4

ER -

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

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