Abstract: Despite the seeming similarity of the infrared (IR) spectra between tert-butyl cations (t-Bu) in gaseous and condensed phases, there are important but so far unrecognized differences. The IR spectroscopic investigation of the hydrogen (H)-bonding of t-Bu+ with the immediate environment together with the X-ray crystallographic data shows that one CH, group of t-Bu+ differs from the other two. In the Ar-tagged t-Bu in vacuum, this group is predominantly polarized, showing three C-H stretch vibrations at 2913, 2965, and 3036 cm(-1) whereas the other two methyls are predominantly involved in strong h-yperconjugation, yielding an intense triple IR band with a maximum at 2839 cm(-1). In a condensed phase, the bulk solvent effect promoted participation of the polarized CH3 group in additional hyperconjugation, decreasing its vCH(3) frequencies by approximately 120 cm(-1), whereas frequencies of the other CH, groups decreased by only ca. 4-10 cm(-1). This observation indicates that the influence of the condensed phase on t-Bu+ stabilization is substantial. Thus, enhancement of H-bonding between t-Bu and Anion-strengthens h-yperconjugation and promotes further cation stabilization.

Cite: Stoyanov E.S. , Gomes G.d.P.
tert-Butyl Carbocation in Condensed Phases: Stabilization via Hyperconjugation, Polarization, and Hydrogen Bonding
Journal of Physical Chemistry A. 2015. V.119. N32. P.8619-8629. DOI: 10.1021/acs.jpca.5b04657 WOS Scopus

Dates:

Published online:	Jul 29, 2015
Published print:	Aug 13, 2015

Identifiers:

Web of science	WOS:000359683400007
Scopus	2-s2.0-84939125134
OpenAlex	W2399808028

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