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ANIONIC REARRANGEMENTS FOLLOWING DECARBOXYLATION OF BENZOPHENONE DERIVATIVES
WITH CRYOGENIC IR SPECTROSCOPY
JOSEPH P. MESSINGER, EVAN H PEREZ, ANNA GABRIELLA DEL ROSARIO RULL ´
AN BUX ´
O,
TIM SCHLEIF, OLIVIA MOSS, Department of Chemistry, Yale University, New Haven, CT, USA; KIM
GREIS, Department of Molecular Physics, Fritz-Haber-Institut der Max-Planck-Gesellschaft, Berlin, Ger-
many; MARK JOHNSON, Department of Chemistry, Yale University, New Haven, CT, USA.
Carbanions are highly reactive intermediates that are commonly used in organic synthesis. Here, we investigate the
fundamental gas phase spectroscopy and isomerization of substituted aromatic phenides (deprotonated benzene derivatives)
using isomer-selective cryogenic ion vibrational predissociation spectroscopy (1000 cm
−1– 4200 cm
−1). The phenide is
formed by the decarboxylation of the 4-benzoyl benzoate anion (4BBA–, C14H9O3–), a substituted benzophenone, in a
commercial Orbitrap mass spectrometer before being transferred to the triple focusing time-of-flight photofragmentation
mass spectrometer. The resulting spectra are congested, suggesting the presence of multiple isomers. They are revealed
by quantum chemical calculations in conjunction with two color IR-IR photobleaching spectroscopy to be the expected
phenide, and a new molecule formed by multiple steps of isomerization that end in ring-closed product. The identities of
these compounds and the proposed mechanism are confirmed by additional experiments using 4BBA–-d9and 2BBA–.