<p>Mass spectrometry-based
techniques have been widely used in reaction monitoring due to their high
sensitivity and ability to offer structure information by tandem mass
spectrometry. We applied nanoelectrospray mass spectrometry (nanoESI-MS) to
simultaneously monitor pre-catalysts, catalytic intermediates, reagents, and
products of palladium catalyzed Suzuki-Miyaura cross-coupling reactions. A set
of Pd cluster ions related to the monoligated Pd (0) active catalyst is
detected, and its deconvoluted isotopic distribution reveals contributions from
two neutral molecules. One is assigned to the generally accepted Pd (0) active
catalyst, seen in MS as the protonated molecule, while the other is suggested
to correspond to a deactivated form of Pd catalyst. Oxidative stress testing of
the synthetic model catalyst XPhos Pd cyclo-octadiene, performed using oxygen
and Fe(III), supported this assignment. Thus, the make-up of the monoligated
set of Pd (0) ions appears to indicate the oxidation state of the system. The formation
and removal of the oxidative addition intermediate during the catalytic cycle
was monitored to provide information on the progress of the transmetalation
step. </p>
<p> </p>
<p><a>Recently,
microdroplets created by ambient ionization source have been used as reaction
vessels to accelerate organic reactions. Field desorption mass spectrometry
under ambient conditions is applied to study solution-phase organic reactions
in micro-volumes. Compared to nanoelectrospray, it is noteworthy that radical
cations and formation of radical cation products are observed. Three reactions,
the hydrazone formation by phenyl hydrazine and indoline-2,3-dione, the
Katritzky reaction between a pyrylium salt and anisidine, and the Hantzsch
synthesis of 1,4-dihydropyridine, were investigated by this system and reaction
acceleration was observed to different extents. The increase in rate relative
to that for the corresponding bulk reactions is attributed to solvent
evaporation which increases concentration, and to the increase of
surface-to-volume ratio with enhanced interfacial reaction rate constants. Later work in this thesis describes explicit
solvent calculations to study the energies and structures of the hydrazone
formation reaction from phenylhydrazine and indoline-2,3-dione in acidic
methanol with density functional tight binding (DFTB) methods. Additionally,
the thesis covers MS based methods for determination of isoaspartate and
aspartate in peptide by gas-phase chemistry and detection of
S-nitrosoglutathione in exhaled breath condensate sample.</a></p>
| Identifer | oai:union.ndltd.org:purdue.edu/oai:figshare.com:article/17122004 |
| Date | 19 December 2021 |
| Creators | Xingshuo Chen (11790056) |
| Source Sets | Purdue University |
| Detected Language | English |
| Type | Text, Thesis |
| Rights | CC BY 4.0 |
| Relation | https://figshare.com/articles/thesis/MASS_SPECTROMETRY_FOR_REACTION_MONITORING_AND_REACTION_ACCELERATION/17122004 |
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