Organotrifluoroborates serve as coupling partners during transmetalation in the Suzuki–Miyaura reaction but require hydrolysis prior to the coupling reaction. Their anionic nature allows study of their hydrolysis by electrospray ionization mass spectrometry (ESI‐MS) through real‐time monitoring, complemented by pH analysis. The induction period varied according to the borates employed, and a dynamic series of equilibria for numerous ions was observed during hydrolysis. We found that the induction periods and reaction rates were sensitive to the R group of the borates, the shape of the reaction vessel, and stir rate.
<p>The
abundance of an ion in an electrospray ionization mass spectrum is dependent on
many factors beyond just solution concentration. Even in cases where the ions
are permanently charged and do not rely on protonation or other chemical
processes to acquire the necessary charge, factors such as cation structure,
molecular weight, solvent, and the identity of the anion can perturb results. Screening
of a variety of combinations of cation, anion and solvent provided insight into
some of the more important factors. Rigid cations and high conductivity anions
tended to provide the highest responses, while acetonitrile was the most
accurate solvent for reflecting solution composition. Functional groups that
had affinity for the solvent tended to depress response. These observations
will provide predictive power when accounting for ions that for reasons of high
reactivity can not be isolated.</p><br>
<p>The
abundance of an ion in an electrospray ionization mass spectrum is dependent on
many factors beyond just solution concentration. Even in cases where the ions
are permanently charged and do not rely on protonation or other chemical
processes to acquire the necessary charge, factors such as cation structure,
molecular weight, solvent, and the identity of the anion can perturb results. Screening
of a variety of combinations of cation, anion and solvent provided insight into
some of the more important factors. Rigid cations and high conductivity anions
tended to provide the highest responses, while acetonitrile was the most
accurate solvent for reflecting solution composition. Functional groups that
had affinity for the solvent tended to depress response. These observations
will provide predictive power when accounting for ions that for reasons of high
reactivity can not be isolated.</p><br>
Magnesium
impacts key processes in brewing including yeast metabolism and mash pH but is
typically overshadowed in brewing studies, owing to the established centrality
of calcium. Using flame atomic absorption spectroscopy (FAAS), we have
identified a 33.7% average increase in magnesium concentration in commercially
available beers brewed with 100% barley malt versus those brewed with adjunct
grains. Parallel analysis of brewing grains implicates rice in driving this
discrepancy. Given the known catalytic properties of magnesium, we investigated
its role in beer color development via Maillard chemistry using model systems
and wort (unfermented beer). Kinetic data were obtained by ultraviolet-visible
spectrometry and reaction species were identified by electrospray ionization
mass spectrometry. Magnesium accelerated Maillard chemistry in all systems in a
dose-dependent manner. It is proposed that magnesium inhibits water mobility
and serves as a Lewis acid catalyst to facilitate Maillard reactions.
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