Electrospray ionization
(ESI) is a process that entails flowing
liquids though metallic capillaries, typically held at voltages > 3
kV, leading to the formation of a fine spray of charged droplets (due to the
imbalance between the cohesive surface tension and repulsive electrostatics).
ESI is extensively used to characterize a diverse array of solutes, from simple
ions to complex macromolecular complexes, using mass spectrometry (MS) -
together, the platform is known as ESIMS. In the recent years, using ESIMS, researchers have reported that
a number of chemical reactions accelerate by orders of magnitude, when carried out
in ESI droplets in comparison to the reactions in the bulk phase. Examples
include, the phosphorylation of glucose and ribose, Pomeranz-Fritsch synthesis
of isoquinoline, the reaction between o-phthalaldehyde and alanine, and the
ozonation of oleic acid. However, the mechanisms underlying these dramatic rate
accelerations remain hotly debated. Most recently, using a variety of
experimental and computational tools, we have demonstrated that ESI of
solutions of water lead to gas-phase reactions, which are not representative of
the air-water interface at thermodynamic equilibrium. 1
Now, we would like to develop an reactor based on ESI to
investigate acid-catalyzed reactions towards the goal of producing high-value
chemicals, for instance, of interest to the pharmaceutical industry.Specifically, the Summer Intern will investigate operational
parameters, including the ionic strength and pH of water, ESI voltage, coaxial
gas-flow rate, length of the reactor, etc., to optimize conditions based on
reactions, such as the Fries Rearrangement of phenylacetate. We will analyze
the reaction products through nuclear magnetic resonance and chromatography
techniques.
References:
1.
Gallo, et al., Chemical Science (2019) DOI: 10.1039/C8SC05538F