Real-Time Monitoring of Reactions by Headspace Sampling under Ambient Mass Spectrometric Conditions

The helium-plasma (HePI) ionization mass spectrometrymethod wasused to track the formation of reaction products and consumption ofreactants by continually monitoring the vapors in the reaction headspacein real time. Two examples of the application procedure are presentedhere: a nucleophilic acyl substitution reaction and a 1,4-nucleophilicaddition process. For the purposes of the work, a specially constructedhelium-plasma ionization (HePI) source was mounted on a single-quadrupolebenchtop mass spectrometer. However, any electrospray source is easilyconvertible to an ambient HePI source. This setup has the potentialto be used in the teaching of organic and analytical chemistry laboratories,as well as for demonstrations. Because the procedure requires onlythe headspace of the reaction vessel to be sampled by an easily preparedVenturi suction device (pump), the experiments can be quickly setup and adapted for any available mass spectrometer equipped with anelectrospray source. For sampling, students can be shown how to preparetheir own Venturi pumps and conduct reactions at different temperatures.

Automated summary

The helium-plasma (HePI) ionization mass spectrometry method was utilized to monitor the formation of reaction products and consumption of reactants in real time. The application procedure included nucleophilic acyl substitution reaction and 1,4-nucleophilic addition process. The setup of HePI source on a mass spectrometer allows it to be used in organic and analytical chemistry laboratories for teaching and demonstrations. By sampling the headspace of the reaction vessel with a Venturi suction device, the experiments can be quickly set up and adapted for any electrospray equipped mass spectrometer.