Unraveling the Unimolecular Ion Chemistry of Protonated Isoprene and Prenol.
Edgar White BuengerPaul M MayerPublished in: Journal of the American Society for Mass Spectrometry (2023)
The atmospheric chemistries of isoprene and prenol have been studied extensively; however, much of that research has focused on neutral or radical chemistry. Recent studies have demonstrated that under acidic conditions, isoprene and prenol can become protonated in the atmosphere, and we have explored the unimolecular chemistry of protonated isoprene and prenol with tandem mass spectrometry (using a triple-quadrupole mass spectrometer) and density functional theory. The collision-induced dissociation of protonated isoprene revealed two product ion channels: the neutral losses of C 2 H 4 and H 2 , the former dominating over the latter. Protonated prenol dissociates by four product ion channels: the neutral losses of water, formaldehyde, methanol, and propene, with the former two being minor channels and the latter two being major channels. Density functional theory supplemented with CBS-QB3 single-point calculations revealed the underlying mechanisms to explain the breakdown behavior. The two competing channels from protonated isoprene could easily be rationalized due to the relative energy difference between key transition states along the reaction coordinates. However, in the case of protonated prenol, it was revealed that the minor products observed in the breakdown of protonated prenol had significantly lower reaction barriers when compared to the major products, an apparent contradiction. This could be rationalized if the initial ion population entering the collision cell is comproed of several isomeric species on the minimum energy reaction pathway, species populated by collisional excitation in the ion source region.
Keyphrases
- density functional theory
- tandem mass spectrometry
- molecular dynamics
- single cell
- liquid chromatography
- high performance liquid chromatography
- ultra high performance liquid chromatography
- simultaneous determination
- mass spectrometry
- high resolution
- gas chromatography
- stem cells
- computed tomography
- magnetic resonance imaging
- magnetic resonance
- drug discovery
- particulate matter
- cell therapy
- genetic diversity
- endothelial cells
- solid phase extraction
- air pollution
- diffusion weighted imaging
- molecular dynamics simulations