Exploring Field-Induced Fragmentation of Protonated Alcohols: Mechanistic Insights and Stabilizing Ion-Solvent...

Area of Science:

• Analytical Chemistry
• Physical Chemistry
• Computational Chemistry

Background:

• Field-induced ion activation in mass spectrometry (MS) and ion mobility spectrometry (IMS) can alter ion structures.
• Hydroxyl-containing compounds, particularly alcohols, undergo significant water loss (H2O), but mechanisms are poorly understood.
• Primary carbocations formed from primary alcohols are highly unstable, complicating fragmentation studies.

Purpose of the Study:

• Investigate the dynamics of field-induced fragmentation in protonated primary and secondary alcohols.
• Elucidate the fragmentation mechanisms and energetics.
• Explore stabilization effects of ion-solvent interactions.

Main Methods:

• Combined theoretical and experimental approach.
• Density functional theory (DFT) and reaction kinetics modeling.
• Fragmentation measurements using a HiKE-IMS-MS and tandem IMS device.

Main Results:

• Fragmentation mechanism involves a protonated cyclopropane (PCP+) moiety for both primary and secondary alcohols.
• Primary alcohols undergo an intramolecular S_N2 reaction facilitated by the PCP+ moiety, yielding a secondary carbocation.
• Protonated alcohols exhibit high fragmentation rates, indicating significant instability, but neutral water can form stabilizing ion-solvent clusters.

Conclusions:

• The PCP+ moiety is key to understanding alcohol fragmentation dynamics.
• Field-induced fragmentation is a significant factor affecting protonated alcohol stability.
• Ion-solvent clustering, particularly with water, offers a potential stabilization strategy for labile ions in MS/IMS.