# Studying the Intrinsic Reactivity of Chromanes by Gas-Phase Infrared Spectroscopy

## TL;DR

This study uses mass spectrometry and infrared spectroscopy to understand how chromane compounds break apart, revealing new insights into their chemical behavior.

## Contribution

The study introduces a combined experimental-theoretical approach to clarify fragmentation mechanisms of chromanes in different protonation states.

## Key findings

- Protonated Trolox and Methyltrolox fragment similarly via dehydration and decarbonylation.
- Deprotonated Methyltrolox shows unique radical fragmentation and a [1,2]-Wittig rearrangement.
- The approach reveals complex proton dynamics and intramolecular rearrangements in gas-phase chromanes.

## Abstract

Tandem
mass spectrometry is routinely used for the structural analysis
of organic molecules, but many fragmentation reactions are not well
understood. Because several potential structures can correspond to
a measured mass, the assignment of product ions is ambiguous using
mass spectrometry alone. Here, we combine mass spectrometry with high-resolution
gas-phase infrared spectroscopy and computational chemistry tools
to identify product ion structures and derive collision-induced fragmentation
mechanisms of the chromane derivatives Trolox and Methyltrolox. We
find that protonated Trolox and Methyltrolox fragment identically
via dehydration and decarbonylation, while deprotonated ions display
substantially diverging reactivities. For deprotonated Methyltrolox,
we observe unusual radical fragmentation reactions and suggest a [1,2]-Wittig
rearrangement involving aryl migration in the gas phase. Overall,
the combined experimental and theoretical approach presented here
revealed complex proton dynamics and intramolecular rearrangement
reactions, which expand our understanding on structure–reactivity
relationships of isolated molecules in different protonation states.