Conformer-specific Chemistry Imaged in Real Space and Time

TL;DR

This study uses ultrafast electron diffraction to directly image how specific conformers of -phellandrene undergo a ring-opening reaction, revealing the influence of molecular conformation on reaction dynamics in real space and time.

Contribution

It provides the first direct, real-time imaging of conformer-specific reaction pathways in the gas phase, validated by quantum molecular dynamics simulations.

Findings

Conformers evolve into predicted isomers in real space and time.

Reaction dynamics are significantly influenced by molecular conformation.

Quantum efficiency varies with conformer during the ring-opening process.

Abstract

Conformational isomers or conformers of molecules play a decisive role in chemistry and biology. However, experimental methods to investigate chemical reaction dynamics are typically not conformer-sensitive. Here, we report on a gas-phase megaelectronvolt ultrafast electron diffraction investigation of {\alpha}-phellandrene undergoing an electrocyclic ring-opening reaction. We directly image the evolution of a specific set of {\alpha}-phellandrene conformers into the product isomer predicted by the Woodward-Hoffmann rules in real space and time. Our experimental results are in quantitative agreement with nonadiabatic quantum molecular dynamics simulations, which provide unprecedented detail of how conformation influences time scale and quantum efficiency of photoinduced ring-opening reactions. Due to the prevalence of large numbers of conformers in organic chemistry, our findings impact our general understanding of reaction dynamics in chemistry and biology.