Chirped-Pulse Fourier Transform Microwave Spectroscopy Coupled with a Flash Pyrolysis Microreactor: Structural...

Area of Science:

• Physical Chemistry
• Spectroscopy
• Molecular Structure Determination

Background:

• Cyclopentadienone (C5H4═O) is a crucial reactive intermediate in biomass decomposition and aromatic oxidation.
• Understanding its molecular structure is vital for controlling these processes.

Purpose of the Study:

• To investigate the molecular structure of cyclopentadienone using a novel spectroscopic technique.
• To precisely determine the positions of heavy atoms in cyclopentadienone.

Main Methods:

• Combination of chirped-pulse Fourier transform microwave spectroscopy (CP-FTMW) with flash pyrolysis (hyperthermal) microreactor.
• Generation of cyclopentadienone from o-phenylene sulfite pyrolysis.
• Observation of natural abundance (13)C isotopomers for precise structural analysis.

Main Results:

• The re molecular structure of cyclopentadienone was determined.
• Eight isotopomers, including (13)C substituted species, were analyzed.
• Comparison with computational data (CCSD(T) ab initio) validated the experimental findings.

Conclusions:

• The determined structure of cyclopentadienone reveals a pronounced C═C/C-C bond alternation.
• This structural feature disfavors the anti-aromatic zwitterionic resonance structure.
• The findings contribute to understanding the behavior of anti-aromatic molecules.