Radicals derived from acetaldehyde and vinyl alcohol

Area of Science:

• Combustion Chemistry
• Theoretical Chemistry
• Spectroscopy

Background:

• Vinyl alcohol and acetaldehyde are isoelectronic products of incomplete butanol combustion.
• Radicals formed from these species are crucial intermediates in combustion processes.

Purpose of the Study:

• To computationally investigate the energetics and spectroscopic properties of vinyl alcohol and acetaldehyde related radicals.
• To refine existing theoretical models and provide new predictions for unobserved experimental data.

Main Methods:

• Utilized high-level ab initio methods, including coupled cluster theory with single, double, triple, and perturbative quadruple excitations (CCSDT(Q)).
• Employed large basis sets (cc-pV5Z) and incorporated corrections for relativistic effects, frozen core approximation, and Born-Oppenheimer approximation.
• Accounted for anharmonic zero-point vibrational energies.

Main Results:

• The syn conformer of vinyl alcohol is energetically favored over the anti conformer.
• The alcoholic hydrogen of syn-vinyl alcohol is the most easily removed.
• Predicted numerous fundamental vibrational modes for vinyl alcohol, acetyl, and vinoxy radicals, with several requiring reassignment of experimental data.

Conclusions:

• The study provides highly accurate energetic and spectroscopic predictions for key combustion intermediates.
• Findings can aid in refining butanol combustion models and further experimental spectroscopic characterization.
• Reassignments of specific vibrational modes in acetyl and vinoxy radicals are proposed based on theoretical results.