Photochemical Ring Openings are Complete in Picoseconds: A Time-Resolved UV Resonance Raman Study
A classic electrocyclic ring-opening reaction is the photoconversion of 1,3-cyclohexadiene (CHD) to cis-hexatriene (cis-HT). Our time-resolved resonance Raman studies have shown that the timescale for cis-HT formation is 8 ± 1 ps. To determine if the kinetics of CHD are representative of other photochemical ring-opening reactions, we have studied the photoconversions of 1,3,5-cyclooctatriene (COT) to octatetraene and of α-phellandrene (α-PHE) to 3,7-dimethyl-1,3,5-octatriene. COT is known to photochemically ring open with a disrotatory motion of the methylene portion of the ring as opposed to the conrotatory ring opening of CHD. α-PHE is a substituted 1,3-cyclohexadiene in which one of the carbons undergoing conrotatory rotation has a hydrogen substituted for an isopropyl group.
KeywordsRing Opening Difference Spectrum Formation Time Positive Peak Left Half