hula-twist (HT) mechanism

https://doi.org/10.1351/goldbook.HT07393
Volume-conserving mechanism of @[email protected] of a double bond in a conjugated system involving simultaneous configurational and conformational @[email protected], e.g., the photoinitiated concerted rotation of two adjacent double and single bonds.
HT07393.png
Note:
Under unconstrained conditions, the conventional @[email protected] (OBF) process is the dominant process with the hula-twist (HT) being an undetectable higher energy process. It has been proposed that under confined conditions (e.g., a conjugated double bond @[email protected] in a protein cavity or in a solid matrix), the additional @[email protected] barriers make the OBF a less favourable process, allowing the volume-conserving HT to be the dominant process for @[email protected]
Source:
PAC, 2007, 79, 293. (Glossary of terms used in photochemistry, 3rd edition (IUPAC Recommendations 2006)) on page 352 [Terms] [Paper]