Major
Chemistry
Research Abstract
Density functional methods have been used to study the mechanisms for the sequential electrocyclic ring closures of [16]annulene, with a goal of determining the likelihood of heavy-atom tunneling. Using M06-2X/6-31G*, we computed barriers of 27 and 13 kcal/mol for the first and second electrocyclizations, respectively, compared with 21 kcal/mol for the parent cyclization of 1,3,5-hexatriene. The second cyclization is predicted to have a lower and narrower barrier than the first cyclization, which suggests a higher probability of tunneling. However, if [16]annulene undergoes the first cyclization by passage over the 27 kcal/mol barrier, then it would have more than enough energy to pass over the second cyclization barrier as well, implying that tunneling would be insignificant.
Faculty Mentor/Advisor
William Karney
transcript
AngelaCastileKrasuski_6-ElectronElectrocyclizations_chemistry_poster.pptx (13959 kB)
PowerPoint
AngelaCastileKrasuski_6-ElectronElectrocyclizations_chemistry_audio.m4a (1416 kB)
mp4
Effect of Tunneling on 6-Electron Electrocyclizations
Density functional methods have been used to study the mechanisms for the sequential electrocyclic ring closures of [16]annulene, with a goal of determining the likelihood of heavy-atom tunneling. Using M06-2X/6-31G*, we computed barriers of 27 and 13 kcal/mol for the first and second electrocyclizations, respectively, compared with 21 kcal/mol for the parent cyclization of 1,3,5-hexatriene. The second cyclization is predicted to have a lower and narrower barrier than the first cyclization, which suggests a higher probability of tunneling. However, if [16]annulene undergoes the first cyclization by passage over the 27 kcal/mol barrier, then it would have more than enough energy to pass over the second cyclization barrier as well, implying that tunneling would be insignificant.
