10.1021/jo060698k.s001
Kimberly J. Daoust
Kimberly J.
Daoust
Susanna M. Hernandez
Susanna M.
Hernandez
Kaleen M. Konrad
Kaleen M.
Konrad
Iain D. Mackie
Iain D.
Mackie
James Winstanley
James
Winstanley
Richard P. Johnson
Richard P.
Johnson
Strain Estimates for Small-Ring Cyclic Allenes and Butatrienes
American Chemical Society
2006
cyclohexatriene
cyclic butatrienes
cyclic allene series
bicyclo
fragment deformation approach
kcal
cyclopentadiene
B 3LYP level
group strain estimates
cyclic allenes
2006-07-21 00:00:00
Journal contribution
https://acs.figshare.com/articles/journal_contribution/Strain_Estimates_for_Small_Ring_Cyclic_Allenes_and_Butatrienes/3069586
Isodesmic and homodesmic equations at the B3LYP/6-311+G(d,p)+ZPVE level of theory have been
used to estimate strain for the homologous series of cyclic allenes and cyclic butatrienes. A simple fragment
deformation approach also has been applied and appears to work better for the larger rings. For the
cyclic allene series, estimates for allene functional group strain (kcal/mol) include: 1,2-cyclobutadiene,
65; 1,2-cyclopentadiene, 51; 1,2-cyclohexadiene, 32; 1,2-cycloheptadiene, 14; 1,2-cyclooctadiene, 5; 1,2-cyclononadiene, 2; 1,2,4-cyclohexatriene, 34; and bicyclo[3.2.1]octa-2,3-diene, 39. For cyclic butatrienes,
functional group strain estimates include: 1,2,3-cyclobutatriene, >100; 1,2,3-cyclopentatriene, 80; 1,2,3-cyclohexatriene, 50; 1,2,3-cycloheptatriene, 26; 1,2,3-cyclooctatriene, 17; and 1,2,3-cyclononatriene, 4.
Barriers to interconversion of enantiomers in cyclic allenes are reduced with increasing strain. Newly
predicted values include: 1,2-cyclopentadiene <1 kcal/mol and bicyclo[3.2.1]octa-2,3-diene, 7.4 kcal/mol. Estimated levels of strain parallel the known reactivity of these substances.