29304-70-9Relevant academic research and scientific papers
CROSS-CONJUGATED POLYENES / Part III. The molecular structures of gaseous bis(4,4-dimethyl-2,5-cyclohexadiene-1-ylidene) and 4,4-dimethyl-1-methylene-2,5-cyclohexadiene
Traetteberg, M.,Bakken, P.,Almenningen, A.,Luettke, W.,Janssen, J.
, p. 87 - 104 (1982)
The molecular structures of bis(4,4-dimethyl-2,5-cyclohexadiene-1-ylidene) (1) and 4,4-dimethyl-1-methylene-2,5-cyclohexadiene (2) have been studied by the gas electrondiffraction method.Both molecules were found to have non-planar carbocyclic rings that may be described by C6-C1-C2=C3 dihedral angles of 9.7 and 7.9 deg respectively for the former and latter compounds.The CC double bond at the bridge in the pentaene molecule (1) was found to be significantly longer than those in the ring .
The cyclohexadienyl radical in the thermal syn-anti isomerization of two crossed pentaenes of the type of bis-homofulvalene
Doering, W. Von E.,Birladeanu, Ludmila,Sarma, Keshab,Shao, Li-Sming
, p. 6660 - 6665 (1996)
To augment the elucidation of the dependence of enthalpy of stabilization on configuration among the pentadienyl radicals, a designer pentaene of the (Z,Z) type, (R,R)-5,5',6,6',7,7',8,8'-octahydro-4a,4a'-dimethyl-2,2'-bi-4a(H)-naph thylidene, has been prepared and subjected to a kinetic study of cis, trans isomerization about its central double bond. The resulting activation parameters and those of a more complicated example, 3,3'-bicholesta-1,4-dienylidene, are essentially identical, their mean values being ΔH(≠) = 36.8 kcal/mol and ΔS(≠) = +1.8 eu. This enthalpy of activation is significantly higher than those of pentaenes of the (E,E) and (E,Z) configuration. Conjugative interaction in coplanar cross-conjugated systems of the bis-homofulvalene type not having been experimentally evaluated or estimated by theoretical calculation, an enthalpy of stabilization for the cyclohexadienyl radical is not definitively to be extracted at the present time. If conjugative interactions are to be equated to four Kistiakowsky butadiene units and the difference in steric energies between educt and 90°-twisted state are to be estimated by the MMEVBH program, an enthalpy of stabilization of the cyclohexadienyl radical of ~20 kcal/mol results.
