%0 Journal Article
%A Doering, W. von E.
%A Benkhoff, Johannes
%A Carleton, Peter Smart
%A Pagnotta, Marco
%D 1997
%T Conjugative Interaction in Styrenes
%U https://acs.figshare.com/articles/journal_contribution/Conjugative_Interaction_in_Styrenes/3665511
%R 10.1021/ja971040e.s001
%2 https://acs.figshare.com/ndownloader/files/5755242
%K ΔΔ
%K ConjInter
%K kcal
%K styrene
%K Styrenes Conjugative interactions
%K phenyl
%K conjugative interaction
%X Conjugative interactions of the carbon−carbon double bond are
fundamental in organic chemistry. In
this work, equilibria are established among conjugated and unconjugated
isomers of two β-substituted styrenes,
1-phenylbut-1-ene and 1-phenyl-3-methylbut-1-ene, and one
α,β-disubstituted styrene, 2-phenyl-5-methylhex-2-ene,
over a range of temperatures (the van't Hoff method) in
hexamethylphosphoric triamide and potassium
tert-butoxide.
From the trans styrenes of the first two sets, an enthalpy of
conjugative interaction of phenyl
vis-à-vis alkyl
(ΔΔHConjInter/Alk) = −2.5 ± 0.2
kcal/mol [−5.1 kcal/mol defined as phenyl
vis-à-vis hydrogen
(ΔΔHConjInter/H)] is
observed, while the cis styrenes reveal an attenuated
ΔΔHConjInter/Alk of −1.1 kcal/mol
(ΔΔHConjInter/H = −2.7
kcal/mol). The α-methyl group in the third set also leads to a reduced
conjugative interaction. Entropy plays an important
role in determining positions of equilibrium. Free energies of
conjugation are reported for several sterically hindered
o-methyl-substituted styrenes.
%I ACS Publications