Illustrated Glossary of Organic Chemistry
Sigma
tropic reaction:
A
pericyclic reaction
in which one or more
sigma bonds
are converted to an equal number of new
sigma bonds
via a
cyclic
transition state
and an
intramolecular
process.
This [
1,5]-H shift
in a
1,3-diene
is a
sigma
tropic reaction.
This
Cope rearrangement
of a
1,5-diene
is a
sigma
tropic reaction, involving a
[3,3]-sigmatropic shift
.
This
Diels-Alder
[4+2]
cycloaddition reaction
is a
pericyclic reaction
, but it is not a
sigma
tropic reaction because it is not
intramolecular
, and because the number of
sigma bonds
lost from the
reactants
(one) is not the same as the number of
sigma bonds
gained in the
product
(two).
Related terms:
Woodward-Hoffmann rules
,
suprafacial
,
antarafacial
,
oxyCope rearrangement
,
Claisen rearrangement
,
concerted reaction
,
substitution reaction
,
elimination reaction
,
addition reaction
,
reduction reaction
,
oxidation reaction
,
arrows
,
Ph
,
reaction mechanism
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