6.7 Specifications of Stereochemistry
187
6.7.1.1
Double Bond Systems
For vicinally disubstituted olefins (and similar double-bond systems) the
traditional prefixes cis and trans can be retained, although for all higher
substituted systems the descriptors (Z) and (E) as defined on the basis of
the CIP sequence rules must be applied.
cis- Pent -2-ene
(Z)-Pent -2-ene
~C02H
2-trans,4-cis-Hexa -2,4-dienoic acid
(2E, 4Z)-Hexa-2,4-dienoic acid
If in the above example the conformation relative to the 3,4-single bond
should also be specified, the supplemental prefixes s-cis (vs. s-trans) will
serve that purpose, thus giving: s-trans,(2E,4Z)-hexadienoic acid.
I
Br
l-cis,3-trans-Cycloocta-l,3-diene
(lZ,3E)-Cycloocta-l,3-diene
3-[trans- or (E)-2-(3-NitroN02 phenyl)ethenyl] pyridine
\..-./
(Z)-l ,2-Dibromo-l-chloro-2-iodoethene
Br;--\CI
~C02H
I
(E)-2-Methylbut-2-enoic acid
Piperonal (E)-oxime
trad.: Piperonal syn-oxime
M- OH
y-N 3.5.5-Tdmethylcyclohex-2-enone (Z)-oxime