IUPAC > Gold Book > alphabetical index > E > E, Z
icon

IndexesDownload


E, Z

The approved stereodescriptors of stereoisomeric alkenes R1R2C=CR3R4 ( R1R2 , R3R4 ); neither R1 nor R2 need be different from R3 or R4 ), cumulenes R1R2C(=C=C)n=CR3R4 and related systems e.g. R1R2C=NOH , HON=C{[CH2]n}2C=NOH . The group of highest CIP priority attached to one of the terminal doubly bonded atoms of the alkene, oxime, etc. or cumulene (i.e. R1 or R2 ) is compared with the group of highest precedence attached to the other (i.e. R3 or R4 ). The stereoisomer is designated as Z (zusammen = together) if the groups lie on the same side of a reference plane passing through the double bond and perpendicular to the plane containing the bonds linking the groups to the double-bonded atoms; the other stereoisomer is designated as E (entgegen = opposite). The descriptors may be applied to structures with a fractional bond order between one and two; and to double bonds involving elements other than carbon. They are not used to describe ring substitution relationships.
Source:
PAC, 1996, 68, 2193 (Basic terminology of stereochemistry (IUPAC Recommendations 1996)) on page 2206
Interactive Link Maps
First LevelSecond LevelThird Level
GraphGraphGraph
Cite as:
IUPAC. Compendium of Chemical Terminology, 2nd ed. (the "Gold Book"). Compiled by A. D. McNaught and A. Wilkinson. Blackwell Scientific Publications, Oxford (1997). XML on-line corrected version: http://goldbook.iupac.org (2006-) created by M. Nic, J. Jirat, B. Kosata; updates compiled by A. Jenkins. ISBN 0-9678550-9-8. doi:10.1351/goldbook.
Last update: 2014-02-24; version: 2.3.3.
DOI of this term: doi:10.1351/goldbook.E01882.
Original PDF version: http://www.iupac.org/goldbook/E01882.pdf. The PDF version is out of date and is provided for reference purposes only. For some entries, the PDF version may be unavailable.
Current PDF version | Version for print | History of this term
picture