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Questions tagged [cis-trans-isomerism]

Stereoisomeric olefins, cycloalkanes, etc. which differ in the positions of groups relative to a reference plane: in the cis-isomer the atoms are on the same side, in the trans-isomer they are on opposite sides. An obsolete synonym, for which the usage is strongly discouraged, is geometric isomerism.

According to the IUPAC Gold Book:

geometric isomerism [obsolete]
(DOI: 10.1351/goldbook.G02620)
Obsolete synonym for cis-trans isomerism. (Usage strongly discouraged).

cis-trans isomers
(DOI: 10.1351/goldbook.C01093)
Stereoisomeric olefins or cycloalkanes (or hetero-analogues) which differ in the positions of atoms (or groups) relative to a reference plane: in the cis-isomer the atoms are on the same side, in the trans-isomer they are on opposite sides.

Examples of cis-trans isomers

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Why are oxime geometrical isomers stable?

231st page of Clayden OC 2nd edition: Unlike the geometrical isomers of alkenes, however, those of an imine usually interconvert quite rapidly at room temperature. The geometrical isomers of oximes on the other hand are stable and can even…
EJC
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Confusion on syn and anti

I came across the following compound syn acetaldoxime However why is it syn because the lone pair having lowest priority is anti to H which is lowest priority on other side. Please clarify
user43496
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Does 1,3‐dichloroallene show geometrical isomerism?

Since the attached groups are present in different planes, $\ce{ClCH=C=CHCl}$ should not show geometrical isomerism, but my book say that it does. Why?
Abhishek Kumar
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Cis/Trans Isomerism in Cycloalkenes

How do I tell which one is cis/trans? I know the definitions: cis is same side; trans is across; but 1) What am I comparing here. 2) How do I compare/visualize?
Dissenter
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Why is tautomers not possible in benzoquinone?

1,4-Benzoquinone, commonly known as para-quinone, is a chemical compound with the formula $\ce{C6H4O2}$ When there are alpha Hydrogen's why can't it show tautomerism?
user27533
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E and Z configuration

In the above we need to find the configuration of the two double bonds whether (E) or (Z) according to me the one with the cyanides should be (E) and the other (E) however my book say that the correct answers are (E,Z) (in the same order as above)…
user43496
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Geometrical isomerism in spiro structures

The following structure shows Geometrical isomerism (GI for short) because the -Cl and -Br are in same plane This structure does not show GI because the -Cl and -Br are in perpendicular planes and the distances between the atoms remain same But I…
Ninjametry
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E - Z configuration of cyclic substituents

The answer is coming out as Z but given is E. I’m not sure where I’m wrong at this point as I moved along one chain at a time and wanted to follow heaviest atom as earliest as possible !
A Singh
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Conversion of cis to trans isomer

why in cis and trans isomers the double bond cannot be broken once and again joined to convert them from cis to trans is this type of bond breaking not allowed or is this allowed?
Kiran Thapliyal
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Please explain plane of symmetry

i am getting option (a) but answer is (b) where i am going wrong please help SO IT IS OPTION A ONLY FOR ME BUT HOW B HAS PLANE OF SYMMETRY PLEASE HELP
Jhagrut Lalwani
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