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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.
4
votes
Accepted
Difficulty in E-Z nomenclature and counting number of geometrical isomers
Rishi Shekher: You are correct that there are only four stereoisomers (A, B, C, D) of this tetraethylidenecyclobutane. Loong has given you a lead as to how to apply CIP rules to the assignment of the …
5
votes
Accepted
How many geometrical isomers will be formed here?
A possible reason you are being led astray is related to the way the substituents on the right side of the tri-substituted double bond are drawn in a linear fashion. However, when the hydrogen and the …
5
votes
Chiral centres with stereoisomeric substituents
Let's address your concerns one at a time:
The structure 1 you have drawn is chiral with $\ce{C4}$ having four different groups attached to it. $\ce{C4}$ has the (S)-configuration with the CIP priori …
7
votes
Number of Stereoisomers of C(CHClCH3)4
To answer your question, if you haven't figured it out by now, RRSS is the same as RSRS and it is the only one of the five that is optically inactive (Compare with nonactin). Structure A numbers the p …
13
votes
Accepted
Can geometrical isomers be enantiomers?
The enantiomers 1a and 1b can have their double bonds defined by CIP rules 1a and 5. Rule 1a dictates that CH3>H while Rule 5 has R>S. Thus, 1a has an E-double bond and 1b is of the Z-configuration a …
13
votes
How to check for geometrical isomerism in cyclic compounds?
I hope the statutes of limitation haven't run out. Structure 1 is a (Z)-alkene. Using Cahn-Ingold-Prelog (CIP) protocol, the rings are deconstructed as shown in diagram 2. The larger red arrow marks t …
1
vote
E - Z configuration of cyclic substituents
Welcome to Chem SE, A Singh: You have done a nice job laying out the digraphs for the cyclopropene (A) and cyclohexene (B) rings. The double bond in A is accessed early in both directions but only in …
13
votes
Number of stereoisomers of tetramethylspirononane
Here is another approach to @loong's solution to the seven stereoisomers of this tetramethyl spiro[4.4.0]nonane. [This question is akin to one recently asked about tetramethylspiropentanes].
Using t …
3
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How many cis-trans isomers does 1-O-stearoyl-2-O-arachidonyl-phosphatidyl-inositol-4',5'-bis...
Perhaps the answer is correct. If by cis/trans isomers the question includes the four stereogenic double bonds of the arachadonic acid chain and the six stereogenic carbons of the inositol ring, then …