Why do geometric isomers exist in some alkenes?

1 Answer
anor277
May 19, 2018

Because there is no possibility of free rotation around an olefinic bond...

Explanation:

Consider #"2-butylene"#...there are TWO GEOMETRIC ISOMERS POSSIBLE....

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For BOTH isomers, the #C-C# connectivity is PRECISELY the same...i.e. we got #H_3stackrel(1)C-stackrel(2)CH=stackrel(3)CH-stackrel(4)CH_3#...but CLEARLY, the geometry of each species is different...and this results in DIFFERENT chemical and physical properties....for instance normal boiling points of #3.7# #""^@C# (cis), and #0.90# #""^@C# (trans)...

Such isomerism is also possible for disubstituted rings..and given #"1-3, dimethylcyclohexane"#, how would you represent this?

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