How can "E/Z" isomers arise?

1 Answer
Feb 2, 2017

Consider the simple molecule "2-butylene..........."

Explanation:

Now for H_3C-CH=CH-CH_3 we can have 2 geometric isomers:

"cis-2-butylene" or "Z-butene"; or "trans-2-butylene" or "E-butene"

https://tse2.mm.bing.net/th?id=OIP.9O2vdqn26zm6igIH4e9o2AEsBc&pid=15.1&P=0&w=340&h=105https://tse2.mm.bing.net/th?id=OIP.9O2vdqn26zm6igIH4e9o2AEsBc&pid=15.1&P=0&w=340&h=105

For both isomers, the connectivity is MANIFESTLY the same: C1 connects to C2 connects......to C4. However, the geometry is manifestly different, and this geometric isomerism gives rise to different physical and chemical properties.

For example, "cis-2-butene" has a boiling point of 3.7 ""^@C; on the other hand, "trans-2-butene" has a boiling point of 0.9 ""^@C;