Are cis- trans isomers and enantiomers both geometric isomers? and what is the difference between structural and geometric isomers? I know that there are structural isomers, cis-trans isomers, and enantiomers but i don't understand the concept.

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anonymous · Answer

This is a bit of a tricky one but here goes: cis-trans isomers are geometric isomers, as are enantiomers. Enantiomers are basically the same molecule but one is the mirror image of the other, so they are a subset of geometric isomers. cis-trans isomers are different in that the group which makes them different is on the other side of a double bond (usually a carbon-carbon double bond). Structural isomers are different molecules of the same chemical formula like 1,2 and 3 pentanol (there's a good section on Wikipedia about this. Please note the notation refers to the carbon atom on the chain which is bonded to the hydroxyl group). Another example might be a molecule with two groups on a benzene ring so there are a number of possible structural isomers.

To summarize, geometric isomers are different from structural isomers because the geometric isomers only differ by how the atoms are arranged in space. The geometric isomers can be split up further into enantiomers and cis-trans isomers as I mentioned above.