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What is the difference between isomers?

I know what a structural isomer is, but I'm a little bit confused about, what a stereo-isomer? What a geometric isomer? What an optical isomer is? And the difference between a stereo-isomer and a geometric isomer?

(edited 9 years ago)

Reply 1

anosmianAcrimony

Stereoisomers are molecules that share a structural formula but have a different arrangement in space. Geometric isomerism is a subset of stereoisomerism - all geometric isomers are stereoisomers, but there are other types of stereoisomerism besides geometric isomerism. I hope that makes sense.

Specifically, geometric isomerism refers to stereoisomerism produced by non-rotation of groups around (usually) a double bond. For example, the two molecules below are geometric isomers. Geometric isomerism is also called cis/trans isomerism. Molecule I is the cis isomer, and molecule II is the trans isomer.