When shown diagrams of isomers, how can you determine which is a structural and which is a geometric isomer?

Question

Ellie Adams · Accepted Answer

The isomers of different connectivity are......

Geometric isomers are isomers that have a different geometry but the same connectivity as structural isomers. The word #"connectivity"# is key. Consider #"2-butylene"#, which structure can generate both cis and trans geometric isomers. For both geometries the connectivity is the same: #"C1 connects to C2, which connects to...C4"#. Nevertheless, the cis and trans isomers are manifestly different with respect to geometry, and are thus geometric isomers, or even diastereomers. (Note, here I use the definition that diastereomers are geometric isomers that are not mirror images.)

Santiago Alfonso · Answer

undefined Structural isomers have different arrangements of atoms in their molecular structure, while geometric isomers have the same molecular structure but differ in the spatial arrangement of atoms due to restricted rotation around a bond, such as in cis-trans isomers. In diagrams, structural isomers will show different connections between atoms, while geometric isomers will show different spatial orientations of groups around a double bond or ring.