Geometric vs Structural Isomer

[chrisf]

Can someone differentiate between a geometric and structural isomer quickly?

Would a geometric isomer be, basically, the same molecule but arranging it so that an atom has a different hybridization/spatial arrangement? Basically, you could end up with a cis- and trans- configuration because of restricted rotation.

I understand that a structural isomer is a molecule with the same molecular formula, but differ structurally in the sequence in which the atoms are linked (propyl alcohol and isopropyl alcohol). Bonds have to physically break and rearrange. This means a different melting point and boiling point.

[chemnut]

Sounds to me like you have the idea. Here's a quote from chemguide.co.uk (one of my fave chem sites) about geometric isomerism:

"In stereoisomerism, the atoms making up the isomers are joined up in the same order, but still manage to have a different spatial arrangement. Geometric isomerism is one form of stereoisomerism."

He then goes on to talk about cis-trans isomerism as geometric isomerism.

Here's the isomerism menu page:

http://www.chemguide.co.uk/basicorg/isomermenu.html#top

You can read about structural isomers there, too if you want.

[chrisf]

Sweet. Thanks. Test on Wednesday, and he made it very clear today he's going to be very, very tricky.. so I'm making absolutely sure I know/understand every aspect of the things we've talked about.

Thanks again!

[chemnut]

You're welcome. I didn't really understand cis-trans until I read the explanation on chemguide. Something about the way he explained it just clicked finally.

Good luck on your test Wednesday. Our first test is Thursday!