Which is a structural isomer of CH3CH2COOH that exhibits geometric isomerism?

1. CH3COOCH3
2. CH3CH(OH)CHO
3. CH3COCH2OH
4. HOCH=CHOCH3
5. CH3CH2COOCH3

im just confused oh how to approach the question :S
i drew them all out but still cannot figure it out
plz help :(

1 answer

I believe I'm right about this. In order to have a geometric isomer, a C=C bond must be present AND the atoms attached to the two C atoms must be arranged different spatially. As I see it, #4 is the only one possible. The H and H can be on the same side with the OH on the other side OR the H and OH can be on the same side with one of the H atoms on the other side. Restricted rotation is the key to geometric isomers and a double bond is the way to get restricted rotation. Two naming systems are the cis/trans or E/Z systems. Cis means on the same side/trans means on opposite sides. E means entgegen (opposite sides) and Z stands for zusammen (same side).