60 likes | 182 Views
A Few Things From the Organic Unit, Followed up. Geometric Isomers in Organic Molecules. The only type of geometric isomer “type” we will discuss is cis-trans isomerism With TM complexes, we had cis-trans isomerism in square planar and octahedral complexes
E N D
Geometric Isomers in Organic Molecules • The only type of geometric isomer “type” we will discuss is cis-trans isomerism • With TM complexes, we had cis-trans isomerism in square planar and octahedral complexes • Ligands were either 90° (cis) or 180° (trans) apart from one another • Cis = “same side”; trans = “across from one another” • In organic molecules, cis-trans isomers can occur in certain alkenes • Alkene a double bond is necessary (but not sufficient
Example of a cis-trans isomer pair Trans = “opposite sides of double bond” (across the double bond) Cis = “same side of double bond”
These two compounds are only different because rotation about a db is restricted—a p bond would need to break
When is cis-trans isomerism possible? D A C C B E • Consider the following “generalized” alkene with substituents • To have cis-trans isomers, bothof the following must be true: • A B AND • D E