Spatial isomerism is one that can only be explained by means of spatial structural formulas. It will only be possible to differentiate isomers through spatial molecular models.
It is divided into two types:
- cis-trans geometric isomerism
- optical isomerism
Cis-trans geometric isomer
Cis-trans geometric isomerism occurs when a pair of isomers have the same molecular formula but are different in their structural formulas. It can occur in two cases:
- in double bonded compounds
- in cyclic compounds
Double bonded compounds
The isomers should have carbons joined by a double bond and different binders attached to each carbon of the double bond.
Let be the double bond between C = C and its ligands a B C D, the condition for cis-trans geometric isomerism to occur must have its ligands The and B different and ç and d many different.
The molecular formula C2H2Cl2 can represent two molecules with different structural formulas.
Note that the linking atoms H and Cl are on the same side in the formula on the left. They are in opposite positions in the formula on the right. For this reason, we give different names for these isomers.
Indicates equal atoms on the same side with respect to the carbons of the double. The word cis comes from Latin and means "short of".
Indicates that atoms are in transverse or opposite positions relative to the carbons of the double. The word trans comes from Latin and means "beyond."
Correct nomenclature of these isomers:
For this isomerism to occur in cyclic compounds, it is necessary that at least two carbons of the cycle have different binders.
In this molecule, the carbon ligands are different:
This special case of isometrics can also be called isomerism. Baeyerianin honor of the scientist Adolf von Baeyer.