How do you name geometric isomers?
In chemistry we use L (levo), D (Dextro), and Iso (Isometric) to label our chemicals. We also use S,R, S', and R' respectively.
Notice there are a few symbols used here for LSD (Lysergic Acid Diethylamide):
"+", "-", and "iso"
In this case the iso refers to the placement of the Hydrogen at Carbon 8, and we use + and - instead of Levo and Dextro.
- (+)-LSD would be written Levo-Lysergic Acid Diethylamide;
- (-)-LSD would be written Dextro-Lysergic Acid Diethylamide;
- (+)-iso-LSD would be written Levo-iso-Lysergic Acid Diethylamide;
- (-)-iso-LSD would be written Dextro-iso-Lysergic Acid Diethylamide
Note that these are very informal but are very good to help you visualize the naming systems.
Also the 5R,8R :: 5R,8S :: 5S,8S :: 5S,8R refer to the labelled carbon groups 8 and 5 which are the only different isometric centers. Notice the bonding angles for them are different.