Stereochemistry

isomer

same molecular formula but different connectivity

constitutional isomer

same molecular formula different bond connectivity(structure different)

stereoisomer

same bond connectivity and molecular formula but different 3D arrangement(cis/trans or enantiomers)

enantiomers

mirror images and non-superimposable(opposite to each other)

diastereomers

not mirror image and non-superimposable

chirality with Stereoisomers

opposite of all chiral is enantiomers(R to S) but at least one chiral is same and others are different is diastereomers

meso compound

identical, mirror image, plane of symmetry, has 2 or more chiral

chiral vs achiral

not identical but mirror is chiral and identical and mirror is achiral

How to determine Z and E

cover half and rank the molecules if both are on the same side its Z if opposite it is E

when is it not cis/trans and not Stereoisomerization and not /Z

when the end of the double bond has 2 Hs

recognize meso compounds

1. same substituent per chiral center

2. opposite chirality(R/S or S/R)

how to lock in geometry for cis/trans

pi bonds or rings

trans in rings

wedge=up and dashes= down

gauge

staggered conformation where 2 methyl groups are next to each other, higher in energy due to steric hindrance(60)

anti

2 methyl groups are positioned opposite of each other (180)

what is this

eclipsed

what is this

staggered

racemixture

equal amounts of enantiomers. Such mixture do not rotate plane-polarized light