Isomers or whatever

Isomerism

Same molecular formula, but different

Constitutional Isomers

Same formula, different connectivity

Stereoisomers

Same formula, same connectivity. Two different types

Configurational Isomers

Type of stereoisomer (same formula, same connectivity). Does not differ by rotation around a single bond only. Two types.

Conformers

Type of stereoisomer (same formula, same connectivity), Only different by rotation around a single bond.

Diastereomers

Type of Conformer (type of stereoisomer, same formula, same connectivity, and only different by rotation around a single bond)
Not mirror image
Example: cis- and trans- isomers

Enantiomer

Type of Conformer, (type of stereoisomer, same formula, same connectivity, and only different by rotation around a single bond)
Is a mirror image

Z configuration

In a double c=c bond, the higher priority groups are on the same side

E configuration

In a double c=c bond, the higher priority groups are on the opposite side

If a molecule and its mirror image rapidly interconvert

Effectively achiral

Interconversion by Chair Flip

A chair is flipped so that the most outward bottom carbon is converted to the topmost outer carbon and the chair is mirrored.
Axial and equitorial bonds convert into the other.
Only need rotation to become superimposable

Staggered Conformation

Type of conformer. When the back carbon is bisected by the front carbon

Gauche Conformation

Type of staggered conformation where the bulky groups are 60° apart rotationally (left or right)

Eclipsed Conformation

Type of conformer. When the back carbon is covered by the front carbon

Anti conformation

Type of staggered conformation where the bulky groups are 180° apart rotationally

Equatorial bonds

On the plane

Axial bonds

Perpendicular to the plane

(IHD) Index of Hydrogen Deficiency

half the number of H atoms missing from the molecular formula of an analogous (same number and type of each non-hydrogen atom) saturated molecule.

IHD Formula

(2(# of C atoms) + 2 + (# of N atoms) − (# of halogen atoms))/2

Counting IHD

Each double bond contributes 1 to a molecule’s IHD.

Each triple bond contributes 2 to a molecule’s IHD.

Each ring contributes 1 to a molecule’s IHD