Chirality & Stereochemistry

Non-superimposable mirror images

Objects or molecules that are mirror images of each other but cannot be perfectly overlapped, like the left and right hand.

chirality

A property where a molecule cannot be superimposed on its mirror image, similar to left and right hands.

enantiomers

are the two mirror-image forms of a chiral molecule.

Chiral center / Chiral carbon

A carbon atom attached to four different groups, making the molecule chiral (can form non-superimposable mirror images).

Diastereomers

Stereoisomers that are not mirror images of each other. They differ in configuration at one or more (but not all) chiral centers.

R/S configuration

A system used to assign the 3D spatial arrangement of groups around a chiral center as R (rectus) or S (sinister) based on priority rules.

Cahn–Ingold–Prelog (CIP) priority system

A set of rules used to assign priority to atoms/groups attached to a chiral center based on atomic number, used for determining R/S configuration.

Tautomerism

Tautomerism

when a molecule “switches forms” by moving a hydrogen and a double bond.

enantiomers

If you have two molecules that are mirror images and they cannot be perfectly superimposed, then they are:

chiral, and carbon must have 4 different groups

to be nonsuperimposable is to be what?

Bromochlorofluoromethane

cannot be superimposed

dichlorofluoromethane

can be superimposable

Stereoisomers

molecules that have the same components (atoms) connected in the same order but arranged differently in 3D space.

Stereocenter

it is a point of stereoisomerism.

Chiral center

a specific center attached to four unique groups

Achiral

SUPERIMPOSABLE mirror images

Chiral

Mirror images but non superimposable

Chiral center

It cannot have a pi bond (double or triple bond).

Stereocenter

• It can have a double bond but not a triple bond.

• It can be chiral or achiral.

racemic mixture

a 50-50 mixture of 2 enantiomers; A mixture containing equal amounts of two enantiomers (R and S forms). Because the optical activities cancel each other out, the mixture is optically inactive (does not rotate plane-polarized light).

2^n

how to calculate maximum # of stereoisomers?

achiral

symmetry

chiral

asymmetry

meso compound

has 2 or more chiral centers but because of symmetry, it became achiral

tetrahedral carbon

chiral carbon

levorotatory; light will go counter clockwise

what does L means in L/D naming?; direction

dextrorotatory; light will go clockwise

what does D means in L/D naming?; direction

Rectus=right=clockwise

what does R means in R/S naming?; direction

Sinister=left=counter clockwise

what does S means in R/S naming?; direction

Cahn-Ingold-Prelog-System

other name for R/S system

I, Br, Cl. S, P, O, N, C, H

palatandaan for atomic numbers increasing order