CHIRALITY

stereoisomers

same molecular formula and connectivity

differ in orientation/3d

constitutional isomers

same molecular formula, differ in connectivity

type of stereoisomer without stereocenters

(achiral) cis trans isomers

type of stereoisomer with stereocenters

(chiral) enantiomers, diastereomers

types of isomers

stereo, consitutional

types of stereoisomers

achiral, chiral

enantiomer

nonsuperposable mirror images, chiral, show handedness

same physical properties

cause of enantiomers

carbon w 4 different groups (stereocenter)

nonsuperposable

when you flip the image/make a mirror image and it doesnt align/look the same

enantiomers always come in

pairs

a "pair" of \(R,R\) and \(S,S\) or \(R,S\) and \(S,R\)

what makes something achiral

objects that are superposable on mirror images (look the same even when flipped and it aligns)

rs config: what to do if least priority is in front

reverse the current answer

counting from 1 to 2 to 3 during rs configuration

ignore 4 if put in between

clockwise direction is R or S?

R

R or S counterclockwise

• S = Counterclockwise (left turn)

• R = Clockwise (right turn) [1, 2, 3]

stereocenter formula

2^n

diastereoisomers

superposable NON-mirror images, no pairs

different physical properties e.g. melting, boiling point

Ordinary light

Light waves oscillating in all planes perpendicular to its direction of propagation.

Plane polarized light

Light waves oscillating only in parallel planes.

Polarimeter

instrument for measuring ability of compound to rotate plane of plane polarized light.

Optically active

compound is capable rotating the plane of plane polarized light.

for chiral molecules (twists light waves)

dextrorotatory

enantiomer rotating light to right (clockwise)

levorotatory

enantiomer rotating light to left (counterclockwise)

compound with exactly 1 stereocenter is always

chiral and exists as a pair of enantionmers

no plane of symmetry possible

be careful when answering # of chirality centers or stereoisomers

stereoisomers uses formula 2^n. chirality centers just asks for # without using formula yet.

chirality of molecules in plant/animal living systems

chiral (except for inorganic salts, and a few low-molecular-weight organic substances)

how many stereoisomers is found in nature

1 specific

example of enzymes with many steroecenters

chymotrypsin (digestion of proteins in intestines of animals)

251 stereocenters so max possible 2251

only one of these stereocenters is produced and used

most produce/react if they match requirements

S ibuprofen vs. R

S is active, R is inactive

S naproxen vs. R

S is active

R is liver toxin

isomer diagram

how to find stereocenter

• there might be a hidden h counted as 1 different group

IGNORE

• double bond attached things

• secondary carbons without any substituent attached to it

• CH3 at end/primary carbons at the end

WATCH OUT

• watch out for identical groups bc that is equivalent to 1

finding stereocenter but it's a ring

1. follow path of carbon all the way back to starting point counterclockwise and clockwise

2. if paths in both directions same = NOT stereocenter (chiral center)

3. it's not the same if you encounter a substituent e.g. OH group sooner compared to the opposite path

enantiomers vs. diastereomers

enantiomers

• nonsuperposable

• mirror images

• come in pairs

• minimum chiral center: 1

• same physical properties (except optical stuff)

• no plane of symmetry

diastereomers

• nonsuperposable

• NOT mirror images

• has plane of symmetry

• minimum chiral center: 2

• different physical properties