Topic 17.1 Chirality

One that cannot be superimposed on its mirror image (has 4 different groups attached)

The opposite of chiral

–> The mirror image of chiral molecule Optical isomers or enantiomers are chiral molecules (when they can’t be superimposed)

Lactic acid is chiral. The two forms have identical chemical reactions and physical properties except for the effect on plane-polarised light. –> Optical isomers polarise light in opposite directions (rotate 90° oppositely)

A mixture containing equal quantities (1:1) of the enantiomers is called a racemic mixture or racemate. -They have no overall rotation (as they are rotated to same so there is no change) -Optically inactive —> Made in nucleophilic addition

S- substitution N- nucleophile 2- bimolecular (2 molecules involved is RDS) Results in optically active product due to inversion. (The dashed lines in the transition state show partial bonds- those being woken and formed)

S- substitution N- nucleophile 1- 1 molecule involved in RDS Products, in theory, will be a racemic mixture due to planar intermediate.

Chiral molecule interacts with linear plane of polarised light -Molecule will rotate the plane Dextroration- clockwise Levorotation- anticlockwise

use of a polarimeter to measure optical activity light passes through a polariser which converts unpolarised to polarised. then through sample tube containing substance. if optically activated plane will be rotated. analyser is rotated