chirality

constitutional/structural isomers e.g. C₂H₆O

compounds with the same molecular formula but different bond pattern

conformational isomers

compounds with the same molecular formula and bond pattern (stereoisomers) with rotations about single bonds only

configurational isomers

compounds with the same molecular formula and bond pattern (stereoisomers) that cannot rotate around single bonds only

chiral

molecules that cannot be superimposed upon their mirror images e.g. hand

has no plane of symmetry

optically active - can rotate the plane of polarised light

achiral

molecules that can be superimposed upon their images e.g. mirror images

any molecule with a plane of symmetry is achiral

enantiomers

a pair of molecules that are related as non-superimposable mirror images e.g. chiral molecules

each pair of enantiomers rotates the plane of polarized light in an opposite direction

enantiomers rotate light in opposite directions but by the same number of degrees

stereogenic center

a carbon with four different groups attached to it. Gives rise to two stereoisomers

chiral carbon

tetrahedral carbon attached to four different atoms or groups of atoms

its mirror image will become a different compound (enantiomer)

plane-polarized light

difference between two enantiomers

if one enantiomer rotates plane polarized by light by x degrees in a clockwise directions, then the other enantiomer will rotate plane polarized light by x degrees in the counterclockwise direction

d - dextrorotatory - (+) enantiomer → rotate clockwise

l - levorotatory - (-) enantiomer → rotate counterclockwise

racemic mixture

50-50 mixture of two enantiomers e.g. the (d, l) or (+, -) mixture will give no optical rotation as they will cancel each other out

specific rotation

observed rotation depends on the length of the cell and concentration, as well as the strength of optical activity, temperature, and wavelength of light

T is the temperature and λ is the wavelength of light