Isomerism

Isomerism

1. Structural isomerism

   • chain isomerism
     • same functional gp
     • structural isomers that differ in the length of the main carbon chain
   • Position isomerism
     • differ only in the position of the functional group
     • same functional gp
   • Functional Group isomerism
     • belongs to different homologous series

2. Stereoisomerism

   • cis-trans isomerism
     • when there is C=C double bond, rotation is restricted
     • CIS-
       • same side
       • has net dipole moment
         • a slightly more polar molecule
         • higher boiling point
     • TRANS-
       • Opposite side
       • no net dipole moment
         • non-polar
         • lower boiling point
   • Enatiomerism
     • image is not superimposable
     • a carbon atom bonded to 4 different atoms / functional groups
     • middle carbon: chiral* carbon
     • similar physical properties
     • different interaction with polarized light
       • plane of polarized light is rotated
       • can be measured using a polarimeter
       • |+x|=|-x|: same extent of rotation

3. def: same molecular formula but different arrangements of atoms in space