isomers & structural analysis

structural isomers

occur when atoms are bonded in a different order

chain isomer

when the hydrocarbon chain is arranged differently

• methyl group when before there wasn’t

positional isomers

when the functional group is placed differently on the chain

functional isomers

when there is a different functional group

stereoisomers

occur when atoms are bonded in the same order but are different in space

• cis-trans isomerism occurs when a double bond prevents the bond from rotating

optical isomerism

non-superimposable images (often occur when a central atom is attached to 4 other atoms)

cis-trans isomers

cis - each side of the double bond has hydrogen and another group

• cis - same side (H on the bottom & other on top)

• trans - opposite sides (diagonal to each other)

chiral

asymmetric in such a way that the structure and its mirror image are non-superimposable

• have 4 separate groups attached to the carbon

  • considered optically active

• only need 1 to be considered chiral

• carbons. ina ring - must be an asymmetrical ring to be chiral

• have no plane of symmetry

  • non-superimposable mirror images

  • many chiral molecules have a chiral carbon

  • DNA has chiral carbons & it is also chiral as there is no plane of symmetry

enantiomers

chiral atoms exist in different forms called enantiomers

they rotate plane polarized light in opposite directions and can be measured using a polarimeter - also called optically active

• rotate light diffferently

• similar chemical & physical properties

• can have different bio properties - they are stereospecific

superimposability

can perfectly overlap each other when in the same position

racemic mixtures (racemate)

have both enantiomers in equal concentration

when measured in a polarimeter, wil seem to be no effect on plane polarized light

• if one rotates it at 30 degrees in one direction, the other will rotate it 30 in the other direction, meaning no effect on the light as it cancels our