ISOMERISM Flashcards
what is a structural isomer
molecules with the same molecular formula but different structural formulas
3 types of structural isomerism
chain isomers
positional isomers
functional group isomers
what are chain isomers
occurs when there is more than one way of arranging carbon atoms in the longest chain
different arrangement of the hydrocarbon chain (branching)
chain isomer properties
similar chemical properties but slightly different physical properties
more branched , smaller surface area, weaker the VDW and so the lower the boiling point
what are VDWs
covalent bonds are strong IMFs
molecules also contain weaker IMFs which are forces between molecules
these IMFs are called van der waals forces
what are positional isomers
same carbon chain and functional group but the functional group is attached to the main chain at different points
what are functional group isomers
same molecular formula but different functional grups
what is stereoisomerism
molecules with the same structural formula but atoms arranged differently in space
two types
E-Z
optical isomers
reason behind stereoisomerism
double bond causes restricted rotation and so they cannot simply rotate, a bond must be broken
since this requires energy at room temp and pressure this energy isn’t available
this causes the restricted rotation and so enforces stereoisomerism
what is E-Z isomerism
two substituents may be on the same side (Z) or opposite sides of the bond (E)
each c=c must have at least one substituent group attached
CIP (Cahn Ingold Prelog) rules
assign priority of the two atoms attached to each side of the double bond
atom with the highest atomic number has highest priority
if they’re the same then look at the next atom in the group
what is cis
same side
what is trans
opposite sides
