STEREOCHEMISTRY Flashcards
what are isomers
same type and number of atom
what are the two types of isomers
constitutional isomers
stereoisomers
what are the further types of steroisomers
Enantiomers
Cis/Trans isomers
Diastereomers (conformers/rotamers)
what are constitutional isomers
same molecular formula
different connectivity of atoms
what are stereoisomers
same molecular formula
different spatial orientation of atoms
how does geometric isomerism occur
occurs through cis and trans compounds
what does geometric isomerism occur in
In alkenes and cyclic compounds
how does a compound become a trans compound
substituents on opposite sides
how does a compound become a cis compound
substituents are on the same side of the ring or double bond
what composition of compound is more stable, trans or cis
trans
why is a trans isomer more stable than a cis isomer
substituents are further apart and there is less steric repulsion
what interaction would occur within cis-2-butene that makes it less stable
steric interaction [as substituents closer together]
what are chiral objects
not superimposable on their mirror images
what does achiral mean
superimposable on their mirror images
what does a chiral molecule contain
a carbon atom that is connected to four different groups.
This carbon that is connected to four different groups is called the chiral centre.
what makes two compounds stereoisomers
when the two compounds only differ from each other in spatial arrangement
what is an enantiomer
When a compound is chiral, it will have one non-superimposable mirror image. This is called an enantiomer.
what do enantiomers properties have in common
similar physical properties to each other
what are the steps to using the cahn-ingold-prelog system
1) assign the group in atomic number where highest atomic number given highest priority
2) make sure the lowest/fourth priority group is on the dash
3) count from 1-3 with an arrow to determine
when assigning priority number by highest atomic number - WHAT HAPPENS if the atom of the group the carbon is attached to is the same
if they are the same element i.e. carbon, then choose which group is more significant. so en ethyl group would take priority over a methyl group
how do you adjust so that the 4th group is on the lowest priority wedge
swap adjacent 4th priority group to the wedge
then swap other two numbers with each other
what happens if from 1-3 is anticlockwise
s-enantiomer
what happens if from 1-3 is clockwise
r-enantiomer
how is a double bond considered in cahn-ingold-prelog when assigning the priority number
2 separate bonds
how is a triple bond considered in cahn-ingold-prelog when assigning the priority number
3 separate bonds
according to cahn-ingold-prelog, how many bonds would carbon be bonded to from carbon dioxide on one oxygen
2 oxygen (due to double bond on the oxygen)
breakdown what (2R,3S)-3- methyl-2-pentanol means
there are two chiral centres
one at 2 - which is right configuration enantiomer
one at 3 - which is left configuration enantiomer
what are Diastereomers
stereoisomers that are not mirror images of one another.
what is an example of Diastereomers
Cis/trans isomers
