Organic structure 1-3 Flashcards
Isomers
molecules which possess the same molecular formula (C5H10O)
but are different
Constitutional isomers -
molecules which possess the same molecular formula but different
constitutions (connectivities).
Stereoisomers -
molecules which possess
the same molecular formula AND the same connectivity
Enantiomers -
stereoisomers which are mirror
images of each other
Diastereomers
- stereoisomers which are not
mirror images of each other.
Conformations
– different shapes possible
for a single molecule (usually related by
rotations about single bonds).
chiral centre –
four different groups on a carbon
if Stereoisomers are different molecules this means that…..
they have different properties from each other
what leads to the difference in qualities in isomers
they have Different interatomic distances this means different dipole moments, melting points,
boiling points, IR and NMR spectra,
solubilities, chromatographic properties etc.
draw Two enantiomers with achiral probe molecule
draw Two enantiomers with chiral probe molecule
chiral molecules can
can distinguish between enantiomers
How do you tell if a molecule is chiral?
-Take mirror image, see if it can be superimposed on original.
- consider symmetry of molecule.
does a achiral molecule plane of symmetry?
yes
High symmetry →
achiral
Low symmetry →
chiral
Molecule with a simple axis
of symmetry can be
chiral
Molecule with a plane or
centre of symmetry is
achiral
Molecule with a simple axis
of symmetry can be
chiral
Molecule with a plane or
centre of symmetry is
achiral
not all molecules without a plane or centre of symmetry
are chiral. Why?
This is because there are further symmetry elements* which can make a
molecule achiral
how to calculate the number of isomers?
2n stereoisomers? Where N is chiral centre number
Meso forms
are not optically active, does not have enantiomeric forms, but can have chiral shape
