Stereoisom Stereoisom er er Descriptor Descriptor
Jan 15, 2016
StereoisomerStereoisomer
DescriptorDescriptor
StereoisomerStereoisomer
EnantiomerEnantiomer DiastereomerDiastereomer Erythro, threo Erythro, threo Meso CompoundMeso Compound EpimerEpimer ChiralChiral Molecules With No Chiral Molecules With No Chiral
CentersCenters
DefinitionsDefinitions StereoisomersStereoisomers – compounds with the – compounds with the
same connectivity, different arrangement same connectivity, different arrangement in in spacespace
EnantiomersEnantiomers – stereoisomers that are – stereoisomers that are non-superimposible mirror images; only non-superimposible mirror images; only properties that differ are direction (+ or -) properties that differ are direction (+ or -) of optical rotationof optical rotation
DiastereomersDiastereomers – stereoisomers that are – stereoisomers that are not mirror images; different compounds not mirror images; different compounds with different physical propertieswith different physical properties
enantiomerenantiomer
Erythro dan threoErythro dan threo
Diastereomer:Diastereomer:Stereoisomer yang bukan Stereoisomer yang bukan
pasangan enantiomerpasangan enantiomer
1 dan 2 enantiomer3 dan 4 juga enantiomer
Diastereomer: 1-3; 1-4; 2-3 dan 2-4
Epimers:Epimers:distereomer yang berbeda hanya distereomer yang berbeda hanya
pada satu pusat kiral sajapada satu pusat kiral saja
OH
OH
OH
OH
OH
OH OH
OH
OH
OH
OH
OH
Senyawa mesoSenyawa meso
ChiralChiral Molecules With Molecules With No Chiral CentersNo Chiral Centers
Allenes can be ChiralAllenes can be Chiral
C C C
H
CH3
C CClHC
CH3
H
ClH
Mycomycin, an antibioticMycomycin, an antibiotic
C C C
H
CH=CHCH=CHCH2CO2HCCCCHH
Nocardia acidophilus []D = -130o
PPh2
PPh2
PPh2
PPh2
(S)-BINAP (R)-BINAP
Specifying Configuration (Chirality); Cahn-Ingold-Prelog Notation
Specifies the "configuration" at each chiral center, equivalent to "cis-" and "trans-" etc.
Abbreviated rules Assign priorities to groups attached to chiral
center according to atomic # (same as Z/E rules) Compare 2nd, 3rd etc. atom from center as
necessary, look for first point of difference Multiple bonds "add up" Determine direction of rotation 1 > 2 > 3 looking
with #4 group pointing "away"
Prioritize Using Cahn-Ingold-Prelog Prioritize Using Cahn-Ingold-Prelog RulesRules
Look at atoms directly attached to chirality center a) higher atomic number = higher priority b) heavier isotopes = higher priority
If no difference at first attached atom, move along the chain until the first point of difference.
Multiple-bonded atoms are equivalent to the same number of single-bonded atoms.