TERECEMITRY CIRALITY A A C C B C D D C B
Chirality - tereoisomers 2
Chirality Enantiomers - molecules that are not superimposable on their mirror image. Molecules that can exist as enantiomers are called Chiral Molecules. Molecules that have a plane of symmetry are not chiral (achiral). tereogenic Carbons are those that have four different groups attached. 3
Biomolecules are Chiral Carbohydrates / ugars Glucose DNA Amino Acids / Proteins 2 N R 4
Chirality in mell and Taste Mirror image molecules (enantiomers) interact with chiral receptors in our nose differently. (R)-(-)-Carvone spearmint oil ()-(+)-Carvone caraway seed oil (R)-(+)-Limonene orange citrus ()-(-)-Limonene turpentine/lemon 5
Chiral Molecules in Enzymes N Me N N 6
The Case of Thalidomide stereogenic carbon N * N (R)-thalidomide beneficial sedative stereogenic carbon N * N ()-thalidomide causes birth defects 7
Tartaric Acid 1849 - Louis Pasteur separated mirror image crystals of sodium ammonium tartrate. * * Na N 4 * * 8
Louis Pasteur I found...that the tartrate was hemihedral..., but strange to say the paratartrate was hemihedral also. nly the hemihedral faces which in the tartrate were all turned the same way, were, in the paratartrates inclined sometimes to the right and sometimes to the left... I carefully separated the crystals that were hemihedral to the right from those hemihedral to the left, and examined their solutions separately in the polarizing apparatus. I then saw with no less surprise than pleasure that the crystals hemihedral to the right deviated the plane of polarization to the right, and that those hemihedral to the left deviated it to the left; and when I took an equal weight of each of the two kinds of crystals, the mixed solution was indifferent towards the light in consequence of the neutralization of the two equal and opposite individual deviations. 9
ptical Activity Enantiomers have identical physical properties mp, bp, spectroscopic, absorptions, etc. BUT they are different when interacting with plane-polarized light light travels in waves but oscillates in all three dimensions along the path of travel Light is polarized and oscillates in a single dimension when the polarized light passes through a chiral sample, it is bent out of the original plane Note that the enantiomer will bend the light in the opposite direction chiral sample chiral sample enantiomer polarizing filter 10
ptical Activity Amount of rotation depends on how many molecules the light interacts with. Light at 589 nm (odium D line) tandardized for unit cell and concentration [α]d = observed rotation ( ) cell length (dm) x conc. (g/ml) 11
Racemates...when I took an equal weight of each of the two kinds of crystals, the mixed solution was indifferent towards the light in consequence of the neutralization of the two equal and opposite individual deviations. Racemic Mixture - 50/50 mixture of enantiomers. hows N optical activity. light travels in waves but oscillates in all three dimensions along the path of travel Light is polarized and oscillates in a single dimension when the polarized light passes through a chiral sample, it is bent out of the original plane Note that the enantiomer will bend the light in the opposite direction chiral sample chiral sample enantiomer polarizing filter 12
CIP Rules for R & Configuration Rectus - Right, inister - Left 4 Cl 1 1 Cl 4 3 2 (R)-2-chlorobutane 2 3 ()-2-chlorobutane 13
R & Configuration N 2 sphingosine N 2 R R 14
R & Configuration 2 N C 3 N alanine proline 15
R & Configuration R glucose R 16
Diastereomers Diastereomers - stereoisomers that are not mirror images TEREIMER DIATEREMER ENANTIMER 17
cis/trans Diastereomers Although not optically active (not chiral), cis/trans isomers are a form of diastereomer. They differ only in their arrangement in 3-dimensions but are not mirror images. 18
configurational Diastereomers ENANTIMER R R DIATEREMER R DIATEREMER 19
ME compounds Meso Compounds are molecules that contain stereogenic carbons, but are not chiral. Their mirror images are identical. This occurs when there is a plane of symmetry in the molecule. R R IDENTICAL 20
IMER IMER (same number and kind of atoms, but are different molecules) Constitutional (bonded differently) tereoisomers (nly different in 3-dimensional arrangement) Enantiomers (mirror images) Diastereomers (not mirror images) Configurational cis/trans 21