ORGANIC CHEMISTRY 354

**STEREOCHEMISTRY**

MIRROR IMAGES

SUPERIMPOSABLE

NONSUPERIMPOSABLE

ENANTIOMERS

PREDICTING CHIRALITY

PLANE OF SYMMETRY

OPTICAL ACTIVITY

PASTEUR'S DISCOVERY

MIRROR IMAGES

HANDNESS ANIMATION (CHIRALITY)

(Developed by Thomas Poon, Colby College and requires Shockwave plugin.)

SUPERIMPOSABLE

NONSUPERIMPOSABLE

ENANTIOMERS

MOLECULES WHICH ARE NOT SUPERIMPOSABLE ON THEIR MIRROR IMAGES ARE CALLED ENANTIOMERS.

ENANTIOMER IS THE NAME FOR THIS SPECIAL KIND OF STEREOISOMER.

CHIRALITY IS THE NAME FOR THE PROPERTY THESE MOLECULES HAVE.

THE MOLECULES BELOW REQUIRE CHIME PLUGIN. ADJUST THE FIRST TWO TO DEMONSTRATE THAT THEY ARE ENANTIOMERS. IS THE THIRD THE SAME AS THE LEFT OR RIGHT MOLECULE?

HOW DO YOU PREDICT IF MOLECULES ARE CHIRAL?

LOOK FOR A PLANE OF SYMMETRY.

LOOK FOR FOUR (4) DIFFFERENT GROUPS ATTACHED TO ONE CARBON.

OPTICAL ACTIVITY

OPTICAL ACTIVITY ANIMATION

(Developed by Thomas Poon, Colby College and requires Shockwave plugin.)

OPTICALLY ACTIVE MOLECULES ROTATE THE PLANE OF PLANE POLARIZED LIGHT

SOME MOLECULES ROTATE PLANE POLARIZED LIGHT TO THE LEFT (COUNTERCLOCKWISE) AND ARE SAID TO BE LEVOROTATORY (-).

SOME MOLECULES ROTATE PLANE POLARIZED LIGHT TO THE RIGHT (CLOCKWISE) AND ARE SAID TO BE DEXTROROTATORY (+).

PASTEUR'S DISCOVERY (1849)

RECRYSTALLIZED A CONCENTRATED SOLUTION OF SODIUM AMMONIUM TARTRATE BELOW 28^o

ORIGINAL SOLUTION WAS OPTICALLY INACTIVE

TWO KINDS OF CRYSTALS PRECIPITATED OUT

CRYSTALS WERE MIRROR IMAGES OF EACH OTHER

SEPARATED CRYSTALS INTO TWO TYPES USING TWEEZERS

CRYSTALS HAD SAME MELTING POINTS, SOLUBILITIES, ETC., ETC.

HOWEVER, THEY ROTATED PLANE POLARIZED LIGHT BY THE SAME AMOUNT BUT IN OPPOSITE DIRECTIONS.

PASTEUR CONCLUDED: THE DEXTRO MOLECULE EXISTS IN AN ASYMMETRIC ARRANGEMENT AND THE LEVO MOLECULE IS IT'S PRECISE INVERSE ARRANGEMENT.

NOTE: STRUCTURAL THEORY OF MOLECULES HAD NOT YET BEEN DEVELOPED.

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