Chapter 15The Three-Dimensional

Shape of Molecules

CHEM 2124 – General Chemistry II

Alfred State College

Professor Bensley

Learning Objectives Recognize whether a molecule is chiral or

achiral. Identify chirality centers. Draw two enantiomers in three dimensions

around the chirality center. Explain why some chiral drugs have very

different properties from their mirror images. Draw Fischer projection formulas. Recognize the difference between

enantiomers and diastereomers. Explain the relationship between the shape

and odor of a molecule.

3-D Molecules

A. Isomers

B. Constitutional Isomers

C. Stereoisomers

1. Cis and trans molecules

I. Review

3-D MoleculesII. Chirality

Achiral example

Which of the following objects are chiral?

3-D Molecules

•A carbon atom with four different groups like CHBrClF is called a chirality center.

3-D MoleculesIII. Enantiomers and Chirality Centers

Drawing a Pair of Enantiomers

HOW TO Draw Two Enantiomers of a Chiral Compound

Example Draw two enantiomers of 2-butanol in 3Daround the chirality center.

•Is C1 a chirality center?

3-D Molecules•Is C3 a chirality center:

Focus on Health & MedicineThe Unforgettable Legacy of Thalidomide

•The anti-nausea drug thalidomide, which was given to pregnant women in the early 1960’s had a chirality center.

•A racemic mixture is an equal mixture of two enantiomers.

3-D MoleculesIV. Racemic Mixtures

3-D MoleculesV. Fischer Projections

3-D MoleculesVI. Multiple Chirality Centers (Stereocenters)

VII. Optical Activity / Specific Rotation

3-D Molecules