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Ch. 5 - ChiralityWorksheetSee all chapters
All Chapters
Ch. 1 - A Review of General Chemistry
Ch. 2 - Molecular Representations
Ch. 3 - Acids and Bases
Ch. 4 - Alkanes and Cycloalkanes
Ch. 5 - Chirality
Ch. 6 - Thermodynamics and Kinetics
Ch. 7 - Substitution Reactions
Ch. 8 - Elimination Reactions
Ch. 9 - Alkenes and Alkynes
Ch. 10 - Addition Reactions
Ch. 11 - Radical Reactions
Ch. 12 - Alcohols, Ethers, Epoxides and Thiols
Ch. 13 - Alcohols and Carbonyl Compounds
Ch. 14 - Synthetic Techniques
Ch. 15 - Analytical Techniques: IR, NMR, Mass Spect
Ch. 16 - Conjugated Systems
Ch. 17 - Aromaticity
Ch. 18 - Reactions of Aromatics: EAS and Beyond
Ch. 19 - Aldehydes and Ketones: Nucleophilic Addition
Ch. 20 - Carboxylic Acid Derivatives: NAS
Ch. 21 - Enolate Chemistry: Reactions at the Alpha-Carbon
Ch. 22 - Condensation Chemistry
Ch. 23 - Amines
Ch. 24 - Carbohydrates
Ch. 25 - Phenols
Ch. 26 - Amino Acids, Peptides, and Proteins
Ch. 26 - Transition Metals
Constitutional Isomers vs. Stereoisomers
Test 1: Plane of Symmetry
Test 2: Stereocenter Test
R and S Configuration
Enantiomers vs. Diastereomers
Meso Compound
Test 3: Disubstituted Cycloalkanes
What is the Relationship Between Isomers?
Fischer Projection
R and S of Fischer Projections
Optical Activity
Enantiomeric Excess
Calculations with Enantiomeric Percentages
Non-Carbon Chiral Centers
Additional Guides
Racemic Mixture
Johnny Betancourt

Fischer projections are a 2D representation of the atomic connectivity and stereochemistry of 3D molecules. Originally developed in 1891 by Emil Fischer, they help visualize carbohydrates, amino acids, and other compounds in Organic and Biochemistry.

Fischer projections of glucoseFischer projections of glucoseHere we’ve got Fischer projections of L- and D-glucose. They’re enantiomers of each other, and there are plenty of other stereoisomers of the monosaccharide. 

The minimum variation required to be considered a stereoisomer is to swap the horizontal groups in one chiral center, so that means that glucose has tons of diastereomers.

L galactose and D galactoseL-galactose and D-galactoseGalactose, shown above, differs from glucose in the configuration of just one chiral center. It's got the same chemical formula and atomic connectivity as glucose but different stereochemistry, so it's a diastereomer. 

Visualizing the caterpillar methodVisualizing the caterpillar methodIt’s fairly straightforward to convert bondline structures to Fischer projections and vice-versa using the caterpillar method as seen above. Double checking your Fischer projection’s R and S to see if it’s been drawn properly is always good practice!

There are many other ways to represent three-dimensional molecules including the Haworth, sawhorse, and Newman projections.

Johnny Betancourt

Johnny got his start tutoring Organic in 2006 when he was a Teaching Assistant. He graduated in Chemistry from FIU and finished up his UF Doctor of Pharmacy last year. He now enjoys helping thousands of students crush mechanisms, while moonlighting as a clinical pharmacist on weekends.