Chemical Formulas

Chemical Formulas & Isomers

Chemical formulas are the "blueprints" of molecules. Depending on the detail needed, we use different types of formulas to describe a substance.

Formula Types

Molecular Formula: Shows the exact number of atoms (e.g., C₆H₁₂O₆).
Empirical Formula: Shows the simplest whole-number ratio (e.g., CH₂O).
Structural Formula: Shows how atoms are connected in space.

Molecular vs. Empirical Comparison

Name	Molecular	Empirical
Ethane	C₂H₆	CH₃
Acetic Acid	C₂H₄O₂	CH₂O

Clinical Relevance: Isomers

Isomers are molecules with the same formula but different shapes. This is critical in pharmacology; often, only one "shape" of a drug molecule (one isomer) fits into a cellular receptor to provide treatment. For example the two isomers of carvone show below smell different.

Left: Caraway smell | Right: Spearmint smell

Clinical Case Study: The Shape of Thalidomide

In the health sciences, the "shape" of a molecule is often more important than its ingredients. Enantiomers are isomers that are mirror images of one another, much like a left and right hand.

The Thalidomide Tragedy

In the 1950s, Thalidomide (C₁₃H₁₀N₂O₄) was used to treat morning sickness. However, the drug contained two mirror-image isomers with vastly different effects:

🟢 R-Isomer: Effectively treated nausea and acted as a sedative.
🔴 S-Isomer: Acted as a teratogen, causing severe developmental defects in fetal limb growth.

Why this matters for Nurses:

This event led to modern "Chiral" drug development. Many medications you administer (like Albuterol or Naproxen) are now specifically manufactured to contain only the beneficial isomer to reduce side effects and toxicity.

Review/try problems 27, 29, 31, and 33