The classification of chemical substances into organic and inorganic groups is a foundational concept in chemistry. This distinction is unusual because the name “organic compound” is rooted in a historical understanding that scientists have since proven incorrect. Although the term is now obsolete, it remains the label for a vast field of modern chemical study. The story of how these compounds got their name culminates in a single, paradigm-shifting experiment.
The Original Meaning: Association with Life
For centuries, chemical compounds were classified into two fundamentally different classes based on their origin. Inorganic substances were derived from the non-living mineral world, such as salts, metals, and rocks. Organic compounds, conversely, were defined as those substances that came exclusively from living organisms, including plants and animals.
This classification was tied to Vitalism, or vis vitalis (life force). Adherents posited that a special force was required to create the complex compounds found in living matter. Since this “vital force” could not be replicated in a laboratory, it was assumed that organic substances could never be synthesized artificially from inorganic precursors.
The Critical Experiment That Changed Everything
The division between organic and inorganic chemistry began to crumble in 1828 due to the work of German chemist Friedrich Wöhler. Wöhler was attempting to synthesize ammonium cyanate, an inorganic salt, by mixing solutions of silver cyanate and ammonium chloride. Upon heating the resulting solution, he was surprised to find he had created white crystals that were not ammonium cyanate.
Wöhler realized he had accidentally synthesized urea, a compound previously isolated only from the urine of mammals and considered the quintessential organic substance. The reaction involved the rearrangement of the atoms in inorganic ammonium cyanate, which is an unstable intermediate, into the structure of urea. This was the first time an organic compound had been created in a laboratory from definitively inorganic starting materials.
Wöhler’s successful synthesis of urea directly contradicted the Vitalism theory, demonstrating that a special “life force” was not necessary to construct organic molecules. This discovery effectively bridged the gap between the two classes of compounds and marked the beginning of modern organic chemistry. The experiment showed that organic substances obey the same natural laws as their inorganic counterparts.
The Modern Chemical Definition
Following the collapse of the vitalistic theory, chemists needed a new, structural basis for classifying compounds as organic. Today, an organic compound is defined as any compound that contains carbon atoms, typically bonded to hydrogen atoms, forming a hydrocarbon or its derivatives. The ability of carbon to form four stable covalent bonds and link with other carbon atoms creates the immense diversity seen in organic chemistry.
However, the historical name “organic” was retained despite the change in definition, mainly due to tradition and convenience in separating the two broad fields of study. Not all carbon-containing compounds are considered organic; a handful of simple substances are classified as inorganic exceptions. These exceptions include:
- Simple oxides of carbon (such as carbon monoxide and carbon dioxide)
- Carbonates
- Carbides
- Cyanides
The modern definition focuses on the unique bonding capabilities of carbon rather than the compound’s origin.