History, Definition, and Foundations of Organic Chemistry

Introduction to the Systematic Study of Organic Chemistry

• Scope and Importance: The study of organic chemistry begins by defining the scope and of the subject within the broader context of chemical science.

• Historical Context of Compounds: While organic compounds such as alcohol, vinegar, and dyes have been known throughout a long history, organic chemistry as a distinct discipline did not begin until the latter part of the eighteenth century.

• Foundational Isolation of Pure Forms: The transition to modern organic chemistry was marked by the isolation of pure chemical substances from natural sources. A primary figure in this development was the Swedish chemist Karl Wilhelm.

Early Discoveries and Key Biological Acids

• Contributions of Karl Wilhelm: In the late 18th century, Karl Wilhelm successfully isolated specific organic acids in their pure forms:

  • Citric Acid: Isolated from lemon in the 1770s.

  • Lactic Acid: Isolated from milk in the 1780s.

• Chemical Structures of Early Isolated Compounds:

  • Citric Acid: Represented as a complex carbon-based structure with multiple carboxyl groups. The skeletal formula involves:         $HOOC-CH_2-C(OH)(COOH)-CH_2-COOH$

  • Lactic Acid: Represented as an alpha-hydroxy acid with the following structure:         $CH_3-CH(OH)-COOH$

The Original Definition and Vital Force Theory

• Initial Conceptualization: The term "organic chemistry" was originally used to describe a direct relationship with living organisms. It was first conceived as the study of substances that:

  • Occurred as part of a plant or animal that is currently alive.

  • Occurred as part of a plant or animal that had once lived.

  • Were produced by a plant or an animal.

• Emergence of the Vital Force Theory: As scientists in the 18th and 19th centuries isolated an increasing number of pure substances from biological sources, they observed properties they believed were unique to these materials.

  • The Theory's Core Premise: It was hypothesized that substances derived from living organisms possessed a unique "vital force."

  • Distinction from Inorganics: This force was believed to make organic substances fundamentally different from substances obtained from non-living organisms or those of mineral origin.

• Impact on Scientific Progress: For many years, the belief that a "vital force" was mandatory to synthesize compounds found in living organisms acted as a deterrent. This idea explicitly discouraged chemists from attempting to synthesize organic compounds in a laboratory setting.

Elemental Characterization of Organic Compounds

• Common Elemental Components: Detailed scientific study eventually revealed that specific elements are consistently found within organic compounds.

• Primary Elements: The elements identified as common to all organic compounds during the early stages of the field include:

  • Carbon ($C$)

  • Hydrogen ($H$)

  • Oxygen ($O$)

  • Nitrogen ($N$)