Isomerism

From WikidChem

Isomerism Wohler performed analysis on many chemical compounds. He found that some of them had the same chemical composition but different properties.

One example of this kind of pair is fuminic acid and cyanic acid.

There are four different C's of chemicals: Composition, Constitution, Configuration, Conformation.

Composition is the amount of each element that goes into each chemical. Isomers have the same Composition.

Constitution is how the atoms are linked in a molecule. {the formal definition is "the nature and sequence of bonds" - JMM} Constitutional isomers have differing constitutions.

The latter two have not been covered yet in class.

The exact experiment that directed Brezelius to coin the term "isomerism" was his analysis of tartaric and racemic acids in 1830 (one year before Liebig published his paper on the use of the Kaliapparat). In the analysis of racemic acid, Brezelius found the organic percentages by weight of H, C, and O to be 3.0045, 36.8060, and 60.1895, respectively. Since these percentages were identical for tartaric acid, Brezelius had no problem using the same chemical formula to express them. In choosing the term "isomeric," which means put together from the same pieces, Brezelius COULD have used "homosynthetic," which means equivalently put together. He chose isomeric only because it was shorter and, to him, more euphonic. All said and done, isomeric substances posess the same chemical composition and atomic weights, but different properties.

NZG