Structural isomers and drawing organic formulae

Structural isomers and drawing organic formulae

Organic formulae can be displayed, condensed or skeletal, but each representation must preserve connectivity. A displayed formula shows every bond; a condensed formula groups atoms; a skeletal formula uses line ends and vertices for carbon atoms, with hydrogens on carbon implied. Structural isomers have the same molecular formula but different connections. To generate isomers systematically, vary the parent-chain arrangement, functional-group position or functional-group type while checking valence and atom count. Avoid inventing structures that give carbon five bonds or change the total hydrogen count.

Work it through

For C₃H₈O, one valid isomer is propan-1-ol and another is propan-2-ol; both have an OH group in different positions. Methoxyethane also has C₃H₈O but a different functional group arrangement. The molecular formula is the check, while the bond connections determine whether the drawing is genuinely new.

Mastery target

Translate between organic formula representations, generate valid structural isomers and verify each by carbon count, hydrogen count and valence.