Skeletal formula

The skeletal formula, also called line-angle formula or shorthand formula, of an organic compound is a type of molecular structural formula that serves as a shorthand representation of a molecule's bonding and some details of its molecular geometry. A skeletal formula shows the skeletal structure or skeleton of a molecule, which is composed of the skeletal atoms that make up the molecule. It is represented in two dimensions, as on a page of paper. It employs certain conventions to represent carbon and hydrogen atoms, which are the most common in organic chemistry.

The technique was developed by the organic chemist Friedrich August Kekulé von Stradonitz. Skeletal formulae have become ubiquitous in organic chemistry, partly because they are relatively quick and simple to draw. They can be thought of as abbreviated Lewis structures observing the following conventions: (1) carbon atoms are indicated as the terminus of a line segment or meeting point of line segments; (2) hydrogen atoms connected to carbon are omitted, with the presumption that each carbons atom is bonded to the number of hydrogen atoms that would bring its valence to 4 (or as close to satisfying the octet rule as other electronic details allow). As in a Lewis structure, a doubled or tripled line segment indicates double or triple bonding, respectively. In contrast to a Lewis structure, however, only heteroatoms (atoms other than carbon or hydrogen) are explicitly shown, and non-bonding electron pairs are omitted.

Although Haworth projections and Fischer projections look somewhat similar to skeletal formulae, there are differences in the conventions used, which the reader needs to be aware of in order to understand the details of a molecule.

The skeletal structure of an organic compound is the series of atoms bonded together that form the essential structure of the compound. The skeleton can consist of chains, branches and/or rings of bonded atoms. Skeletal atoms other than carbon or hydrogen are called heteroatoms.

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