Condensed structural formula

A condensed structural formula writes connected groups of chemical atoms compactly, omitting some explicit bond strokes. It preserves interpretable connectivity information, unlike a molecular formula that merely totals the atoms. It is one way to represent a structural formula, whose purpose is to describe how atoms are connected.^[ref]

For an original counting example,can be unrolled as $\mathrm{C}{\mathrm{H}}_3\mathrm{C}{\mathrm{H}}_2\mathrm{C}{\mathrm{H}}_2\mathrm{C}{\mathrm{H}}_2\mathrm{C}{\mathrm{H}}_2\mathrm{C}{\mathrm{H}}_3$. The two terminal groups supply two carbons and six hydrogens; four interior groups supply four carbons and eight hydrogens. Thus the molecular formula is ${\mathrm{C}}_6{\mathrm{H}}_{14}$, since $2+4=6$ and $6+8=14$. The parentheses abbreviate a connected repeated group, rather than introducing a separately floating molecule.

The compression must be interpreted with the chosen convention. A formula such as $\mathrm{C}{\mathrm{H}}_3\mathrm{C}{\mathrm{H}}_2\mathrm{OH}$ specifies different connectivity from $\mathrm{C}{\mathrm{H}}_3\mathrm{OC}{\mathrm{H}}_3$ despite their common atom counts. Neither expression by itself gives every bond angle or a unique three-dimensional conformation; those questions involve molecular geometry and stereochemistry.