The structures of organic compounds are represented in several ways. The most important of these is the Lewis structure. However, if we were to write many compounds with their Lewis structure then definitely it would be very time consuming. Moreover, the bigger the size of the compound, the more painful writing its Lewis structure is. To overcome this problem, some other methods have been introduced.
The Lewis structures can be simplified by representing the two-electron covalent bond by a dash. Such a structural formula focuses on the electrons involved in bond formation.
A single dash represents a single bond, a double dash represents a double bond and a triple dash represents a triple bond. Lone pairs of electrons on heteroatoms (e.g. oxygen, halogens etc) may or may not be shown.
Complete Structural Formulae
Complete structural formulae can be further abbreviated by omitting some or all the dashes representing covalent bonds.
Condensed Structural Formulae
Identical repetitive units are put in parenthesis and subscripts are used to indicate their repetition. For example, CH3CH2CH2CH2CH2CH3 can be further condensed to CH3(CH2)4CH3. The role of parantheses is very important in condensed structural formulae. Study the following examples carefully :
Some other examples of condensed structural formulae
In Bond-line structural representation, carbon and hydrogen atoms are not shown and the lines representing carbon-carbon bonds are drawn in a zig-zag fashion. Only heteroatoms are written in bond line representation.
Bond line Formulae
The terminals in bond-line structures denote methyl (CH3) groups unless indicated otherwise by a functional group, while the line junctions denote carbon atoms bonded to appropriate number of hydrogens required to satisfy the valency of the carbon atoms.
Cyclic compounds are usually represented by bond line formulae :
Bond line Formulae
Some other examples of bond-line formulae