Structural, Condensed, and Line Formulas

Electron dot formulas are useful for deducing the stmctures of organic molecules, but it is more convenient to use simpler representations—structural or graphical formulas—in which a line is used to denote a shared pair of electrons. Because each pair of electrons shared between two atoms is equivalent to a bond order of 1, each shared pair can be represented by a line between the symbols of the elements. Unshared electrons on the atoms are often not shown in this kind of representation. The resulting representations of molecules are called structural 

To see the efficiency of this representation, write out both this condensed formula and the structural formula for this compound and compare the effort that it takes. 

For even greater convenience in representing the structures of organic compounds, particularly in printed material, line formulas are used, so-called because they are printed on one line. In line formulas, the symbol for each carbon atom is written on a line adjacent to the symbols for the other elements to which it is bonded. Line formulas show the general sequence in which the carbon atoms are attached, but to interpret them properly, the permitted total bond orders for all the respective atoms must be kept in mind. Again referring to compounds (a) to (e) described in Example 18.1, the line formulas are as follows  

If the permitted total bond orders of the respective atoms are remembered, it is apparent that the line formula 

EXAMPLE 18.2. Write structural and condensed formulas for the molecules represented by the following formulas  

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