Drawing Organic Structures By Using Line-Angle Formula
When chemists draw the structure of an organic molecule, an abbreviated representation is
often used. For example, the Lewis structure and the line-angle formula for benzene (C6H6) are
shown below.
H
H
H
C
C
C
C
C
C
H
H
H
Lewis
structure
line-angle
formula
In the line-angle formula, each “stick” represents a covalent bond between two atoms. A pair
of parallel “sticks” represents a double bond between the two connected atoms. When two, three
or four “sticks” intersect, and there is no atomic symbol specified at the intersection, a carbon atom
is assumed (i.e., the atomic symbol, “C”, is not written in the line-angle formula). Thus, each carbon
atom in benzene has three covalent bonds to other carbon atoms (i.e., each carbon atom forms one
double bond and one single bond to two other carbon atoms).
Finally, each carbon atom in an organic molecule is almost always covalently bound to four
other atoms. For brevity, any covalent bonds between carbon atoms and hydrogen atoms are omitted
in the line-angle formula. Because each carbon atom must have four covalent bonds, there must be
one carbon-hydrogen (C-H) bond on each carbon atom in benzene.