N

Figure 4-1 Structural formula for ammonia.

Figure 4-2 Structural formula for carbon dioxide.

& Notes & Figure 4-2 shows that the oxygen atoms in carbon dioxide are attached to the carbon atoms. Further, two bonds are involved in the linkage. We may say, then, that oxygen has two bonds and carbon has four bonds.

Now consider the structural formula for methane (figure 4-3). This formula shows that the hydrogen atoms are attached to the carbon atoms, a fact that would not be evident if the empirical formula CH , were used. Such is the case with all compounds. Using methane as a starter, a whole series of compounds can be represented, as shown in figure 4-4.

The 4-carbon compound butane further shows the necessity of structural formulas. Both compounds shown in figure 4-5 can be represented by the empirical formula C,H,0. They are, however, quite different compounds. The first is normal butane (n-butane), and the second is iso-butane, a substance with significantly different properties.

Figure 4-3 Structural formula for methane.

H HH HHH HHHH

H —C —H H — C—C—H H —C—C—C —H H —C—C—C—C —H

H HH HHH HHHH

methane ethane propane butane

Figure 4-4 Structural formulas for methane, ethane, propane, and butane.

HHHH

HHHH n-butane

iso-butane

Figure 4-5 Structural formulas for n-butane and iso-butane.

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