. . Saturated and Unsaturated Carbon Compounds We have already seen the structure of methane. Another compound formed between carbon and hydrogen is ethane with a formula of C H .
In order to arrive at the structure of simple carbon compounds, the first step is to link the carbon atoms together with a single bond (Fig. .6a) and then use the hydrogen atoms to satisfy the remaining valencies of carbon (Fig. .6b). For example, the structure of ethane is arrived in the following steps – C—C Step Figure .
(a) Carbon atoms linked together with a single bond Three valencies of each carbon atom remain unsatisfied, so each is bonded to three hydrogen atoms giving: Step Figure . (b) Each carbon atom bonded to three hydrogen atoms The electron dot structure of ethane is shown in Fig. . (c).
Can you draw the structure of propane, which has the molecular formula C H in a similar manner? You will see that the valencies of all the atoms are satisfied by single bonds between them. Such carbon compounds are called saturated compounds. These compounds are normally not very reactive.
However, another compound of carbon and hydrogen has the formula C H and is called ethene. How can this molecule be depicted? We follow the same step-wise approach as above. Carbon-carbon atoms linked together with a single bond (Step ).
We see that one valency per carbon atom remains unsatisfied (Step ). This can be satisfied only if there is a double bond between the two carbons (Step ). (c) Electron dot structure of ethane