Cyclopropane is an interesting hydrocarbon. Instead of having three carbons in a row, the three carbons form a ring, as shown in this perspective Figure 2 (see Figure 1.1 and Figure 1.2 for a prior example of this kind of drawing): Figure 1.1 Figure 1.2 Figure 2 Cyclopropane was at one time used as an anesthetic, but its use was discontinued, in part because it is highly inflammable, (a) What is the empirical formula of cyclopropane? How does it differ from that of propane? (b) The three carbon atoms are necessarily in a plane. What do the different wedges mean? (c) What change would you make to the structure shown to illustrate chlorocyclopropane? Are there isomers of chlorocyclopropane?
Solution Step 1 : Cyclopropane is a cycloalkane molecule with the molecular formula C H . It consists of3 6 three carbon atoms linked to each other to form a ring, with each carbon atom bearing two hydrogen atoms. Step 2: (a) What is the empirical formula of cyclopropane How does it differ from that of propane In chemistry, the emp irical formula of a chemical compound is the simplest positive integer ratio of atoms present in a compound. The smallest whole number ratios of the subscripts of molecular formula are derived by dividing the subscripts by largest common factor. For example: the mpirical formula of disulfur dioxide is S O . 2 2 the mpirical formula of ethane(C H ) w2l6e CH . 3 Now, let’s write the empirical formula for cyclopropane : Th e molecular formula for cyclopropane i s 3 6 . Here the ratio of atoms is in 3:2. To write the e mpirical formula, we have to first find the largest common factor that can divide the subscripts to simplest positive integer ratio. 3 is the largest common factor that can divide and henc e the empirical formula for the compound will be CH . Here the ratio2s in 1:2. Now, let’s see How does it differ from that of propane Propane is an alkane with the m olecular formula C 38 The ratio of the atoms here is already in its simplest ratio. H ence the empirical formula for p ropane is C 3 .8 Propane has same m olecular fo rmula and empirical formula but cyclopropane has different empirical formula and m olecular formula.