Question 12.5: Convert the following condensed structures to line structure...
Convert the following condensed structures to line structures:
(a) \begin{array}{r c} \underset{|}{ \quad \; CH_3} \qquad \quad \enspace \; \\ CH_3CH_2CHCHCH_2CH_3 \\ \overset{|}{ \quad \; CH_3} \qquad \qquad \quad \enspace \end{array} (b) \begin{array}{r c} \underset{|}{\enspace \; OH}\qquad \enspace \underset{|}{Cl} \qquad \qquad \; \\ CH_3CHCH-C \; CH_2CH_3 \\ \overset{|}{ \enspace \; CH_3} \overset{|}{ \quad CH_3}\qquad \quad \> \end{array}
ANALYSIS Find the longest continuous chain of carbon atoms in the condensed structure. Begin the line structure by drawing a zigzag line in which the number of vertices plus line ends equals the number of carbon atoms in the chain. Show branches coming off the main chain by drawing vertical lines at the vertices as needed. Show all atoms that are not carbons or are not hydrogens attached to carbons.
(a) Begin by drawing a zigzag line in which the total number of ends + vertices equals the number of carbons in the longest chain (here 6, with the carbons numbered for clarity):
Looking at the condensed structure, you see CH_3 groups on carbons 3 and 4; these two methyl groups are represented by lines coming off those carbons in the line structure:
This is the complete line structure. Notice that the hydrogens are not shown, but understood. For example, carbon 4 has three bonds shown: one to carbon 3, one to carbon 5, and one to the branch methyl group; the fourth bond this carbon must have is understood to be to a hydrogen.
(b) Proceed as in (a), drawing a zigzag line for the longest chain of carbon atoms, which again contains 6 carbons. Next draw a line coming off each carbon bonded to a CH_3 group (carbons 3 and 4). Both the OH and the Cl groups must be shown to give the final structure:
Note from this line structure than it does not matter in such a two-dimensional drawing what direction you show for a group that branches off the main chain, as long as it is attached to the correct carbon. This is true for condensed structures as well. Quite often the direction that a group is shown coming off a main chain of carbon atoms is chosen simply for aesthetic reasons.