Reactions that Change the Carbon Skeleton

In all of the problems in the previous section, the functional group changed its identity or location, but the carbon skeleton always remained the same. In this section, we will focus on examples in which the carbon skeleton changes. In some cases, the number of carbon atoms in the skeleton increases, and in other cases, the number of carbon atoms decreases. 

If the size of the carbon skeleton increases, then a C—C bond-forming reaction is required. Thus far, we have only learned one reaction that can be used to introduce an alkyl group onto an existing carbon skeleton. Alkylation of a terminal aUtyne (Section 10.10) will increase the size of a carbon skeleton  

Over time, we will see many other C—C bond-forming reactions, but for now, the knowledge that we have only seen one such reaction should greatly simplify the problems in this section, enabhng a smooth transition into the world of synthetic organic chemistry. 

If the size of the carbon skeleton decreases, then a C—C bond-breaking reaction, called bond cleavage, is required. Once again, we have only seen one such reaction. Ozonolysis of an alkene (or aUtyne) achieves bond cleavage at the location of the Tt bond  

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