Lactones are cyclic esters. Under suitable conditions, lactones form from molecules that have both an alcohol and a carboxylic acid functional group. Equation 1 shows an example of the formation of a lactone. [Equation 1 showing a molecule with -OH and -COOH forming a lactone and H₂O] Fig. 5.1 shows the synthesis of lactone P from compound M. [Figure 5.1 showing reaction scheme: M --(KMnO4)--> N(C6H10O3) --(NaBH4)--> 5-hydroxyhexanoic acid --(reaction 3)--> P]