This chapter focused on the mechanisms of ionic reactions, which represent the vast

Chapter 6, Problem 6.59

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This chapter focused on the mechanisms of ionic reactions, which represent the vast majority of the reactions throughout this textbook. In Chapter 17, we will explore another class of reactions, called pericyclic reactions, for which the changes in bonding can be described by electrons moving in a concerted fashion within a closed loop. For example, in the presence of an enzyme, chorismate (1) rearranges via a pericyclic reaction to produce compound 2; this is an important step in the biosynthesis of several naturally occurring amino acids. In the absence of the enzyme, a different conformation of chorismate (1a) can undergo a pericyclic reaction to yield 3 and 4 (J. Am. Chem. Soc. 2005, 127, 1295712964). The mechanism for each of these pericyclic reactions involves three curved arrows, representing the movement of six electrons, in a loop. HO H O O O O O HO H O O O O O HO H O O O O O OH O O O O O 1 1a 2 3 4 @ @ @ @ @ @ @ @ (a) Draw a concerted mechanism for the conversion of 1 S 2. (b) Describe the conformational change from 1 S 1a. (c) Draw a concerted mechanism for the conversion of 1a S 3 + 4.