Chapter 12, Problem 12.12YT

Interpretation Introduction

Interpretation:

To draw the alcohol that is produced on treatment with a basic solution of ${\text{H}}_{\text{2}}{\text{O}}_{\text{2}}$.

Concept introduction:

An alkene that has undergone hydroboration treatment with a basic solution of ${\text{H}}_{\text{2}}{\text{O}}_{\text{2}}$ produces alcohol. Under basic conditions, there is an equilibrium amount of deprotonated peroxide, HOO^-, called the hydroperoxide ion. The mechanism begins with coordination of HOO^- to the electron-deficient B atom of the trialkylborane, thereby producing an unstable tetrahedral intermediate. In Step 2, the breaking of a weak peroxide (O-O) bond drives a 1, 2-alkyl shift that yields a borate ester. This pair of steps occurs twice (Steps 3–6), resulting in a trialkylborate ester. In Step 7, hydroxide anion (HO^-) coordinates to the B atom of the trialkylborate ester, and in Step 8, heterolysis occurs to liberate an alkoxide anion (RO-) leaving group. In Step 9, the strongly basic alkoxide anion gains a proton from ${\text{H}}_{\text{2}}\text{O}$ to produce the first equivalent of the final alcohol. This trio of steps is then repeated twice.