Chapter 24, Problem 24.14YT

Interpretation Introduction

Interpretation:

The curved arrows for the given mechanism are to be drawn.

Concept introduction:

The electron movement in $\left[\text{4+2}\right]$ cycloaddition involves five atoms, three atoms from one of the reacting species (in this case, ${\text{OsO}}_{\text{4}}$) and two atoms from the other (in this case, the alkene). As a result, two of the six electrons moving cyclically end up as a lone pair on the middle of the three atoms contributed from one reacting species (in this case, the $\text{Os}$ atom from ${\text{OsO}}_{\text{4}}$). An older method of producing $\text{cis-1, 2-diols}$ involves treating an alkene with a cold, basic solution of potassium permanganate (${\text{KMnO}}_{\text{4}}$). It is not very synthetically useful, however, because the yields are typically low and the diol product can be further oxidized by ${\text{KMnO}}_{\text{4}}$.