Establishing the Regioselectivity of a Small-Scale Alkene Hydration Reaction Using TLC Co-spotting

We report a small-scale, one-pot modification of a popular multigram experiment aimed at establishing the regioselectivity of 1-hexene hydration under acid conditions. Students treat 1 mL of 1-hexene with 2 mL of 84–85% w/w H2SO4 to produce a mixture of sulfate esters that, upon treatment with room-temperature water in the same flask, affords a mixture of 2- and 3-hexanol, the latter formed by a carbocation rearrangement. After a brief test-tube-scale extractive workup, students TLC co-spot their undistilled product mixture versus authentic samples of 1-, 2-, and 3-hexanol to establish the presence of both 2- and 3-hexanol as the major and minor products, respectively, and the absence of 1-hexanol. Scaling down the reaction, running it at room temperature, and using TLC instead of distillation for product identification permits students to establish the formation of both 2-hexanol (bp 136 °C) and 3-hexanol (bp 135 °C)─impossible by distillation─and complete the experiment well within a 3 hour lab period.