Dihydroxylation of Cyclohexene

Dihydroxylation of Cyclohexene

Abstract

This was a microscale experiment in which cyclohexane-1,2-diol was synthesized by dihydroxylation of cyclohexene. Oxone, a persulfate mix that reacts with acetone to produce dimethydioxirane, reacts with cyclohexene to form cyclohexane-1,2-diol. Through a thin layer chromatography (TLC) analysis, it was determined that the product was cyclohexane-1,2-trans diol.

Introduction

The purpose of this experiment is to synthesize the cyclohexane-1,2-diol and determine whether it resulted in a cis or a trans diol. Oxone reacts with acetone to produce dimethyldioxirane, which in turn will react with cyclohexene to form cyclohexane-1,2-diol. The product was spotted on a TLC plate to determine the cis/trans nature of the diol in comparison to known cis and trans diol samples. Normal phase TLC is a form of solid-liquid adsorption chromatography and is an essential method in organic chemistry for rapid analysis of small samples. A properly executed TLC involves two important elements: the absorbent, or the stationary phase, and the eluting solvent, or the mobile phase. The stationary phase is attached to the TLC plate, in this case, the polar silica gel. Small amounts of each substance to be analyzed are spotted onto the absorbent with capillary tubes. The eluting solvent is poured into a beaker, and after the plate is placed into the beaker, a watch glass covers the beaker to allow the solvent to saturate the atmosphere of the beaker. The solvent then slowly moves up the TLC plate, carrying the sample substances with it. Eluting solvents must be selected based on a few key characteristics. The eluting solvent needs to be able to dissolve the solutes, all the while not competing with the solutes for the stationary phase. The solvent cannot be too polar, which would cause the solvent to bind to the absorbent and keep the solute in the mobile phase. If this happens, the samples will move up the plate rapidly, hindering the ability of the TLC to separate them into individual components. The substances travel up the absorbent at different rates due to their varying affinities for the selected absorbent. The weakly absorbed compounds will travel up the plate farther than the strongly absorbed compounds. Generally, the more polar the functional groups attached to the substance, the more strongly absorbed the substance is in the presence of a polar stationary phase. Removing the plate from the beaker and marking the solvent front completes the TLC. The plate is then dipped into an anisaldehyde stain solution and heated over a hot plate in order to visualize the spots. The individual components travel up the absorbent at varying lengths and are measured from the origin. The retention factor is then calculated by dividing the distance traveled by the individual spots over the distance traveled by the solvent, called the solvent front.

Formation of cyclohexane-1,2-diol:

Table of Reagents:

Compound Reagent

Product MW

(g/mol) Theoretical weight or volume Actual weight or volume Moles

(reagents) Equivalence

Oxone 152.20 0.40 g 0.40 g .0026 2.80

Water 18.02 2.00 mL 2.00 mL .111

Acetone 58.08 2.00 mL 2.00 mL . 0273 29.35

Cyclohexene 82.16 100.00 uL 2 drops .00093 LIMITING 1.00

HCl (conc.) 36.46 0.10 mL 2 drops ----

Ethyl Acetate 88.12 10.00 mL 10.00 mL .102

Saturated

NaHSO4 104.06 2.00 mL 2.00 mL ----

Results

Upon heating over a hot plate, the stained TLC plate