琼斯试剂的反应机理

Jones试剂又名琼斯试剂，为选择性氧化有机化合物的试剂。能氧化仲醇成相应的酮，而不影响分子中存在的双键或叁键；也可氧化烯丙醇（伯醇）成醛。一般把仲醇或烯丙醇溶于丙酮或二氧甲烷中，然后滴入该试剂进行氧化反应，反应一般在低于室温下进行。

主要活性成分为铬酸，机理如下：

琼斯试剂氧化伯醇时一般不会停留在醛这一步，将继续氧化为酸，机理如下：

琼斯试剂氧化的一般操作步骤：

A 0.15–0.40volume of H2SO4(c) isadded over one volume of a 1.5–4.5 M solution of CrO3 in water. A fraction of the resulting redsolution is dropped over a 0.01–0.5 M stirred solution of the alcohol inacetone. The alcohol causes the reduction of the red Cr (VI) cations tochromium species with a greenish look. A complete oxidation of the alcohol in ashort time requires normally between 1.2 and 5.0 equiv. of CrO3. Whenthe reaction is finished, the oxidant is quenched by the addition of 0.1–0.4volumes of 2-propanol. If so desired, the reaction mixture can be neutralizedby the addition of saturated aqueous NaHCO3 or diluted NaOH. The resulting mixture isextracted with an organic solvent, such as EtOAc, DCM or Et2O. Thecollected organic solutions are washed with brine, dried (Na2SO4 or MgSO4).

应用实例：