# Jones Oxidation Protocol for Ketones > Published on Vicena | [View on web](https://vicena.ai/wiki/jones-oxidation-protocol-for-ketones-_-a9Ww) --- ## User What is the detailed protocol for Jones oxidation of a secondary alcohol to a ketone, including chromium trioxide equivalents, sulfuric acid concentration, acetone as solvent, and how to destroy excess chromium safely? --- ## Vicena The Jones oxidation is a classic method for the conversion of secondary alcohols to ketones. It utilizes "Jones reagent"—a solution of chromium trioxide ($\ce{CrO3}$) in aqueous sulfuric acid ($\ce{H2SO4}$)—typically performed in acetone. ### 1. Preparation of Jones Reagent (Standard 2.67 M Solution) The most common laboratory formulation for the reagent is the 2.67 M solution, prepared as follows: * **Components:** $\ce{26.72 g}$ of chromium trioxide ($\ce{CrO3}$) and $\ce{23 mL}$ of concentrated sulfuric acid ($\ce{H2SO4}$). * **Procedure:** Dissolve the $\ce{CrO3}$ in a minimum amount of distilled water (approx. $\ce{40-50 mL}$). Carefully add the concentrated $\ce{H2SO4}$ while cooling in an ice bath (the dissolution is highly exothermic). Once mixed, dilute the solution with distilled water to a final volume of $\ce{100 mL}$. * **Result:** This yields a deep orange-red solution where the active oxidant is chromic acid ($\ce{H2CrO4}$). ### 2. Reaction Protocol * **Substrate Solution:** Dissolve 1 equivalent of the secondary alcohol in acetone. The volume of acetone is typically $\ce{10-20 mL}$ per gram of substrate to ensure the resulting chromium salts remain as a manageable slurry. * **Stoichiometry:** Theoretically, 2 equivalents of $\ce{Cr(VI)}$ are required to oxidize 3 equivalents of alcohol. In practice, the reagent is added dropwise to the stirred acetone solution at $\ce{0 °C}$ to $\ce{20 °C}$. * **Endpoint:** The reaction is self-indicating. The reagent is added until the orange color of the $\ce{Cr(VI)}$ persists for 15–20 minutes, indicating that the alcohol has been fully consumed. During the reaction, the solution will turn from orange to a dark green/blue-green color, characteristic of $\ce{Cr(III)}$ salts. ### 3. Quenching and Destruction of Excess Chromium Because $\ce{Cr(VI)}$ is highly toxic and carcinogenic, any excess must be reduced to the less toxic $\ce{Cr(III)}$ state before workup. * **Isopropanol Quench:** Add isopropyl alcohol (2-propanol) dropwise to the reaction mixture. The isopropanol reacts with the remaining Jones reagent to form acetone and green $\ce{Cr(III)}$. Continue adding until the orange/brown tint completely disappears and only a green precipitate or solution remains. * **Sodium Bisulfite Quench:** Alternatively, an aqueous solution of sodium bisulfite ($\ce{NaHSO3}$) or sodium metabisulfite ($\ce{Na2S2O5}$) can be added. These inorganic reducing agents rapidly convert $\ce{Cr(VI)}$ to $\ce{Cr(III)}$. ### 4. Workup and Safety * **Workup:** After quenching, the mixture is often filtered through a pad of Celite to remove the bulky chromium salts. The filtrate is then concentrated, and the ketone is extracted using an organic solvent (e.g., diethyl ether or ethyl acetate), followed by washes with saturated $\ce{NaHCO3}$ to neutralize any residual acid. * **Safety Note:** Chromium(VI) compounds are potent oxidizers and known human carcinogens. All manipulations should be performed in a fume hood with appropriate PPE (nitrile gloves, lab coat, and safety goggles). Chromium waste must be collected and disposed of according to hazardous heavy metal protocols. For specific experimental variations, such as the synthesis of cycloöctanone or nortricyclanone, historical procedures can be found in [Organic Syntheses](http://allchemist.blogspot.com/2011/11/jones-oxidation-cro3-h2so4.html). ---