Ch_322b_12.05

Ch_322b_12.05 - The Jones Oxidation The Jones oxidation is...

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Oxidation of Secondary Alcohols to Ketones Secondary alcohols are easily oxidized to ketones by a variety of reagents with good yields. R- CH- R' OH [O] R- C -R' O = secondary alcohol ketone Chromium VI Reagents Common oxidants are chromium VI reagents such as potassium dichromate (K 2 Cr 2 O 7 /H 2 SO 4 ), sodium dichromate (Na 2 Cr 2 O 7 /H 2 SO 4 ), and chromium trioxide (CrO 3 /H 2 SO 4 ) . In sulfuric acid solution, all of these reagents yield chromic acid (H 2 CrO 4 ) that is the actual oxidant. Stoichiometry 3 RCHR' OH + 2 H 2 CrO 4 + 6 H + 3 RCR' O + 2 Cr 3+ 8 H 2 O These oxidations typically are fast and can be carried out at, or just above, room temperature. Because of the rapid oxidation, and the very distinctive color change during the redox reaction as Cr VI ( orange) changes to Cr III ( green ), the oxidant solution can be slowly titrated into the reaction mixture until one equivalent has been added.
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Unformatted text preview: The Jones Oxidation The Jones oxidation is a mild variation of this oxidation where chromium trioxide (CrO 3 ), a red solid, is used in aqueous acetone as the solvent at room temperature. Examples OH cyclohexanol Na 2 Cr 2 O 7 H 2 SO 4 OH cyclooctanol CrO 3 H 2 O, acetone Tertiary Alcohols Tertiary alcohols are not oxidized under these conditions. They do form chromate esters with chromic acid, but no further reaction takes place. R-C-R'' R' OH tertiary alcohol HOCrOH O = O + R-C-R'' R' O CrOH O + H 2 O no further reaction Summary of Oxidation Reactions alcohol reagent product RCH 2 OH PCC RCH 2 OH H 2 CrO 4 /H 2 SO 4 KMnO 4 /HO-/H 2 O RCHR' OH H 2 CrO 4 /H 2 SO 4 CrO 3 /H 2 O, acetone RCR" R' OH no oxidation RCH O = RCO 2 H RCR' O...
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This note was uploaded on 10/20/2009 for the course CHEM 322BL at USC.

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Ch_322b_12.05 - The Jones Oxidation The Jones oxidation is...

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