Question

Consider the following three oxidation reactions. I. OH CrO3, H2SO4 OH H2O OH PCC H II. CH2Cl2 OH III. TEMPO H H2O / CH2Cl2 HW1. Specify what it is about a Jones oxidation (I) that drives the oxidation to the carboxylic acid (I)?: The Jones reagent is mixture of chromic trioxide or sodium dichromate in diluted sulfuric acid which forms chromic acid. HW2. In contrast, specify what is it about a PCC oxidation that only oxidizes the alcohol to the aldehyde and stops (II) ?: PCC is a milder version of chromic acid. So, what it does oxidise alcohols one rung up the oxidation ladder, from primary alcohols to aldehydes and from secondary alcohol to ketone HW3. Read the following excerpt from a TEMPO review article (Tojo, G. Fernandez, M.I. Oxidation of Alcohols to Carboxylic Acids A Guide to Current Common Practice, 2007 pg 82) Unlike chromic acid PCC will no oxidize ald to carboxylic acids. ?In 1987, Anelli et al. made a key contribution to TEMPO-mediated oxidations by showing that the very cheap reagent chlorine bleach (aqueous NaOCl) can function very effectively as a stoichiometric oxidant for alcohols in the presence of traces of 4-MeO-TEMPO. They established a protocol involving a reaction run at 0 C in a biphasic CH2Cl2–water mixture in the presence of excess of NaOCl, NaHCO3, KBr, and catalytic 4-MeO-TEMPO for oxidation to aldehydes. Under these conditions the oxidation to acids is quite slow. If the acid is desired, it is advisable to add a phase-transfer catalyst to speed up the oxidation.?

Consider the following three oxidation reactions.
I.
OH
CrO3, H2SO4
OH
H2O
OH
PCC
H
II.
CH2Cl2
OH
III.
TEMPO
H
H2O / CH2Cl2
HW1. Specify what it is about a Jones oxidation (I) that drives the oxidation to the carboxylic acid (I)?: The Jones reagent is mixture of chromic trioxide or sodium dichromate in diluted sulfuric acid which forms chromic acid.
HW2. In contrast, specify what is it about a PCC oxidation that only oxidizes the alcohol to the aldehyde and stops (II) ?: PCC is a milder version of chromic acid. So, what it does oxidise alcohols one rung up the oxidation ladder, from primary alcohols to aldehydes and from secondary alcohol to ketone
HW3. Read the following excerpt from a TEMPO review article (Tojo, G. Fernandez, M.I. Oxidation of Alcohols to Carboxylic Acids A Guide to Current Common Practice, 2007 pg 82) Unlike chromic acid PCC will no oxidize ald to carboxylic acids.
?In 1987, Anelli et al. made a key contribution to TEMPO-mediated oxidations by showing that the very cheap reagent chlorine bleach (aqueous NaOCl) can function very effectively as a stoichiometric oxidant for alcohols in the presence of traces of 4-MeO-TEMPO. They established a protocol involving a reaction run at 0 C in a biphasic CH2Cl2–water mixture in the presence of excess of NaOCl, NaHCO3, KBr, and catalytic 4-MeO-TEMPO for oxidation to aldehydes. Under these conditions the oxidation to acids is quite slow. If the acid is desired, it is advisable to add a phase-transfer catalyst to speed up the oxidation.?

Added by Pedro T.

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