10: Organic Redox
- Page ID
- 150526
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Name: ______________________________
Section: _____________________________
Student ID#:__________________________
Organic Redox Reactions
When considering organic molecules, the oxidation state rules can often be reduced to
reduction involves gain of hydrogen or loss of oxygen oxidation is loss of hydrogen or gain of oxygen
Table of ox/red for Organic Compounds
Assume that the atoms have enough hydrogens/lone pairs to complete an octet.
Based on the rule above:
- What happens to the oxidation state of these compounds as you proceed down a column?
- Which is more oxidized?
Amine Or Nitrile
Aldehyde Or Acid
Alkane Or Alcohol
Reductions: A Mechanistic View
Review: One method for reduction of a ketone is with hydride reagents.
- Draw a hydride reduction of acetone.
- Calculate the oxidation state of the atoms in the starting material.
- Calculate the oxidation state of the atoms in the product.
- Explain why this is considered a reduction.
Review: One method for reduction of an alkene is with hydrogenation.
- Complete the catalytic cycle for the hydrogenation.
- Calculate the oxidation state of the atoms in the starting material.
- Calculate the oxidation state of the atoms in the product.
- Explain why this is considered a reduction.
Oxidations of Alcohols: Mechanistic View
There seem to be two main types of oxidations -- free radical mechanism and an ionic mechanism. For this course, we will assume all to be ionic mechanisms. In the ionic mechanism, there are two parts.
Step 1: Formation of Intermediate with a LG on the oxygen.
Step 2: E2- like Elimination of the LG
- Draw the E2 mechanisms for the following oxidations:
Oxidations of Aldehydes
The oxidation of an aldehyde to a carboxylic acid requires the formation of a hydrate in the first step.
- Draw the mechanism for the formation of the hydrate of acetaldehyde.
The hydrate is then converted to an intermediate with a leaving group on one of the oxygens.
- Draw the intermediate for the hydrate of acetone and one of oxidizing agents seen on the previous page.
- Draw the E2 mechanism for this oxidation.
One way to prevent over-oxidation of primary alcohols to carboxylic acids is to run these reactions in anhydrous conditions. See the Table on the following page for which reagents oxidize to the aldehyde and which oxidize a primary alcohol to the carboxylic acid.
Overview of Oxidizing Agents of Alcohols
- Make notecards for these reagents.
| Reagent | Product of Alcohol Oxidation |
|
PCC PDC CrO3, pyr DMSO, Oxalyl Chloride (Swern) DMP (Dess-Martin periodinane) Na2Cr2O7 CrO3, H2SO4 (Jones Reagent) KMnO4 Ag2O Ca(OCl)2 or NaOCl |
aldehyde/ketone aldehyde/ketone aldehyde/ketone aldehyde/ketone aldehyde/ketone carboxylic acid (if primary alcohol) carboxylic acid (if primary alcohol) carboxylic acid (from aldehyde) carboxylic acid (from aldehyde) carboxylic acid (if primary alcohol) |
Summary
- Predict the product for these reactions.
- Confirm that the conversion of an aldehyde to a carboxylic acid is an oxidation. Show your work.
- In the conversion of an aldehyde to the acid, determine which atom is reduced when using the following reagent:
- Na2Cr2O7
- Ag2O
- KMnO4
- Ca(OCl)2
Application Problem
Synthesis of Oxycodone
Kimishima, et. al. Org. Lett. 2014, 16, 6244-6247.
Oxycodone is a semi-synthetic analgesic prescribed for cancer pain management.
- Complete the following synthetic scheme for the synthesis.
- Identify all of the oxidation reactions in this roadmap.
- Identify all of the reduction reactions in this roadmap.