Alcohol Oxidation: Aldehydes, Ketones, and Carboxylic Acids

Introduction

• Alcohols: Carbon chain (R group) bound to an OH (hydroxy) group.
• Oxidation: Increasing the number of bonds between carbon and oxygen, removing hydrogen atoms.

Primary Alcohols

• Example: 1-butanol
• Structure: Carbon with OH, bound to another carbon and 2 hydrogen atoms.
• Oxidation Process:
  • First Oxidation: Remove hydrogen from OH and one hydrogen from carbon; forms a carbonyl group (aldehyde).
  • Second Oxidation: Add second oxygen; forms a carboxylic acid.
• Reagents:
  • Chromium-based: Chromic acid (H2CrO4), sodium dichromate (Na2Cr2O7), potassium dichromate.
  • Jones Reagent: Chromium trioxide (Cr3) + sulfuric acid in acetone forms chromic acid.
  • Potassium Permanganate (KMnO4): Another strong oxidizing agent.

Stopping at Aldehyde

• Special Reagent: PCC (Pyridinium Chlorochromate)
  • Structure: Pyridinium (conjugate acid of pyridine) + chlorochromate (CrO3 bound to Cl).
  • Function: Weakens oxidation, stops at aldehyde, doesn't proceed to carboxylic acid.

Secondary Alcohols

• Structure: OH bound to a secondary carbon with one hydrogen.
• Oxidation Process:
  • Single Oxidation: Remove one hydrogen from carbon and one from oxygen; forms a ketone.
• Reagents: Can use strong oxidizers like KMnO4 or chromic acids, and PCC.

Tertiary Alcohols

• Example: 2-methyl-2-butanol
• Structure: Carbon with OH attached to three other carbons, no hydrogen atoms.
• Reactivity: No oxidation possible due to lack of hydrogen; would violate the octet rule.
• Exam Tip: Write "N/R" for no reaction.

Conclusion

• Next video: Mechanisms for oxidation reactions with KMnO4, PCC, and Chromic Acid.
• Resources: Redox practice quiz and cheat sheet available at leah4sci.com/redox.

These notes cover the key reactions and reagents involved in alcohol oxidation and provide an overview of how primary, secondary, and tertiary alcohols behave under different oxidative conditions.