MCAT® ExamChemical and Physical Foundations of Biological SystemsMedium
A chemist is performing a synthesis reaction in which an alcohol is treated with a strong oxidizing agent, producing a carboxylic acid. Which of the following reagents is most likely being used for this transformation?
- APCC (Pyridinium chlorochromate)
- BNaBH₄ (Sodium borohydride)
- CCrO₃ in H₂SO₄ (Jones reagent)
- DLiAlH₄ (Lithium aluminum hydride)
Show answer & explanationAnswer & explanation
Correct answer: C. CrO₃ in H₂SO₄ (Jones reagent)
The oxidation of a primary alcohol to a carboxylic acid requires a strong oxidizing agent. Jones reagent (CrO₃ in H₂SO₄) is a powerful oxidizing agent capable of converting primary alcohols all the way to carboxylic acids. PCC is a milder oxidizing agent that converts primary alcohols to aldehydes and secondary alcohols to ketones, but not to carboxylic acids.
Why the other options are wrong
- A. PCC is a mild oxidizing agent that would convert a primary alcohol to an aldehyde, not a carboxylic acid.
- B. NaBH₄ is a reducing agent, converting aldehydes/ketones to alcohols.
- D. LiAlH₄ is a strong reducing agent, converting carboxylic acids, esters, aldehydes, and ketones to alcohols.
Oxidation of Alcohols
Alcohols can be oxidized to aldehydes, ketones, or carboxylic acids depending on the type of alcohol and the strength of the oxidizing agent.
- Primary alcohols can be oxidized to aldehydes (mild) or carboxylic acids (strong).
- Secondary alcohols can be oxidized to ketones.
- Tertiary alcohols are generally resistant to oxidation.
Memory trick: Primary PCC to Aldehyde; Jones for Carboxylic.