Oxidation of Alcohols to Aldehydes, Ketones, and Acids Cheat Sheet

Key Facts

• A primary alcohol oxidizes first by $\mathrm{RCH_2OH + [O] \rightarrow RCHO + H_2O}$ to form an aldehyde.
• With excess strong oxidant, a primary alcohol continues by $\mathrm{RCHO + [O] \rightarrow RCOOH}$ to form a carboxylic acid.
• A secondary alcohol oxidizes by $\mathrm{R_2CHOH + [O] \rightarrow R_2C{=}O + H_2O}$ to form a ketone.
• A tertiary alcohol usually does not oxidize under normal classroom conditions because the carbon attached to $\mathrm{OH}$ has no $\mathrm{C-H}$ bond.
• Mild, anhydrous oxidants such as $\mathrm{PCC}$ are used to stop primary alcohol oxidation at the aldehyde stage.
• Strong oxidants such as acidified $\mathrm{K_2Cr_2O_7}$ or $\mathrm{KMnO_4}$ often convert primary alcohols fully to carboxylic acids.
• Oxidation of an organic molecule usually increases its number of $\mathrm{C-O}$ bonds or decreases its number of $\mathrm{C-H}$ bonds.
• The carbonyl group in aldehydes and ketones is written as $\mathrm{C{=}O}$, while the carboxyl group in acids is written as $\mathrm{COOH}$.

Vocabulary

Oxidation

Oxidation is a reaction that increases bonding to oxygen, decreases bonding to hydrogen, or raises the oxidation state of carbon.

Primary alcohol

A primary alcohol has the $\mathrm{OH}$ group on a carbon attached to only one other carbon, often written as $\mathrm{RCH_2OH}$.

Secondary alcohol

A secondary alcohol has the $\mathrm{OH}$ group on a carbon attached to two other carbons, often written as $\mathrm{R_2CHOH}$.

Tertiary alcohol

A tertiary alcohol has the $\mathrm{OH}$ group on a carbon attached to three other carbons, often written as $\mathrm{R_3COH}$.

Aldehyde

An aldehyde is a carbonyl compound with the group $\mathrm{RCHO}$ at the end of a carbon chain.

Ketone

A ketone is a carbonyl compound with the group $\mathrm{R_2C{=}O}$ within a carbon chain.