Oxidation of Ethanol (to Ethanoic Acid)

Core idea

Overview

The oxidation of ethanol to ethanoic acid represents the complete oxidation of a primary alcohol through an aldehyde intermediate. In a laboratory setting, this is typically achieved by heating ethanol under reflux with an excess of an oxidizing agent such as acidified potassium dichromate(VI).

When to use: This equation is applied when modeling the full conversion of ethanol into carboxylic acids, assuming a strong oxidizing environment and sufficient heat. It is used in stoichiometry calculations for industrial vinegar production and laboratory synthesis where the intermediate ethanal is not the desired final product.

Why it matters: This reaction is the chemical basis for the production of acetic acid in vinegar and explains how wine turns sour when exposed to air. In biological contexts, it mirrors the metabolic pathway in the liver where enzymes convert toxic ethanol into ethanoic acid for excretion.

Symbols

Variables

C_2H_5OH = Ethanol, [O] = Oxygen (from oxidizing agent), CH_3COOH = Ethanoic Acid, H_2O = Water

C_{2} H_{5} O H

Ethanol

mol

[O]

Oxygen (from oxidizing agent)

mol

C H_{3} C O O H

Ethanoic Acid

mol

H_{2} O

Water

mol

Walkthrough

Derivation

Understanding the Complete Oxidation of Ethanol

Oxidation of a primary alcohol to a carboxylic acid using an excess oxidising agent under reflux.

Excess acidified K2Cr2O7/H+ under reflux.

1

State the Equation:

Dichromate changes from orange (Cr2O7^{2-}) to green (Cr^{3+}).

CH_{3} CH_{2} OH + 2 [O] \to CH_{3} COOH + H_{2} O

Result

CH_{3} CH_{2} OH + 2 [O] \to CH_{3} COOH + H_{2} O

Source: AQA A-Level Chemistry — Organic Chemistry

Visual intuition

Graph

Graph unavailable for this formula.

The graph is a straight line passing through the origin. Since ethanoicAcid is directly proportional to the amount of ethanol, increasing the ethanol concentration results in a constant, proportional increase in the acid produced.

Graph type: linear

Why it behaves this way

Intuition

Imagine the carbon atom in ethanol's -CH2OH group progressively losing hydrogen atoms and gaining oxygen atoms, transforming from an alcohol to an aldehyde (intermediate)

C2H5OH

Ethanol, a primary alcohol

The starting organic molecule that undergoes a series of transformations, losing hydrogen atoms and gaining oxygen atoms.

2[O]

Nascent oxygen, representing the oxidizing agent

The active component (e.g., from acidified dichromate or permanganate) that facilitates the removal of hydrogen atoms and addition of oxygen atoms to ethanol.

CH3COOH

Ethanoic acid, a carboxylic acid

The fully oxidized organic product, where the carbon atom originally bearing the hydroxyl group is now part of a carboxyl group (-COOH).

H2O

Water

A stable inorganic byproduct formed from the hydrogen atoms removed from ethanol and oxygen atoms supplied by the oxidizing agent.

Free study cues

Insight

Canonical usage

This equation is used to express the stoichiometric molar ratios of reactants and products, ensuring the conservation of mass and atoms in a chemical transformation.

Common confusion

A common mistake is to interpret the stoichiometric coefficients directly as mass ratios rather than molar ratios. For accurate mass calculations, molar masses must be used to convert between moles and mass.

Dimension note

The coefficients in a balanced chemical equation, such as C2H5OH + 2[O] → CH3COOH + H2O, represent the relative number of moles or molecules involved in the reaction.

One free problem

Practice Problem

If 92.14 grams of ethanol are fully oxidized in a reflux setup with excess potassium dichromate, what mass of ethanoic acid will be produced?

Ethanol92.14 mol

Solve for: ethanoicAcid

Hint: First convert the mass of ethanol to moles using its molar mass (46.07 g/mol), then use the 1:1 molar ratio to find the mass of ethanoic acid.

The full worked solution stays in the interactive walkthrough.

Where it shows up

Real-World Context

In wine turning to vinegar (oxidation by bacteria), Oxidation of Ethanol (to Ethanoic Acid) is used to calculate Ethanoic Acid Produced from Ethanol, Oxygen (from oxidizing agent), and Water. The result matters because it helps connect measured amounts to reaction yield, concentration, energy change, rate, or equilibrium.

Study smarter

Tips

Use the 1:2 molar ratio between ethanol and oxidizing oxygen atoms [O] to calculate reagent requirements.
Remember that refluxing is necessary to ensure the reaction goes to completion rather than stopping at the aldehyde stage.
The change in oxidation state of the catalyst, such as Cr(VI) to Cr(III), provides a visual indicator of reaction progress.

Avoid these traps

Common Mistakes

Distilling (gives aldehyde instead).
Wrong color change.
Forgetting water produced.

Keep going

Related Formulas

Common questions

Frequently Asked Questions

Oxidation of a primary alcohol to a carboxylic acid using an excess oxidising agent under reflux.

This equation is applied when modeling the full conversion of ethanol into carboxylic acids, assuming a strong oxidizing environment and sufficient heat. It is used in stoichiometry calculations for industrial vinegar production and laboratory synthesis where the intermediate ethanal is not the desired final product.

This reaction is the chemical basis for the production of acetic acid in vinegar and explains how wine turns sour when exposed to air. In biological contexts, it mirrors the metabolic pathway in the liver where enzymes convert toxic ethanol into ethanoic acid for excretion.

Distilling (gives aldehyde instead). Wrong color change. Forgetting water produced.