Oxidation
Oxidation of a secondary alcohol gives a ketone.
- Reagents
- acidified K2Cr2O7
- Conditions
- heat under reflux
- Reaction class
- oxidation
- Equation
- R-CHOH-R' + [O] -> R-CO-R' + H2O
Overview
Oxidation of a secondary alcohol gives a ketone.
Transformation
- Equation
- R-CHOH-R' + [O] -> R-CO-R' + H2O
- Reagents
- acidified K2Cr2O7
- Environment
- heat under reflux
- Reaction class
- oxidation
- Mechanism
- oxidation
- Evidence level
- textbook core
Reference procedure
Microscale reaction check: alcohol oxidation
Propan-2-ol + acidified dichromate(VI)
Materials and quantities
- Potassium dichromate(VI) solution — 0.1 mol dm⁻³, about 2 cm³
- Sulfuric acid — 1 mol dm⁻³, about 1 cm³
- Propan-2-ol — 2 drops for the reaction well
- One unreacted acidified dichromate well — control
Apparatus
- 24-well plate
- 5–10 cm³ measuring cylinder
- Glass rod
- Dropping pipettes
- Eye protection
Procedure
- Mix approximately 2 cm³ of 0.1 mol dm⁻³ potassium dichromate(VI) with about 1 cm³ of 1 mol dm⁻³ sulfuric acid.
- Place 10 drops of the acidified dichromate mixture into the reaction well and 10 drops into a separate control well.
- Add 2 drops of propan-2-ol to the reaction well only.
- Observe the reaction and control over 15 minutes.
Critical controls
- Potassium dichromate(VI) is toxic and a chromium(VI) hazard; use the specified microscale quantities, eye protection and the institution's disposal procedure.
- This method distinguishes reactivity; it must not be presented as a preparative ketone isolation.
Practical techniques
Controlled comparison of reaction times
Compare a visible change while keeping variables other than the one under study consistent.
Setup
- Use equal concentrations, volumes and mixing methods, and equilibrate samples at the same temperature.
- Define the visible endpoint before starting and record repeated measurements.
Operating checks
- Precipitation time includes mixing and detection thresholds; its inverse is only a relative-rate proxy under matched conditions.
- Do not compare different carbon skeletons when isolating the effect of halogen identity.
Infrared evidence for functional-group change
Use functional-group absorptions and the fingerprint pattern to test a proposed transformation.
Setup
- Check sample identity, background and axis units before assigning absorptions.
- Compare the starting material and product: oxidation may introduce C=O while removing an alcohol O–H feature.
Operating checks
- Water, solvent and unreacted substrate can contribute bands.
- A carbonyl band alone does not distinguish every aldehyde, ketone, acid and ester. Use reference data and complementary evidence; no simulated trace is a measurement.
Scope and limitations
- Scope
- Secondary alcohols are oxidised to ketones.
- Limitations
- Tertiary alcohols do not follow this route under these standard oxidising conditions.
Related reactions
- Cyanohydrin formation: Ketones → Hydroxynitriles
Cyanide addition to a ketone forms a hydroxynitrile, adding a second carbonyl route into the expanded organic network.
- Oxidation: Alcohols → Ketones
Oxidation of a secondary alcohol gives a ketone.
- Reduction: Ketones → Secondary alcohols
Reduction of a ketone gives a secondary alcohol.
- Carbonyl addition: Grignard reagents → Secondary alcohols
Grignard addition to aldehydes gives secondary alcohols after work-up.
- Grignard addition co reactant: Aldehydes → Secondary alcohols
Aldehydes plus Grignard reagents give secondary alcohols after acidic work-up.
- Grignard addition co reactant: Ketones → Tertiary alcohols
Ketones plus Grignard reagents give tertiary alcohols after acidic work-up.
References
- Pearson Edexcel Level 3 Advanced GCE in Chemistry specificationPearson Education Limited · Pearson qualifications · 2024
Supports the textbook-core organic reaction routes used for displayed route and mechanism content.
- A microscale oxidation of alcoholsRoyal Society of Chemistry and Nuffield Foundation · RSC Education
Provides a controlled microscale acidified dichromate reaction check for primary, secondary and tertiary alcohols; products are not isolated.
- Rates of hydrolysis: practical videos for 16–18 studentsRoyal Society of Chemistry · RSC Education
Water is the nucleophile in the silver-nitrate comparison, and silver-halide precipitation measures released halide indirectly.
- Infrared spectroscopy: introductionRoyal Society of Chemistry · RSC Education
Molecular vibrations, functional-group absorptions and fingerprint comparison; no fabricated sample spectra.