What to expect from an organic chemistry viva
An organic chemistry viva is an oral examination: you explain your reasoning aloud and respond to follow-up questions. There is no single international format. Your course or examining body determines the topics, timing, allowed materials and assessment rubric, so check its official guidance rather than assuming a particular station structure.
Questions commonly ask you to explain a mechanism, predict a product, compare reaction pathways, interpret spectra or defend a synthetic choice. The examiner may change a condition midway through a problem to see whether you can adapt your explanation. Knowing a reaction name is not enough: you should connect the starting material, conditions, bond changes and evidence for the product.
The practice stations below use a general platform rubric, not an official university or examination rubric. It considers chemical accuracy, reasoning, use of evidence and clarity. Use your own course’s criteria if they differ.
A practice examiner screen in MySummaries can keep those priorities visible while you work:
Caption: The practice examiner persona lists three areas to keep in view during an organic chemistry viva.
Prepare stations from your own material
Turn each lecture topic or practical into a station that requires an explanation, not just recall. A useful station has an opening prompt, a likely follow-up and a checkable chemical answer. For a reaction, prepare to state:
- The reactive functional group and the role of each reagent.
- The key bond made or broken, with electron-pair movement.
- How solvent, temperature or concentration could change the pathway.
- The product’s regio- and stereochemistry, where relevant.
- What experimental evidence would support the proposed product.
For spectra, practise a sequence: calculate the degree of unsaturation if a molecular formula is supplied; identify diagnostic features; assign signals; then check that the proposed structure accounts for all the evidence. State when a value is approximate or solvent-dependent.
A set of viva stations built from those topics could look like this:
Caption: Four practice stations pair an opening prompt with attempts and current practice scores.
Station 1: explain a carbonyl reduction
This station tests whether you can connect hydride transfer to product structure and stereochemistry. Give the product first, then explain the pathway. Avoid saying that sodium borohydride simply “adds hydrogen”: identify the nucleophilic hydride and the electrophilic carbonyl carbon.
A recorded attempt at this station might be marked like this:
Examiner
Acetophenone is treated with sodium borohydride, followed by aqueous work-up. What product forms, how does the mechanism proceed, and what stereochemical outcome do you expect?
Identifies 1-phenylethanol and reduction of the ketone to a secondary alcohol.
ImproveName the product before describing the steps.
Explains hydride attack at the carbonyl carbon and formation of an alkoxide.
ImproveShow that the C=O pi electrons move onto oxygen.
Recognises formation of a stereogenic carbon but does not explain why both faces can be attacked.
ImproveExplain that the carbonyl is planar and the reagent is achiral, so attack on either face gives a racemic mixture.
Mentions aqueous work-up but does not say that it protonates the alkoxide.
ImproveState that protonation of the alkoxide gives the alcohol.
A strong answerAcetophenone is reduced to 1-phenylethanol, a secondary alcohol. A hydride from borohydride attacks the electrophilic carbonyl carbon, and the C=O pi electrons move onto oxygen to form an alkoxide. Aqueous work-up protonates that alkoxide. The product carbon bearing OH is stereogenic. Because the carbonyl is planar and the reagents are achiral, attack on either face gives a racemic mixture.
That is a MySummaries station, filled with organic chemistry material. Yours is written from your own notes. Start free
Caption: A marked reduction answer shows a solid product prediction but a missing explanation of facial attack.
Notice the order in the model: product, electron movement, work-up, then stereochemistry. In a viva, that order makes it easier for the examiner to follow your reasoning. If asked how you would confirm the product, say that the ketone carbonyl signal should disappear and an alcohol O–H absorption should appear; exact IR positions depend on the sample and measurement conditions.
The examiner may then ask why the carbonyl carbon is electrophilic. Explain that the C=O bond is polar because oxygen is more electronegative, leaving the carbon partially positive. This is the reason a nucleophile can attack there. If you are unsure about a detail, state what you know and identify the uncertainty rather than inventing a value.
Station 2: distinguish substitution from elimination
This station tests pathway comparison. Do not promise one product from the phrase “hydroxide reacts with 2-bromobutane” alone. Conditions matter, and substitution and elimination can compete.
Aqueous hydroxide can act as a nucleophile and replace bromide. With a secondary halide, substitution may proceed by an SN2 pathway; backside attack gives inversion at the reacting stereocentre. Under strongly basic, heated conditions, elimination is favoured: hydroxide removes a beta hydrogen as the leaving group departs in an E2 step. For 2-bromobutane, elimination gives butenes, with but-2-ene generally favoured over but-1-ene; trans-but-2-ene is more stable than the cis isomer.
A full attempt should identify what additional information would help: solvent, temperature, base concentration, substrate stereochemistry and whether the question asks for the major product or all plausible products. Avoid treating “aqueous” and “ethanolic” as magic labels; explain how the conditions affect nucleophilicity, basicity and the competing pathways.
The examiner can probe stereochemistry by asking what geometry E2 requires. The beta C–H bond and leaving C–Br bond must be antiperiplanar for the concerted elimination. If the question supplies a specific stereoisomer or conformation, use that information to predict which alkene geometry is accessible. If it does not, avoid claiming a unique stereochemical result.
Station 3: identify an ester from spectra
This station tests whether you use formula, IR and NMR together rather than matching one peak in isolation. The values below are approximate: chemical shifts vary with solvent and conditions.
A recorded answer to this spectral problem might receive the following feedback:
Examiner
A compound has molecular formula C4H8O2. Its IR spectrum has a strong absorption near 1740 cm−1 and no broad O–H band. Its proton NMR has signals near 1.25 ppm (triplet, 3H), 2.05 ppm (singlet, 3H) and 4.12 ppm (quartet, 2H). Propose a structure and justify it.
Recognises one degree of unsaturation but does not show the calculation.
ImproveUse (2C + 2 + N − H − X)/2; here the result is one.
Uses the strong carbonyl absorption and absence of a broad O–H band to support an ester rather than a carboxylic acid.
ImproveConnect the absent O–H feature to the alternatives you are excluding.
Assigns the triplet and quartet to an ethyl group but does not clearly assign the singlet.
ImproveAssign the 2.05 ppm singlet to the methyl group next to the carbonyl.
Proposes ethyl acetate and checks the integrations, but does not account for all four carbons explicitly.
ImproveState that the four environments are carbonyl, OCH2, CH3CO and terminal CH3.
A strong answerThe formula gives one degree of unsaturation: (2 × 4 + 2 − 8)/2 = 1, consistent with a carbonyl. The strong absorption near 1740 cm−1 and lack of a broad O–H band support an ester rather than a carboxylic acid. The triplet and quartet with a 3:2 integration indicate an ethyl group, with the quartet at about 4.12 ppm consistent with OCH2. The 2.05 ppm singlet fits a methyl group next to a carbonyl. Together, the data support ethyl acetate, CH3COOCH2CH3.
Caption: A marked spectral answer links the formula, IR features and three proton NMR signals to ethyl acetate.
A strong viva answer also checks whether the structure accounts for every atom and signal. The formula C4H8O2 has one degree of unsaturation, accounted for by the carbonyl. Ethyl acetate has four carbon environments: the ester carbonyl, OCH2, the acetyl methyl and the terminal ethyl methyl. If a supplied spectrum contradicts your structure, revise it rather than defending a convenient first guess.
How to practise aloud
Use a repeatable routine for each station:
- Answer the question directly. Name the product, pathway or likely structure in your first sentence.
- Explain the evidence. Connect reagents and conditions to the mechanism, or connect spectral features to structural fragments.
- Make the chemistry visible. Say where the electron pair moves, which bond changes and what intermediate forms. Draw a mechanism only if your assessment permits it.
- Check alternatives. Mention a competing pathway or structure when the question leaves conditions or data ambiguous.
- Finish with a test. State one observation that could support or challenge your answer.
Record yourself for a fixed practice interval, then listen for unsupported jumps: “it forms the product” without a mechanism, “the peak means an ester” without corroborating evidence, or “the major product” without conditions. Correct one specific gap on the next attempt. Do not judge fluency alone; a smooth answer can still omit the stereochemical reason or a key signal assignment.
A transcript review can isolate a phrase that needs more chemistry:
The hydride attacks the carbonyl carbon, and the pi bond moves onto oxygen to give an alkoxide. Then it just becomes the alcohol. The carbonyl is planar, so either face can be attacked by the achiral reagent.
Then it just becomes the alcohol.
This skips the role of aqueous work-up and does not name the protonation step.
Say: Say: ‘Aqueous work-up protonates the alkoxide to give 1-phenylethanol.’Caption: A transcript review flags a vague conversion and supplies the missing work-up step.
The revision is short but chemically specific. Listen again after correcting it: can you explain the same point without memorising a whole paragraph? That is a useful test of whether you understand the sequence.
Keep a compact revision loop
After each practice session, add only the correction that will change your next answer. For a mechanism, that might be the stereochemical consequence of backside attack; for spectroscopy, it might be an integration you failed to account for. Revisit the corrected point in a later session and explain it aloud without looking at the model.
A brief examiner-style debrief can reinforce a specific point from a recorded response:
You connected the triplet and quartet to an ethyl group; now account for the singlet and the carbonyl evidence as well.
Caption: A spoken debrief points the candidate back to the unassigned NMR signal.
Do not try to memorise every possible follow-up. Prepare adaptable explanations: what makes a site reactive, what the conditions do, what evidence supports the product, and what could change the outcome. Those questions transfer across many organic chemistry topics.
How MySummaries helps
Build a revision board from your own lecture slides, PDFs or photographed notes, then turn its mechanisms, reaction conditions and spectra into flashcards. Use the board to create spoken viva stations, record an answer and review feedback against a practice rubric. You can start at portal.mysummaries.app.