What organic chemistry practice questions should test

Organic chemistry practice questions are most useful when they require you to do something with chemical information, not merely recognise a definition. A balanced set should test whether you can:

  • identify functional groups and classify compounds;
  • apply nomenclature and constitutional or stereochemical relationships;
  • predict products from reagents and conditions;
  • explain a reaction mechanism with curly arrows;
  • compare acidity, basicity, nucleophilicity and stability;
  • interpret infrared, NMR and mass spectra;
  • design a short synthesis;
  • justify an answer using evidence rather than pattern recognition.

Do not treat a worksheet as a list of unrelated problems. Sort each question by the decision it requires. For example, “predict the major product” may test alkene stability, regioselectivity, stereochemistry or the role of the solvent. The visible question is often shorter than the reasoning needed to answer it.

A useful practice session contains questions from three levels:

  1. Recall: identify a functional group, reagent or common reaction.
  2. Application: predict a product or interpret data in a familiar setting.
  3. Transfer: solve a problem where the reaction, substrate or data set is unfamiliar.

Spend most of your time on application and transfer questions. Recall questions are useful for checking gaps, but they should not make up your whole revision method.

A repeatable method for solving questions

Use the same sequence each time. A consistent process makes it easier to locate the source of an error.

1. Read the command word

“Name”, “draw”, “predict”, “explain”, “compare” and “propose” require different answers. If the question asks for a mechanism, a product alone is incomplete. If it asks for a major product, you may need to compare competing pathways rather than list every possible product.

2. Mark the reactive features

Circle the functional group, leaving group, acidic hydrogen, unsaturation or charged atom. In a synthesis problem, mark both the starting material and the required functional group in the product. In a spectroscopy question, note the molecular formula, degree of unsaturation and all reported signals before assigning anything.

3. State the governing principle

Write a short prediction before drawing the answer. Examples include:

  • a strong nucleophile attacks an electrophilic carbon;
  • a carbonyl carbon is electrophilic;
  • a more stable carbocation is favoured in a stepwise pathway;
  • a proton is more acidic when its conjugate base is stabilised;
  • an sp² carbon cannot freely rotate around the double bond;
  • an NMR signal must account for the number and environment of hydrogen atoms.

This prevents you from choosing a reaction from visual resemblance alone.

4. Draw the complete result

Include charges, lone pairs where they matter, stereochemistry, major products and relevant by-products if requested. For mechanisms, use arrows from an electron source to an electron-poor site. Do not draw arrows from a positive atom to a bond unless the bond is the electron source being broken.

5. Check the answer

Ask whether the atom count, charge, valence and stereochemistry are consistent. For a reaction, check that the reagent can actually produce the change shown. For a spectrum, check that the proposed structure explains every significant signal and does not create signals that are absent.

High-value organic chemistry practice questions

Product prediction and reaction choice

For each reaction, write the major organic product and give one reason for your choice.

  1. Propene reacts with HBr in the absence of peroxides. What product is expected?
  2. 2-bromopropane is heated with ethanolic hydroxide. What type of reaction competes with substitution, and what alkene could form?
  3. Ethanal reacts with sodium borohydride, followed by aqueous work-up. What functional group is produced?
  4. An alkene is treated with aqueous acid. What broad transformation should you consider?

The point is not to memorise four isolated answers. For each question, identify the bond formed or broken, the reactive intermediate if one is relevant, and the feature that controls selectivity. When several products are possible, state why one is favoured rather than simply labelling it “major”.

Mechanism questions

Mechanisms are a good test of whether you understand a reaction rather than recognise its name. Practise questions such as:

  • Show the mechanism for the reaction between hydroxide and bromoethane.
  • Explain why an acyl substitution reaction can occur at a carbonyl carbon.
  • Draw the acid-catalysed addition of water to an alkene.
  • Show the initiation, propagation and termination steps for a radical reaction, if those stages are part of your course.

Before starting, identify the nucleophile, electrophile, leaving group and any catalyst. Then draw one electron movement at a time. After each step, check the formal charge and valence. A mechanism with plausible-looking arrows can still be wrong if an atom exceeds its allowed valence or a charge appears without an electron movement to explain it.

Acidity, basicity and stability

These questions are often answered too quickly. Do not compare isolated structures without drawing the relevant conjugate bases or acids.

Try questions such as:

  1. Rank ethanol, ethanoic acid and phenol by acidity, and explain the order.
  2. Which is the stronger base: an amine or an amide nitrogen? Explain how delocalisation affects the lone pair.
  3. Compare two substituted benzoic acids and predict which has the lower pKa, using the substituent effects expected in your course.
  4. Rank a set of carbocations by stability and identify the factors responsible.

Your explanation may involve resonance, inductive effects, electronegativity, aromatic stabilisation, hybridisation or solvation. Name the factor and connect it to the structure. “The electrons are more spread out” is not enough unless you show where that spreading occurs.

Spectroscopy and structure identification

Treat spectroscopy as a constraint problem. Start with information that limits the possibilities most strongly.

A useful order is:

  1. calculate the degree of unsaturation from the molecular formula;
  2. identify major infrared absorptions;
  3. count proton environments and compare integration values;
  4. use chemical shift and splitting to assign neighbouring hydrogens;
  5. check whether the proposed structure explains all observations.

Practise with incomplete information as well as full data tables. For example:

A compound has formula C₄H₈O₂. Its infrared spectrum contains a strong absorption consistent with a carbonyl group. The proton NMR contains a three-hydrogen triplet, a two-hydrogen quartet and a three-hydrogen singlet. Propose a structure and explain each signal.

Do not jump directly to a familiar ester. Calculate the unsaturation first, use the carbonyl evidence, then match integration and splitting. If a proposed structure leaves a signal unexplained, reject it even if one part appears to fit.

Synthesis and retrosynthesis

Synthesis problems become manageable when you work backwards. Mark the bond or functional group that differs between the target and a plausible precursor. Then ask which reaction can make that change and whether the starting material can be converted into the required precursor.

For each proposed route, check:

  • whether the reagents perform the stated transformation;
  • whether another functional group would react first;
  • whether the carbon skeleton is preserved or changed as required;
  • whether regioselectivity or stereochemistry creates a problem;
  • whether the route contains unnecessary steps.

Practise drawing two possible routes before selecting one. This develops reaction choice and exposes gaps in your reaction map.

How to mark your own answers

Marking should produce a correction, not just a score. For every missed question, record the first point at which your reasoning failed:

  • Recognition error: you did not identify the functional group or reaction family.
  • Rule error: you applied the wrong selectivity or stability principle.
  • Drawing error: the idea was correct, but the structure, charge or arrows were wrong.
  • Data error: you misread integration, splitting, formula or units.
  • Communication error: the answer lacked the explanation requested.

Then redo the question without looking at the solution. If you can repeat the answer but cannot explain the principle, the topic is not secure. Revisit a similar question after a delay, and later attempt a mixed question where the reaction type is not announced.

Keep an error log with four columns: question type, mistake, corrected principle and a new example. Review the principle and the example separately. This stops you memorising the exact appearance of one exercise.

Building a weekly practice set

A practical session might look like this:

  • First block: five short recall or structure questions to expose gaps.
  • Second block: three product prediction or mechanism questions, written without notes.
  • Third block: one spectroscopy or synthesis problem requiring several decisions.
  • Final block: mark the work and rewrite only the incorrect reasoning.

Mix topics once you know the individual reaction families. A mixed set forces you to decide whether a problem involves substitution, elimination, addition, oxidation, reduction, acyl chemistry or something else. That decision is part of the skill being assessed.

Use notes only after making a genuine attempt. If you consult a reaction table immediately, you may recognise the answer without learning how to select the reaction. Give yourself a defined attempt period, write down your uncertainty, then check the source and update your error log.

For a digital revision workflow, MySummaries can turn your own lecture slides, PDFs and photographed notes into a revision board, then generate practice material from that source. This is useful when your course uses particular reaction names, notation or spectroscopic conventions, but you should still verify every answer against your teaching materials and the marking guidance for your course.

How MySummaries helps

MySummaries lets you build an Organic Chemistry revision board from your own materials. From that board, you can generate flashcards for reaction conditions and terminology, written mock exams based on your notes, audio lectures for review, and live oral-exam practice. For this task, use it to create mixed organic chemistry practice questions, mark recurring errors, and return to the reactions or mechanisms you cannot yet explain without prompts.