# RealOChem

> Free, unlimited chemistry practice problems — organic and general chemistry — with instant feedback on real molecular structures. No account needed. Created by Dennis Cao, an organic chemist and professor at Macalester College (BS UC Berkeley, PhD Northwestern).

Every practice page generates randomized problems from curated banks of real molecules and reactions, rendered with RDKit. Problems are interactive (click atoms, drag substituents, draw curved arrows) and graded instantly, with adjustable difficulty filters. Concept study guides pair with each practice area. Practice content is free for classroom and individual use under CC BY-NC 4.0 — see the license page.

## Study guides

- [Study guides hub](https://realochem.study/study-guides/): concise concept guides, each linked to matching practice pages (more guides are in review and publishing steadily)
- [Isomers and stereochemistry](https://realochem.study/study-guides/stereochemistry/): chirality, enantiomers vs diastereomers, meso compounds, CIP priority rules, assigning R/S and E/Z
- [pKa and acid-base chemistry](https://realochem.study/study-guides/pka/): evaluating acidity and basicity, Ka/pKa, structural effects on acid strength
- [Electrophilic aromatic substitution](https://realochem.study/study-guides/electrophilic-aromatic-substitution/): mechanism, directing effects, activating and deactivating groups

## Organic chemistry practice

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- [Determine a Molecular Formula](https://realochem.study/line-angle-reading/): Count atoms from line-angle structures and check your answer instantly.
- [IUPAC Nomenclature](https://realochem.study/IUPAC-nomenclature/): Name organic compounds systematically with personalized feedback to incorrect answers.
- [Nomenclingo (IUPAC Name Builder)](https://realochem.study/nomenclingo/): Build IUPAC names piece by piece from a structure in this interactive naming game.
- [Guided IUPAC Naming](https://realochem.study/IUPAC-nomenclature/?mode=guided): Learn the IUPAC naming algorithm step by step: identify the FG, select the parent chain, find substituents, and number.
- [Functional Group Identification](https://realochem.study/functional-groups/): Spot every functional group in a molecule before checking your answer.
- [Functional Group Classification](https://realochem.study/functional-group-detail/): Classify a highlighted functional group with its full label: modifier and base group.
- [Identify Aromaticity](https://realochem.study/aromatic/): Determine whether ring systems are aromatic, antiaromatic, or nonaromatic.
- [Compare Resonance Contributors](https://realochem.study/resonance-ranking/): Determine which resonance form is the more significant contributor.
- [Resonance Arrows](https://realochem.study/resonance-draw/): Draw curved arrows showing electron movement between resonance forms.
- [pKa Comparison (DMSO)](https://realochem.study/pKa-pairs/): Pick the more acidic compound from two structures and learn pKa values in DMSO.
- [pKa Comparison (Water)](https://realochem.study/water-pka-pairs/): Pick the more acidic compound using pKa values in water.
- [Find the Acidic Proton](https://realochem.study/acidic-proton/): Click on the most acidic atom in each molecule. Covers O–H, N–H, and C–H acids.
- [Mechanism Arrows](https://realochem.study/mechanism-draw/): Learn to draw curved arrows for common organic mechanism steps.
- [Assign R or S Stereochemistry](https://realochem.study/stereochemistry-RS/): Assign R or S to chiral centers using an interactive 3D model.
- [Assign E or Z Stereochemistry](https://realochem.study/stereochemistry-EZ/): Determine E/Z configuration of alkenes using Cahn-Ingold-Prelog priority rules.
- [Identify meso Compounds](https://realochem.study/stereochemistry-meso/): Identify meso compounds by finding internal planes of symmetry.
- [Stereoisomer Relationships](https://realochem.study/stereochemistry-relationships/): Classify pairs of molecules as enantiomers, diastereomers, or identical.
- [Isomer Relationships](https://realochem.study/isomer-relationships/): Two molecules, one formula: structural isomers, enantiomers, diastereomers, or identical?
- [Molecule Relationships](https://realochem.study/molecule-relationships/): Classify molecule pairs: different molecules, structural isomers, resonance forms, enantiomers, diastereomers, conformations, or identical.
- [Fischer Projections: Assign R/S](https://realochem.study/fischer-rs/): Assign R/S from Fischer projections, including the horizontal-bond reversal rule, sugars, and amino acids.
- [Fischer Projections: Compare & Convert](https://realochem.study/fischer-relationships/): Practice the legal moves: classify Fischer pairs, and match Fischer projections to line-angle drawings.
- [Fischer Projections: Meso or Chiral](https://realochem.study/fischer-meso/): Spot the internal mirror plane in a Fischer projection, or show the molecule is chiral.
- [Newman Projections: Identify](https://realochem.study/newman-projections/): Identify anti, gauche, and eclipsed conformations on sight.
- [Newman Projections: Build](https://realochem.study/newman-build/): Translate wedge-dash structures by placing substituents interactively.
- [Newman Projections: Rotate](https://realochem.study/newman-rotate/): Rotate Newman projections to match with line-angle drawings.
- [Chair Conformations: Ring Flip](https://realochem.study/chair-conformations/): Place substituents in the correct axial or equatorial positions on a flipped chair. Easy, Medium, and Hard difficulty modes.
- [Chair Conformations: Energy](https://realochem.study/chair-energy/): Compare chair conformers and pick the more stable one using A-values.
- [Which Boils Higher?](https://realochem.study/bp-ranking/): Two structures, measured boiling points: pick the higher, then name the deciding force.
- [Which Melts Higher?](https://realochem.study/mp-ranking/): Compare measured melting points, where crystal packing matters as much as attraction.
- [Boiling Point Trends](https://realochem.study/bp-trends/): Drag three structures into boiling-point order: each set varies exactly one feature — chain length, branching, halogen size, O–H count, or force class.
- [Boiling vs Melting Inversions](https://realochem.study/mpbp-inversions/): Pairs where the two properties disagree: one compound boils higher, the other melts higher.
- [Count ¹H NMR Signals](https://realochem.study/proton-nmr-signals/): Predict how many distinct signals a compound shows in its ¹H NMR spectrum, with color-coded equivalent-proton answer keys.
- [Count ¹³C NMR Signals](https://realochem.study/carbon-nmr-signals/): Predict the number of distinct ¹³C NMR signals, with color-coded equivalent-carbon answer keys.
- [Find Equivalent Protons](https://realochem.study/equivalent-protons/): Click every position that is chemically equivalent to a highlighted atom and learn homotopic, enantiotopic, and diastereotopic relationships.
- [Predict Splitting Patterns](https://realochem.study/splitting-patterns/): Apply the n+1 rule to predict multiplicity, from singlets to septets, with worked explanations.
- [Predict Complex Splitting (dd, dt)](https://realochem.study/complex-splitting/): Name compound multiplets where the J values genuinely differ, with splitting-tree answer keys.
- [Match the Molecule to the Integration](https://realochem.study/integration-matching/): Given a ¹H NMR integration ratio, pick which of three candidate structures fits its proton partition.
- [Assign ¹H NMR Spectra](https://realochem.study/proton-nmr-assignment/): Match every signal in a spectrum reconstructed from published experimental data to the protons that produce it, with zoomable multiplets.
- [Assign ¹³C NMR Spectra](https://realochem.study/carbon-nmr-assignment/): Match each line in a proton-decoupled ¹³C spectrum to its carbon; crowded regions are shown but honestly left unasked.
- [NMR Integration: Match the Spectrum](https://realochem.study/nmr-integration/): Three candidate structures all share the same ¹H NMR integration ratio — read the chemical shifts and splitting on the spectrum to pick the one that fits.
- [DEPT Practice: Classify Every Carbon](https://realochem.study/dept-practice/): Read ¹³C, DEPT-90, and DEPT-135 spectra together and classify each carbon as CH₃, CH₂, CH, or quaternary.
- [Nitrogen Rule](https://realochem.study/nitrogen-rule/): Read the nominal mass of M⁺• and call the strongest claim it supports about the nitrogen count.
- [Degrees of Unsaturation](https://realochem.study/degrees-of-unsaturation/): Turn a molecular formula into its ring + π-bond count, then find every degree on the revealed structure.
- [Isotope Patterns](https://realochem.study/isotope-patterns/): Read the M+2 cluster to identify Cl/Br content, or count carbons from the M+1 peak.
- [Exact Mass (HRMS)](https://realochem.study/exact-mass/): Real published HRMS values, two directions: identify the adduct from a known formula, or pin the formula down to millidaltons.
- [Assign the Band](https://realochem.study/ir-band-id/): One band highlighted on a real IR spectrum — name the stretch it belongs to.
- [Spot the Group](https://realochem.study/ir-functional-groups/): Structure hidden, spectrum shown: call the functional group the bands demand.
- [Predict the Bands](https://realochem.study/ir-predict-bands/): From the structure, call which bands the real spectrum shows — and which tempting bands stay silent.
- [Match the Structure](https://realochem.study/ir-structure-match/): One real spectrum, four structures: eliminate the three the band data rules out.
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## Literature reactions

Real reactions from the primary literature, one page per reaction family with a page per reaction type inside it: reactants, conditions, products and yield as drawn schemes, each with its citation. Printable worksheets are linked from every page.

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- [Aliphatic nucleophilic substitution](https://realochem.study/reactions/aliphatic-substitution/): 64 literature examples with citations, drawn as reaction schemes, covering Alcohol to alkyl halide, Leaving group displacement, N-alkylation, and 10 more types
- [Elimination](https://realochem.study/reactions/beta-elimination/): 36 literature examples with citations, drawn as reaction schemes, covering Elimination to alkyne, Leaving group elimination, Dehydration of alcohol, and 6 more types
- [Electrophilic aromatic substitution](https://realochem.study/reactions/eas/): 57 literature examples with citations, drawn as reaction schemes, covering EAS halogenation, EAS nitration, Friedel–Crafts acylation, and 6 more types
- [Nucleophilic aromatic substitution](https://realochem.study/reactions/nas/): 9 literature examples with citations, drawn as reaction schemes, covering SNAr
- [Diazonium chemistry](https://realochem.study/reactions/diazonium/): 13 literature examples with citations, drawn as reaction schemes, covering Sandmeyer, Deamination, Aryl azide formation, and 1 more type
- [Oxidation and reduction of aromatic compounds](https://realochem.study/reactions/aromatic-redox/): 25 literature examples with citations, drawn as reaction schemes, covering Benzylic oxidation, Benzylic halogenation, Nitro reduction, and 2 more types
- [Enols and enolate formation (fundamentals)](https://realochem.study/reactions/enols-and-enolates/): 21 literature examples with citations, drawn as reaction schemes, covering Keto–enol tautomerization, Silyl enol ether formation, Kinetic enolate formation, and 6 more types
- [Enolate alkylation](https://realochem.study/reactions/enolate-alkylations/): 11 literature examples with citations, drawn as reaction schemes, covering Enolate C-alkylation, Malonic ester synthesis
- [Alpha-halogenation](https://realochem.study/reactions/enolate-halogenation/): 25 literature examples with citations, drawn as reaction schemes, covering α-Halogenation (acidic), Hell–Volhard–Zelinsky, Haloform, and 2 more types
- [Aldol and related condensations](https://realochem.study/reactions/aldol/): 26 literature examples with citations, drawn as reaction schemes, covering Intramolecular aldol, Aldol condensation, Aldol addition, and 3 more types
- [Claisen condensations and enolate acylation](https://realochem.study/reactions/claisen-condensations/): 17 literature examples with citations, drawn as reaction schemes, covering Claisen condensation, Dieckmann, Enolate C-acylation
- [Conjugate addition, annulation, cascades](https://realochem.study/reactions/more-complex-enolate-reactions/): 22 literature examples with citations, drawn as reaction schemes, covering Robinson annulation, Michael addition, Decarboxylation, and 1 more type
- [Olefination](https://realochem.study/reactions/olefination/): 16 literature examples with citations, drawn as reaction schemes, covering Wittig, Horner–Wadsworth–Emmons
- [Diels–Alder and other cycloadditions](https://realochem.study/reactions/diels-alder/): 16 literature examples with citations, drawn as reaction schemes, covering Diels–Alder, Hetero-Diels–Alder, Retro-Diels–Alder, and 2 more types
- [Electrocyclic reactions](https://realochem.study/reactions/pericyclic-reactions/): 11 literature examples with citations, drawn as reaction schemes, covering 4π electrocyclization, 6π electrocyclization
- [Sigmatropic rearrangements](https://realochem.study/reactions/sigmatropic/): 5 literature examples with citations, drawn as reaction schemes, covering [1,5]-H sigmatropic shift, Claisen rearrangement, Other sigmatropic rearrangement
- [Radical reactions](https://realochem.study/reactions/radicals/): 18 literature examples with citations, drawn as reaction schemes, covering Benzylic halogenation, Allylic halogenation, Radical cyclization, and 2 more types
- [Nucleophilic addition to aldehydes and ketones](https://realochem.study/reactions/carbonyl-addition/): 60 literature examples with citations, drawn as reaction schemes, covering Grignard addition, Acetal formation, Hydrate formation, and 10 more types
- [Nucleophilic acyl substitution](https://realochem.study/reactions/acyl-substitution/): 71 literature examples with citations, drawn as reaction schemes, covering Amide formation, Acid chloride formation, Fischer esterification, and 11 more types
- [Addition to alkenes and alkynes](https://realochem.study/reactions/alkene-alkyne-addition/): 52 literature examples with citations, drawn as reaction schemes, covering Halogenation of alkene, Carbene cyclopropanation, HX addition, and 9 more types
- [Oxidations and reductions](https://realochem.study/reactions/oxidation-reduction/): 40 literature examples with citations, drawn as reaction schemes, covering Alcohol oxidation, Nitro reduction, Aldehyde oxidation, and 10 more types
- [Rearrangements](https://realochem.study/reactions/rearrangements/): 7 literature examples with citations, drawn as reaction schemes, covering Curtius rearrangement, Pinacol rearrangement, Beckmann, and 2 more types
- [Organometallic reagents and cross-coupling](https://realochem.study/reactions/organometallic-and-coupling/): 11 literature examples with citations, drawn as reaction schemes, covering Grignard formation, Acetylide formation, Grignard protonolysis, and 2 more types
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## General chemistry practice

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- [Subatomic Particles](https://realochem.study/subatomic-particles/): Find the number of protons, neutrons, and electrons for any element or ion.
- [Significant Figures](https://realochem.study/significant-figures/): Count sig figs and round answers correctly in calculation problems.
- [Dimensional Analysis](https://realochem.study/dimensional-analysis/): Convert between units using dimensional analysis with step-by-step practice.
- [Electron Configuration](https://realochem.study/electron-configuration/): Write electron configurations for atoms and ions using the Aufbau principle.
- [Lewis Structures](https://realochem.study/lewis-structures/): Draw Lewis dot structures for molecules and ions interactively.
- [Molecular Geometry (VSEPR)](https://realochem.study/molecular-geometry/): Predict molecular shapes and bond angles using VSEPR theory.
- [Atomic & Ionic Size](https://realochem.study/atomic-size/): Compare atomic and ionic radii across the periodic table.
- [Periodic Trends (IE, EN, EA)](https://realochem.study/periodic-trends/): Compare ionization energy, electronegativity, and electron affinity across elements.
- [Oxidation Numbers](https://realochem.study/oxidation-numbers/): Assign oxidation states to atoms in compounds and ions.
- [Balancing Equations](https://realochem.study/balancing-equations/): Balance chemical equations one coefficient at a time.
- [Le Chatelier's Principle](https://realochem.study/le-chatelier/): Predict how equilibrium shifts in response to changes in conditions.
- [Naming Compounds](https://realochem.study/naming-compounds/): Name ionic, covalent, and acid compounds from their formulas.
- [Polyatomic Ions](https://realochem.study/polyatomic-ions/): Memorize polyatomic ion names and formulas with flashcard-style practice.
- [Mole Conversions](https://realochem.study/mole-conversions/): Convert between moles, grams, and particles step by step.
- [Limiting Reagent](https://realochem.study/limiting-reagent/): Identify limiting reagents and calculate theoretical yields.
- [Dilution (M₁V₁=M₂V₂)](https://realochem.study/dilution/): Solve dilution problems using the M1V1=M2V2 equation.
- [Gas Laws](https://realochem.study/gas-laws/): Solve ideal gas law, combined gas law, and partial pressures problems.
- [Acid/Base Strength](https://realochem.study/acid-base-strength/): Compare acid and base strength using structure and periodic trends.
- [Thermochemistry](https://realochem.study/thermochemistry/): Solve enthalpy, Hess's law, and calorimetry problems.
- [Nuclear Chemistry](https://realochem.study/nuclear-chemistry/): Solve nuclear decay, half-life, and nuclear equation balancing problems.
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## Optional

- [About](https://realochem.study/about/): who builds RealOChem and how it works
- [License](https://realochem.study/license/): content is CC BY-NC 4.0
- [Credits](https://realochem.study/credits/): data sources and open-source attribution
- [Privacy](https://realochem.study/privacy/): privacy policy