# 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; institutional licensing is available — 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

- [R and S configuration](https://realochem.study/stereochemistry-RS/): assign R/S at stereocenters with CIP priority rules and detailed answer keys
- [E and Z configuration](https://realochem.study/stereochemistry-EZ/): assign E/Z on alkenes using CIP priority rules
- [Meso compounds](https://realochem.study/stereochemistry-meso/): identify meso compounds and internal mirror planes
- [Stereoisomer relationships](https://realochem.study/stereochemistry-relationships/): enantiomers, diastereomers, or identical
- [Isomer relationships](https://realochem.study/isomer-relationships/): classify pairs sharing a molecular formula
- [Molecule relationships](https://realochem.study/molecule-relationships/): identical, isomers, resonance forms, or conformers
- [IUPAC nomenclature](https://realochem.study/IUPAC-nomenclature/): name organic molecules, with hints and answer keys
- [Guided nomenclature](https://realochem.study/guided-nomenclature/): step-by-step IUPAC naming on the structure itself
- [Nomenclingo](https://realochem.study/nomenclingo/): drag-and-drop name-building game from fragment tiles
- [Functional groups](https://realochem.study/functional-groups/): identify every functional group in a structure
- [Functional group detail](https://realochem.study/functional-group-detail/): precise labels — primary/secondary/tertiary, vinyl, allyl, benzyl, aryl
- [Count 1H NMR signals](https://realochem.study/proton-nmr-signals/): how many distinct proton signals, with color-coded equivalence answer keys
- [Count 13C NMR signals](https://realochem.study/carbon-nmr-signals/): how many distinct carbon signals, including diastereotopic carbons explained
- [Equivalent protons](https://realochem.study/equivalent-protons/): click every position sharing an NMR environment — homotopic, enantiotopic, diastereotopic
- [Splitting patterns](https://realochem.study/splitting-patterns/): n+1 rule multiplicity practice, singlet through septet
- [Line-angle structures](https://realochem.study/line-angle-reading/): convert skeletal structures to molecular formulas
- [Aromaticity](https://realochem.study/aromatic/): aromatic, antiaromatic, or nonaromatic by Hückel's rule
- [Resonance: formal charges](https://realochem.study/resonance-charges/): assign charges on resonance structures
- [Resonance: curved arrows](https://realochem.study/resonance-draw/): draw electron movement between resonance forms
- [Resonance: ranking](https://realochem.study/resonance-ranking/): pick the more significant contributor
- [Mechanism arrows](https://realochem.study/mechanism-draw/): draw curved-arrow mechanisms step by step
- [SN1/SN2/E1/E2](https://realochem.study/sn1-sn2-e1-e2/): predict substitution vs elimination from substrate, nucleophile, and solvent
- [Newman projections](https://realochem.study/newman-projections/): classify anti, gauche, and eclipsed conformations
- [Newman build](https://realochem.study/newman-build/): build Newman projections from wedge-dash structures
- [Newman rotate](https://realochem.study/newman-rotate/): rotate Newman projections to match wedge-dash structures
- [Chair conformations](https://realochem.study/chair-conformations/): ring flips — place substituents axial or equatorial
- [Chair energy](https://realochem.study/chair-energy/): rank chair stability with A-values
- [pKa pairs (DMSO)](https://realochem.study/pKa-pairs/): pick the more acidic compound, DMSO data from Reich and Bordwell
- [pKa pairs (water)](https://realochem.study/water-pka-pairs/): pick the more acidic compound, aqueous data from Evans and Ripin
- [Most acidic proton](https://realochem.study/acidic-proton/): click the most acidic atom in each molecule
- [Dipole moments](https://realochem.study/dipole-moment/): draw the net molecular dipole arrow

## General chemistry practice

- [Subatomic particles](https://realochem.study/subatomic-particles/): protons, neutrons, and electrons from isotope notation
- [Significant figures](https://realochem.study/significant-figures/): counting and rounding rules
- [Dimensional analysis](https://realochem.study/dimensional-analysis/): build unit-conversion chains from factor tiles
- [Electron configuration](https://realochem.study/electron-configuration/): full and noble-gas core notation for elements and ions
- [Lewis structures](https://realochem.study/lewis-structures/): drag-and-drop electrons into bonds and lone pairs
- [Molecular geometry](https://realochem.study/molecular-geometry/): VSEPR shapes from 2D and 3D structures
- [Periodic trends](https://realochem.study/periodic-trends/): ionization energy, electronegativity, electron affinity
- [Atomic size](https://realochem.study/atomic-size/): compare atomic and ionic radii
- [Naming compounds](https://realochem.study/naming-compounds/): ionic and covalent names and formulas
- [Polyatomic ions](https://realochem.study/polyatomic-ions/): names and formulas drill
- [Oxidation numbers](https://realochem.study/oxidation-numbers/): assign oxidation states in compounds and ions
- [Balancing equations](https://realochem.study/balancing-equations/): coefficients for all major reaction types
- [Limiting reagent](https://realochem.study/limiting-reagent/): determine which reactant runs out first
- [Mole conversions](https://realochem.study/mole-conversions/): grams, moles, and molar mass
- [Gas laws](https://realochem.study/gas-laws/): PV=nRT, combined, Boyle's, Charles's, Avogadro's
- [Dilution](https://realochem.study/dilution/): M1V1 = M2V2 calculations
- [Thermochemistry](https://realochem.study/thermochemistry/): q = mcΔT and heat of reaction
- [Nuclear chemistry](https://realochem.study/nuclear-chemistry/): decay types, half-life, nuclear equations
- [Le Chatelier's principle](https://realochem.study/le-chatelier/): predict equilibrium shifts
- [Acid-base strength](https://realochem.study/acid-base-strength/): strong vs weak acids and bases, conjugate pairs, Ka

## 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; commercial and institutional licensing available
- [Credits](https://realochem.study/credits/): data sources and open-source attribution
- [Privacy](https://realochem.study/privacy/): privacy policy