Guide · OrgoMech: O-Chem Predictor
SN1 vs SN2 explained: how to predict which substitution wins
Organic chemistry finals and MCAT-style items still test SN1 versus SN2 because the two paths look similar on paper and behave differently in the flask. The winning answer is a prediction: substrate, nucleophile, leaving group, solvent — then the arrows.
Published 2026-09-19 · 10 min read
The one-line difference
SN2 is concerted: nucleophile attacks as the leaving group leaves, inversion of configuration, rate depends on both substrate and nucleophile. SN1 is stepwise: the leaving group leaves first, a carbocation forms, then the nucleophile attacks — often racemization, rate depends mainly on the substrate.
Decision factors that get tested
- Substrate: methyl and primary favor SN2; tertiary favors SN1; secondary is the exam trap.
- Nucleophile: strong, compact nucleophiles push SN2; weak nucleophiles (often the solvent) fit SN1.
- Leaving group: both need a decent leaving group; a terrible one kills both paths.
- Solvent: polar protic often helps SN1; polar aprotic often helps SN2.
How OrgoMech helps you stop guessing
OrgoMech is an iOS o-chem predictor: build a reactant, choose reagents, and see major and minor products plus the curved-arrow mechanism step by step. The reaction library covers SN1/SN2, E1/E2, additions, carbonyls, aromatics, and redox — with a study plan that counts down to your final. It is a study aid, not a homework answer key.
Frequently asked questions
Is OrgoMech a homework answer key?
No. It is a study tool to predict products and learn mechanisms. Use it to understand reactions — not to skip the work your course requires.
Does it cover SN1, SN2, E1, and E2?
Yes — plus additions, carbonyls, aromatics, and redox in the reaction library, each with reagents, conditions, products, and mechanisms.
OrgoMech is an educational study aid, not a substitute for your course, textbook, lab, or instructor.
OrgoMech: O-Chem Predictor
Organic chemistry does not have to wreck your GPA.
OrgoMech turns confusing reactions into clear, visual answers. Build a reactant, choose your reagents, and instantly see the major and minor products — plus the full electron-pushing mechanism, arrow by arrow.