What's the only letter
not on the periodic table?
Pick your answer — no Googling.
No credit card · 60-minute session · Real chemistry, real results
A real SN2 reaction,
broken down step-by-step.
This is how every Catalyst session works — we don't hand you answers. We build the thinking that generates them.
Identify the Nucleophile
Every reaction starts with electron density. We locate the nucleophile — the electron-rich species hunting for a positive charge.
Nu: → electrophileLone pairs, π bonds, and negative charges are your flags.
Map the Electron Flow
Curved arrows show exactly where electrons move. Two electrons per arrow — never guess, always track.
C–Br → C + Br⁻The leaving group departs as the nucleophile attacks. Simultaneous.
Predict the Product
Once you know where electrons land, the product draws itself. Inversion of stereochemistry at an sp³ carbon — Walden inversion.
R-X + Nu⁻ → R-Nu + X⁻SN2: backside attack, one step, second-order kinetics.
Check Stability & Confirm
Resonance, induction, and hyperconjugation all influence product stability. We verify and build intuition for the next mechanism.
ΔG = ΔH – TΔSThermodynamics tells you if it happens. Kinetics tells you how fast.
Every concept taught this way — systematic, visual, unforgettable.
See this method in your free sessionTutors who've been
exactly where you are.
Each tutor pairs deep expertise with a personal molecule — the one that made their own chemistry click.
Dr. Priya Nair
PhD Organic Chemistry, MIT · Former GSI
“I failed my first orgo exam. I know exactly where the confusion lives.”
"Caffeine is a methylxanthine — it's the perfect molecule to teach about nitrogen lone pairs, aromaticity, and hydrogen bonding all at once."
Marcus Webb
MS Biochemistry, Johns Hopkins · MCAT 524
“The MCAT doesn't test memorization. It tests whether you can think like a biochemist.”
"ATP is the universal energy currency. Once students truly understand phosphoanhydride bonds, cellular respiration becomes a story, not a list."
Sofia Delgado
BS Chemistry, Caltech · AP Chem Score: 5
“A C+ doesn't mean you're bad at chemistry. It means nobody explained it right yet.”
"Water seems simple until you explain why ice floats, why it has such a high boiling point, and why life exists. Simple molecules teach the deepest principles."
60 minutes.
One concept, fully owned.
Every session follows this rhythm. Each phase is designed so that by the end, you're not hoping you understand — you know.
Diagnostic
15 minWe map exactly where understanding breaks down — not just which topics, but which specific misconceptions are blocking progress.
Concept Map
20 minWe build a visual map connecting the broken concept to everything you already understand. Chemistry is a network — we find your entry point.
Practice
20 minNot homework problems — deliberate practice targeting your exact gap. Each question is chosen to stress-test the new understanding.
Mastery Check
5 minYou explain the concept back — in your own words, to us. If you can teach it, you own it. This is the dopamine hit.
“I went from failing three straight exams to a 91 on my orgo final. The mastery check at the end of every session is what did it — I actually knew I knew it.”