Organic Pulse
Free organic chemistry · B.Sc. to NET
Watch electrons move, turn molecules in 3D, read the essentials and learn to write answers that score. Free, in English, for every chemistry student.
Four leads of learning
Built on the four-quadrant approach of India's MOOC guidelines, so each topic is complete: watch it, read it, explore it, test it.
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Each one has all four quadrants: the short, full notes with a PDF, ten checked references and exam practice.
Hold the molecule
Turn (R)-2-bromobutane with your finger. Then let the molecule show you how to assign its configuration, step by step.
Higher atomic number wins: Br (35) beats C (6) beats H (1). For the two carbons, compare the next atoms: C₂H₅ has (C, H, H), CH₃ has (H, H, H), so ethyl wins.
Lesson preview
Chapter: Nucleophilic substitution · about 30 minutes
Answer-Writing Studio
Start the timer, write on your own paper, then open the marking scheme and score yourself honestly, point by point.
Q. Explain the SN2 mechanism of (R)-2-bromobutane with aqueous NaOH. Why is the product optically active?
Write your answer on paper before you look at the scheme.
Marking scheme
Finished writing? Open the scheme and tick each point you wrote.
OH⁻ attacks C2 from the side opposite to Br (back-side attack, 180°). In the single transition state, C2 is partly bonded to both OH and Br, with H, CH₃ and C₂H₅ in one plane. Br⁻ leaves and the three groups flip like an umbrella (Walden inversion), giving (S)-butan-2-ol. Only one enantiomer forms, so the product is optically active.
Draw the arrows: lone pair → C, C–Br bond → Br.
Meet your teacher
Associate Professor & Head, Department of Chemistry
Lonavala Education Trust's Dr. B.N. Purandare Arts, Smt. S.G. Gupta Commerce & Smt. Shardaben Amrutlal Mithaiwala Science College, Valvan, Lonavala (affiliated to Savitribai Phule Pune University)
Organic Pulse began with one belief: every reaction has a pulse. Students understand chemistry best when they can see electrons move and test themselves straight away.
Organic Pulse is a personal educational initiative. Views and content are the author's own and do not represent the official views of the institution.
On YouTube
New Organic Pulse shorts every day: mechanisms, mistakes to spot and exam traps.
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