Deep-Dive Guides · Natural Products

Natural Products — the complete deep dive

This topic is less about memorising molecules and more about a method: how do you go from a plant/microbe to a pure compound, and from a pure compound to a proven structure? The organising idea is a funnel — molecular formula & degrees of unsaturation narrow the field; functional-group tests and spectroscopy (MS, IR, N.

Free extract — the opening section of the guide, in full.

0. How to use this guide — the elucidation funnel

Structure elucidation is a constraint-satisfaction funnel: each experiment removes possibilities until one structure survives. Never start by guessing the molecule — start by counting.

The elucidation funnel (order of operations): (1) Purity & molecular formula — HRMS gives the formula; compute degrees of unsaturation (DBE). (2) Functional groups — IR + qualitative tests + specific NMR shifts. (3) Carbon/proton framework — ¹³C count, ¹H integration, multiplicities. (4) Connectivity — 2D NMR (COSY, HSQC, HMBC) or classical degradation. (5) Stereochemistry — coupling constants, NOESY, optical methods, X-ray. Each step is a filter; the DBE number and the molecular formula are the two constraints you keep returning to.

Degrees of unsaturation (DBE / index of hydrogen deficiency): for CcHhNnOoXx, DBE = (2c + 2 + n − h − x)/2 (oxygen and divalent atoms don't count). Each ring OR π-bond = 1 DBE; a benzene ring = 4 (3 π + 1 ring); a C≡C or C≡N = 2. This single number, computed the instant you have the formula, often collapses the problem — e.g. DBE = 4 in a C₆ compound screams "benzene ring".

Read the rest of this guide

The remaining 11 sections — What are natural products? Biosynthetic classes, Isolation & purification, Structure elucidation — the strategy, The spectroscopic toolbox and more — are part of ChemVidya Full Access, along with the other guides, the books, the study notes and 6,000+ practice questions with worked solutions.

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