---
title: "Two-Dimensional NMR and Assigning a Whole Structure"
description: "A two-dimensional experiment shows which signals are connected rather than only where they sit. Using two or three of them together, a structure can be assigned atom by atom instead of guessed and che"
canonical: https://lightmysky.com/learn/science/two-dimensional-nmr-and-assigning-a-whole-structure-mt_UEC4dilKT9
source: https://lightmysky.com/learn/science/two-dimensional-nmr-and-assigning-a-whole-structure-mt_UEC4dilKT9.md
retrieved: 2026-09-12
---

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# Two-Dimensional NMR and Assigning a Whole Structure

A two-dimensional experiment shows which signals are connected rather than only where they sit. Using two or three of them together, a structure can be assigned atom by atom instead of guessed and checked.

Subject: Science · Area: Chemistry · Ages 21 to 22
Page: https://lightmysky.com/learn/science/two-dimensional-nmr-and-assigning-a-whole-structure-mt_UEC4dilKT9

## Ready when they can

- Reads a COSY map to trace a chain of coupled protons
- Uses a one-bond correlation experiment to attach each proton to its own carbon
- Uses a long-range correlation experiment to join fragments across a quaternary carbon
- Assembles the evidence from several spectra into one assigned structure and states the weakest link in the argument

## Lesson: Maps of connected signals

You already know a one-dimensional spectrum shows where signals sit. A two-dimensional experiment shows which signals are connected. Each spot off the diagonal links two signals, so you read relations instead of guessing them.

**Example.** A COSY map traces chains of coupled protons. Start at one proton, follow its cross-spot to the neighbour, then to the next. Walking the spots walks the chain, proton by proton, through the fragment.

A one-bond map attaches each proton to its own carbon. Every spot pairs one proton with the carbon holding it, so each chain from the COSY walk gains its carbon skeleton. Now every proton knows its carbon.

**Tip.** A long-range map joins fragments across carbons with no protons, such as quaternary centres. Assemble all three maps into one structure, then name the weakest link: the correlation with the fewest supporting spots carries the least weight.

**Recap.** COSY walks the proton chains, the one-bond map adds carbons, and long-range spots bridge the silent centres.

## Practice

8 questions on this page, each with its working shown.

## Needs first

- [Diastereomers, Meso Compounds and Fischer Projections](https://lightmysky.com/learn/science/diastereomers-meso-compounds-and-fischer-projections-mt_1r5vCBK9zr)
- [Carbon-13, DEPT and Coupling Constants](https://lightmysky.com/learn/science/carbon-13-dept-and-coupling-constants-mt_9K6GkAkqq1)

## Opens up

- [Potentiometry, Ion-Selective Electrodes and Voltammetry](https://lightmysky.com/learn/science/potentiometry-ion-selective-electrodes-and-voltammetry-mt_7sLJXqFfWR)
- [Structure Elucidation from a Complete Data Set](https://lightmysky.com/learn/science/structure-elucidation-from-a-complete-data-set-mt_O2uungksMZ)
- [Characterisation Standards: What Counts as Proof of a New Compound](https://lightmysky.com/learn/science/characterisation-standards-what-counts-as-proof-of-a-new-compound-mt_WKhYUq-eyd)