---
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: 2026-11-12
---

> **Agent view.** This is the Markdown twin of the page, for tools and assistants.
> When to use this site, and the call that answers each job: https://lightmysky.com/agent-instructions.md
> API description (OpenAPI 3.1): https://lightmysky.com/openapi.json · Authentication: https://lightmysky.com/auth.md
> Pricing: https://lightmysky.com/pricing.md · Catalog: https://lightmysky.com/llms.txt · Full catalog: https://lightmysky.com/llms-full.txt
> Every machine-readable file on this domain: https://lightmysky.com/.well-known/ai-catalog.json
> Ask for Markdown with `Accept: text/markdown`, a `.md` address, or `?mode=agent`.

# 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.

A long-range map joins fragments across carbons with no protons, such as quaternary centres. Its spots link a proton to carbons two or three bonds away, so they can reach past a carbon that has no proton of its own. Assemble all three maps into one structure, then name the weakest link: the connection that rests on the fewest supporting spots.

**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

- [Carbon-13, DEPT and Coupling Constants](https://lightmysky.com/learn/science/carbon-13-dept-and-coupling-constants-mt_9K6GkAkqq1)

## Optional connections

- [Diastereomers, Meso Compounds and Fischer Projections](https://lightmysky.com/learn/science/diastereomers-meso-compounds-and-fischer-projections-mt_1r5vCBK9zr)

## 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)