---
title: "NMR Spectra: Counting Environments"
description: "Carbon-13 and proton NMR report how many different environments a molecule has and, for protons, how many hydrogens sit in each. Splitting patterns then say how many hydrogens are on the neighbouring "
canonical: https://lightmysky.com/learn/science/nmr-spectra-counting-environments-mt_JquoiaxOMu
source: https://lightmysky.com/learn/science/nmr-spectra-counting-environments-mt_JquoiaxOMu.md
retrieved: 2026-09-12
---

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# NMR Spectra: Counting Environments

Carbon-13 and proton NMR report how many different environments a molecule has and, for protons, how many hydrogens sit in each. Splitting patterns then say how many hydrogens are on the neighbouring carbon.

Subject: Science · Area: Chemistry · Ages 17 to 18
Page: https://lightmysky.com/learn/science/nmr-spectra-counting-environments-mt_JquoiaxOMu

## Ready when they can

- Counts the carbon environments in a structure and matches the count to a carbon-13 spectrum
- Uses integration to get the ratio of hydrogens in each proton environment
- Applies the n plus one rule to predict or to read a splitting pattern
- Explains why TMS is used as the reference and why the solvent is deuterated

## Lesson: Counting neighbours in NMR

In NMR, each set of equivalent nuclei gives one signal. You count carbon 13 signals to count different carbon environments, and you count proton signals to count different hydrogen environments.

**Example.** Picture a spectrum with a triplet and a quartet in the ratio 3 to 2. You read it as an ethyl fragment, CH3 CH2. The 3H triplet is the CH3 split by its 2 neighbours, and the 2H quartet is the CH2 split by its 3 neighbours.

You use two tools together. Integration gives the ratio of hydrogens in each environment, and the n plus one rule turns neighbours into lines: hydrogens with n neighbours on the next carbon split into n plus one lines. Two neighbours give a triplet, three give a quartet.

**Tip.** You anchor every spectrum to TMS, an inert reference with one sharp peak defined as zero. You also run the sample in a deuterated solvent so the solvent brings no proton signal to swamp yours. A common slip is counting lines instead of environments.

**Recap.** Signal count gives environments, integration gives ratios, and neighbours set the splitting.

## Practice

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

## Needs first

- [The Electromagnetic Spectrum: Uses and Dangers](https://lightmysky.com/learn/science/the-electromagnetic-spectrum-uses-and-dangers-mt_P_NXNSo1zQ)
- [Mass Spectra and Infrared: Identifying an Unknown](https://lightmysky.com/learn/science/mass-spectra-and-infrared-identifying-an-unknown-mt_yotOEg9OTn)

## Opens up

- [Reading a Proton NMR Spectrum: Shift, Integration and Multiplicity](https://lightmysky.com/learn/science/reading-a-proton-nmr-spectrum-shift-integration-and-multiplicity-mt_WgxqHHf-YL)