---
title: "Carbon-13, DEPT and Coupling Constants"
description: "The carbon spectrum shows the skeleton directly, and an editing experiment says how many hydrogens sit on each carbon. Coupling constants, read carefully, then report on geometry rather than just on n"
canonical: https://lightmysky.com/learn/science/carbon-13-dept-and-coupling-constants-mt_9K6GkAkqq1
source: https://lightmysky.com/learn/science/carbon-13-dept-and-coupling-constants-mt_9K6GkAkqq1.md
retrieved: 2026-09-12
---

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# Carbon-13, DEPT and Coupling Constants

The carbon spectrum shows the skeleton directly, and an editing experiment says how many hydrogens sit on each carbon. Coupling constants, read carefully, then report on geometry rather than just on neighbours.

Subject: Science · Area: Chemistry · Ages 20 to 21
Page: https://lightmysky.com/learn/science/carbon-13-dept-and-coupling-constants-mt_9K6GkAkqq1

## Ready when they can

- Explains why a routine carbon spectrum shows singlets and why the integrals are not reliable
- Reads a DEPT experiment to classify each carbon by the number of attached protons
- Extracts a coupling constant in hertz and uses its size to argue for cis or trans geometry
- Combines carbon and proton evidence to distinguish two candidate structures

## Lesson: Reading carbon spectra and couplings

The carbon spectrum shows the skeleton directly, one signal per distinct carbon. Routine spectra show singlets because proton splitting is removed. Peak heights cannot be trusted for counting, so integrals are unreliable.

An editing experiment called DEPT sorts carbons by attached protons. It tells CH3, CH2, and CH apart. Carbons with no protons stay silent, which is itself a clue.

**Example.** A coupling constant in hertz reports on geometry, not just neighbours. Given cis and trans candidates, the larger coupling fits the trans one and the smaller fits cis. Size argues the geometry.

**Tip.** Combine both nuclei to kill one candidate. If a carbon signal or a coupling fits only one structure, the other is out. Name the exact signal that decided it.

**Recap.** Carbon maps the skeleton, DEPT counts attached protons, and coupling size argues geometry.

## Practice

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

## Needs first

- [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)

## Opens up

- [Two-Dimensional NMR and Assigning a Whole Structure](https://lightmysky.com/learn/science/two-dimensional-nmr-and-assigning-a-whole-structure-mt_UEC4dilKT9)