How can I draw NMR splitting diagrams?

1 Answer
Write your answer here...
Start with a one sentence answer
Then teach the underlying concepts
Don't copy without citing sources
preview
?

Answer

Write a one sentence answer...

Answer:

Explanation

Explain in detail...

Explanation:

I want someone to double check my answer

Describe your changes (optional) 200

9
Dec 17, 2014

The general rule for #""^1"H"# NMR spectra is: n neighbouring protons with the same coupling constant J will split a signal into n+1 lines.

We draw a "splitting tree" for each proton or group of protons.

img.docstoccdn.com

No Adjacent Protons

No splitting. Draw a single line.

1 Adjacent Proton

Draw 2 lines (a doublet) separated by #J_(ax)#.

2 Adjacent Protons

From each line of the doublet, draw two more lines separated by #J_(ax)#. Stack the overlapping lines. This gives a triplet with area ratios 1:2:1.

3 Adjacent Protons

From each line of the triplet, draw two more lines separated by #J_(ax)#. Stack the overlapping lines. This gives a quartet with area ratios 1:3:3:1.

Repeat the process as many times as needed.

The relative intensity ratios are given by Pascal's triangle.

orgchem.colorado.edu

Here are some splitting patterns that you should be able to draw quickly.

AX doublet-doublet: -CH-CH-

AX₂ doublet-triplet: -CH-CH₂-

nationalvetcontent.edu.au

AX₃ doublet-quartet: CH₃CH-

www2.chemistry.msu.edu

AX₆ doublet-septet: (CH₃)₂CH- (an isopropyl group!)

www.chem.ucla.edu

Note: A septet often looks like a quintet with the wrong intensities, because the two outermost lines are so weak.

A₂X₃ triplet quartet: CH₃CH₂- (an ethyl group!)

www.brynmawr.edu

Here's a video that gives an introduction to NMR splitting patterns.

Was this helpful? Let the contributor know!
1500
Trending questions
Impact of this question
7933 views around the world
You can reuse this answer
Creative Commons License