NMR, HNMR, CNMR

NMR, HNMR, CNMR have many similarities

“Downfield” is where the electronegative atoms pull away the electrons from hydrogen nucleus. Because the electron of hydrogen is pulled away from the hydrogen nucleus, the NMR machine has a signal we see on the graph. The more downfield they go, the more “deshielded” protons (hydrogen) are.

Integration is where the arrow was pointed at ( in lab, the ruler was used to calculated this distance and ratio was determined – ratio can tell us how many hydrogen was attached to the unknown compound )

Problem solving technique… a quick guide for partial credits.

If your exam are based on the partial credit, please write as follow.

Step1

If the graph has 2 signals on 13CNMR, there are 2 “kinds” of carbons.

If the graph has 2 signals on 1HNMR, there are 2 “kinds” of protons. 

Step2

On the top of every splitting on 1HNMR

If there are 3 splitting, write “neighbor’s proton’s =2”

If there are 5 splitting, write “neighbor’s proton’s =4”

For every splitting, you minus one will give you the proton’s number.

Step3

For 1HNRM

If the ratio of the integration was given on the graph, for example 3:9.  This means 3 equivalent protons and 9 equivalent protons on that particular peak.

Step 4

Mark the downfield at the left side of the graph and defined its meaning

Downfield – the protons at the downfield is attached to the more electronegative atoms-for it’s electron was deshielded.

If you see IR spectrum C=O and OH band, then look for downfield singlet around 9-12 chemical shift. If there is one singlet, this position indicated the carboxylic acid proton. If you see the benzene region on IR spectrum on the right side, the look for 7 on HNMR, this is benzoic hydrogen.

Step 5

Determine the structure of the compounds…. This is based on the information was given on the graph. Most of time, you will have IR spectrum and Mass spectrum. If it is a multiple choice, try to come back and redo it because it takes more brain time.

Some facts keep in mind.

F>Cl>Br>I

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