Organic Chemistry NMR and IR Key Concepts for Students

Aromatic

7-8

Aldehyde

9-10

Carboxylic acid

10-12

Carbonyl (NMR)

160-220 δ (ppm)

OH (alcohol) IR signal

3300 broad

NH IR signal

3300 sharp

C≡N (nitrile) IR signal

2250

C≡C IR signal

2150

Carbonyl C=O IR signal

1700 strong

Ester IR signal

1735

Aldehyde IR signal

1720 and 2750-2850 (two bumps)

methyl H NMR

0.9

Methylene CH2 H NMR

1.2

Methine CH H NMR

1.7

When are protons shifted downfield?

Protons are shifted downfield when they're near electronegative atoms and are being deshielded.

Oxygen (of an alcohol or ether) shift

+2.5

Oxygen (of an ester) shift

+3

Carbonyl group (all carbonyl groups, like ketones, aldehydes, and esters)

+1

methyl (connected to one R group) C NMR

10-30

Methylene (connected to two R groups) C NMR

15-55

Methyl (connected to three or four R groups) C NMR

20-60

C-I C NMR

0-40

C-Br C NMR

25-65

C-N C NMR

40-60

C-Cl C NMR

35-80

C-O C NMR

40-80

C tripled bond C NMR

65-90

C=C C NMR

100-150

Aromatic C NMR

110-170

Carbonyl group of carboxylic acid, ester, or amide C NMR

165-185

Carbonyl group of an aldehyde or ketone C NMR

185-220