C13 NUCLEAR MAGNETIC RESONANCE

(NMR)

13C NMR

C13 resonances occur from 0 to 200 ppm (δ).

These peaks are split by the attached hydrogens.

However, proton decoupled (broadband) spectra are not split by H.

13C NMR

Distortionless enhancement by polarization transfer (DEPT) spectra permit identification of CH3, CH2, and CH carbon atoms.

DEPT 45 shows 1o, 2o,and 3o carbons.DEPT 90 shows only 3o carbons.DEPT 135 shows 1o and 3o carbons as positive peaks and 2o carbons as negative peaks.

13C NMR C environment δ, ppm C environment δ, ppmSaturated carbons 0-55 Acetylenic -C C- 60-90

primary R-CH3 4-30secondary R2-CH2 12-50 Benzenoid 120-140tertiary R3-CH 22-54quaternary R4-C 29-47 Carbonyl C=O 150-220

amides & imides 150-180Olefinic carbons 100-165 esters & anhydrides155-185

R2C=CH2 100-110 acids 170-190R-CH=CH2 110-120 ketones 185-220R-CH=CH-R 125-150 aldehydes190-210CH2=CH-R 130-154CH2=CR2 140-165 Nitriles R-C N 115-125

Alenes Azomethine R2C=N-R 145-165C=C=C 70-95C=C=C 200-215

13C Off-resonance decoupled spectrum

13C Off-resonance & Broadband decoupled spectra

Broadband

Off-resonance

13C Broadband decoupled spectrum

13C NMR – n-Hexane

Broadband

13C NMR – Acetone

Broadband

Broadband

1H & 13C NMR: 1,1,2-trichloropropane

1H & 13C NMR: 2-methyl-2-butene

Broadband

1H & 13C NMR: 2-methyl-1-butene

Broadband

13C NMR – 6-methyl-5-hepten-2-ol

BroadbandAll carbons as singlets

13C NMR – 6-methyl-5-hepten-2-ol

DEPT 90Only CH carbons

13C NMR – 6-methyl-5-hepten-2-ol

DEPT 135Methyl and CH positiveMethylene negative

ENDC13 NMR