13C DEPT and APT

Experiment:

C13CDEPT45

Discussion:
EtBzcarThis DEPT experiment (Distortionless Enhancement by Polarization Transfer) is an example of a carbon-editing pulse sequence. Systematic changes in the internal delays in the complex pulse program make different carbons respond in different fashions, based upon the number of protons attached.

The DEPT 45 experiment yields a positive peak for every carbon with attached protons: Ca at 16 ppm, Cb at 29 ppm, and Cd, Ce, and Cf at 128.5, 128.9, and 129 ppm, respectively. Note in the spectrum below that carbon in the CDCl3 solvent does not give a signal, since it has no attached protons.
Spectrum of Ethyl Benzene:

(Click on the spectrum to obtain a magnified view.)

dept45

Experiment:

C13CDEPT90

Discussion:
EtBzcarIn this variant of the DEPT experiment, only CH yields peaks; CH0, CH2, and CH3 are invisible.  In our example we see only three lines due to Cd, Ce, and Cf in the aromatic range from 126 to 129 ppm.

Spectrum of Ethyl Benzene:

(Click on the spectrum to obtain a magnified view.)

dept90

 

Experiment:

C13CDEPT135

Discussion:
EtBzcarIn this variant of the DEPT experiment, CH2 yields negative peaks, whereas CH and CH3 are positive.  Thus, we see Ca, Cd, Ce, and Cfas positive peaks, while Cb is negative.

Spectrum of Ethyl Benzene:

(Click on the spectrum to obtain a magnified view.)

dept135

 

Experiment:

apt

Discussion:
EtBzcarWhereas the APT (Attached Proton Test) experiment is not as sensitive as a DEPT experiment, the APT has the advantage of seeing all carbons present: CH0 at 145 ppm and CH2 at 29 ppm are negative, while CH3 at 16 ppm and CH in the range of 126-129 ppm are positive. Thus Cc and Cb are negative, while Ca, Cd, Ce, and Cf are positive.

Spectrum of Ethyl Benzene:

(Click on the spectrum to obtain a magnified view.)

apt