NMR at HMC
HMC Chemistry Department
13C DEPT and APT
13C DEPT and APT
[DEPT 45] | [DEPT 90] | [DEPT 135] | [APT]
Experiment:
HMC13CDEPT45
Discussion:
This 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:
Experiment:
HMC13CDEPT90
Discussion:
In 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:
Experiment:
HMC13CDEPT135
Discussion:
In this variant of the DEPT experiment, CH2
yields negative peaks, whereas CH and CH3 are
positive. Thus, we see Ca,
Cd, Ce, and Cf as positive
peaks, while Cb is negative.
Spectrum of Ethyl Benzene:
Experiment:
HMCapt
Discussion:
Whereas 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:
