The deuterated solvent e.g. CDCl3 when used in NMR spectroscopy shows signal , is it because of the residual proton or there are some other factors?
a) impurity, but for some solvents extra-pure (for deuterium) versions are also available;
b) a water-miscible and exchangeable deuterium (proton) containing solvents adsorb H2O from the air (or sample contains water), and deuterium substituted with a proton (D2O, d3-MeOD, d6-DMSO, etc.), this also occurs when the sample contains exchangeable proton(s).
In case b), the improperly closed bottle helps to increase the amount of " normal" solvent. The same is to the solvent from a refrigerator used before it reaches room temperature.
In the case of water-immiscible and lack of exchangeable proton-containing solvents water signal appears, which can change its location upon the water content. Please remember that in CDCl3, deuterium can slowly exchange with proton, and the water (impurity/adsorbed) or exchangeable protons results in CHCl3.
It is mostly the residual protons that you see. The solvent is typically deuterated to 99 - 99.9 % the rest is 1H. In Chloroform the residual signal is a signlet. In other solvents such as DMSO or Aceton it will shown up as 5 lines due to the coupling of one 1H in CD2H with the two deuterons.
yes, it is the residual proton and the proton exchanged from the moisture absorbed by the solvent. When the container is frequently exposed to the atmosphere, the intensity of CHCL3 peak considerably increases in the spectrum
Dear Tanvir Rahman . Deuteration is not "100%", so signals for the residual protons are observed. See the useful link: https://webspectra.chem.ucla.edu/NotesOnSolvents.html
- Badges
- Science topic
- Similar topics
- Biological Science
- Biochemistry
- Enzymology
- Enzymes