NMR spectra are usually recorded with the sample dissolved in a solvent. For 1H NMR this creates a problem: most organic solvents contain hydrogen atoms, and there is far more solvent than sample. The solvent would give huge peaks that swamp the peaks of the compound being analysed.The solution is to use a solvent that contains no 1H atoms. Two suitable solvents are:
• Deuterated solvents, such as CDCl3. In a deuterated solvent the 1H atoms have been replaced by deuterium, D or 2H, an isotope of hydrogen with one proton and one neutron.
• Tetrachloromethane, CCl4, which contains no hydrogen at all.Deuterium nuclei absorb at a very different frequency from 1H nuclei, so a deuterated solvent gives no peak in a 1H NMR spectrum. The only peaks seen come from the sample and the TMS standard at 0 ppm.CDCl3 is chemically almost identical to CHCl3, so it dissolves the same wide range of organic compounds. It is also fairly unreactive, so it does not react with the sample.Example: if a sample of ethanol were dissolved in ordinary CHCl3, the spectrum would show a very large extra peak from the H in CHCl3. Dissolving it in CDCl3 instead removes that peak, leaving only the three ethanol peaks.Remember the purpose: deuterated solvents are used so that the solvent does not produce a signal in the 1H NMR spectrum.
• Deuterated solvents, such as CDCl3. In a deuterated solvent the 1H atoms have been replaced by deuterium, D or 2H, an isotope of hydrogen with one proton and one neutron.
• Tetrachloromethane, CCl4, which contains no hydrogen at all.Deuterium nuclei absorb at a very different frequency from 1H nuclei, so a deuterated solvent gives no peak in a 1H NMR spectrum. The only peaks seen come from the sample and the TMS standard at 0 ppm.CDCl3 is chemically almost identical to CHCl3, so it dissolves the same wide range of organic compounds. It is also fairly unreactive, so it does not react with the sample.Example: if a sample of ethanol were dissolved in ordinary CHCl3, the spectrum would show a very large extra peak from the H in CHCl3. Dissolving it in CDCl3 instead removes that peak, leaving only the three ethanol peaks.Remember the purpose: deuterated solvents are used so that the solvent does not produce a signal in the 1H NMR spectrum.