What is the use of CDCL3 in NMR spectroscopy?
Andrew is correct that the FID from CHCl3 will swamp the cmpd signals, but there are other reasons for using CDCl3. (Otherwise why not use CCl4 or CS2?) On modern NMR machines you need a “deuterium lock” to hold the electronics steady whilst taking a spectrum (the field should be invariant). In other words you must have a significant quantity of a deuterated solvent present. In the old days chemists made CDCl3 for their NMR exps because it was easy to make. Even today it is the cheapest deuterated organic solvent available (as it is benzene-d6, acetone-d6 and DCM-d2 have more deuterium atoms). Because chemical shifts are solvent dependent chemists will record spectra in CDCl3 to be consistent with the older literature. CDCl3 always contains traces of CHCl3 and the NMR machine references the cmpd signals to the H-1 or C-13 resonance of residual CHCl3 and converts the shifts to TMS = 0.
