Why there are differences in these spectra ? Which one is more useful and accurate ? What is the significance of using these two different methods ? enter image description here

  • $\begingroup$ Both are useful as for with one of the spectra and some usual extra work you can identify the molecule, for instance. In the couple of spectra you show, the main difference is seen in the O-H str region. Differences are due to hydrogen bonds in neat and the lack of in CCl4. The "hole" at low wavenumber is due to the latter ( abs). . $\endgroup$ – Alchimista Aug 9 '17 at 22:48
  • $\begingroup$ A real use of this is the addition of traces of water to a sample in CCl4 solution. Like this you can further confirm an alcohol, for example. $\endgroup$ – Alchimista Aug 9 '17 at 22:52