Question

Question: A common lab experiment is the dehydration of cyclopentanol tocyclopentene.

a. Explain how you could tell from the IR spectrum whether your product was pure cyclopentene, pure cyclopentanol or a mixture of cyclopentene and cyclopentanol. Give approximate frequencies for distinctive peaks.

b. Explain why mass spectrometry might not be a good way to distinguish cyclopentene from cyclopentanol.

Short answer

Answer

a) The compounds can be distinguished on the basis of IR peaks.

b) Mass spectrometry works of the process of fragmentation. Since the compounds are almost identical, mass spectrometry is not a better fit.

Step-by-step solution

IR Spectrum Peaks

a) IR spectrum can easily differentiate between cyclopentanol and cyclopentene.

Cyclopentanol contains alcohol as a functional group, whereas cyclypentene contains alkene as a functional group.

Pure cyclopentanol withbroad, sharp peat at 3200-3500cm^-1 and no stretch will be observed.

Pure cyclopentene will give stretch at 1620-1680cm^-1 and no broad stretch will be observed.

If it is a mixture of cyclopentanol and cyclopentene, then both broad stretch and stretch will be observed.

Mass Spectrometry

b) Mass spectrometry works on fragmentation of molecules. The structure of cyclopentanol and cyclopentene is almost similar. So, the fragmented molecules will be same and give almost similar peaks. Thus, mass spectrometry is not a good way to distinguish the two given compounds.

Conclusion

So the compounds, cyclopentanol and cyclopentene can be differentiated with IR but not with mass spectrometry.