Question

How can you distinguish isoborneol from camphor by mass spectrometry? They have very similar molecular weight.

Answer 1

High Resolution Mass Spectrometry (HRMS) can be used to determine molecular formula. Because HRMS can detect particle masses with an accuracy of 1/20,000 which is therefore, >0.0001 amu (atomic mass units). Thus this technique can be used to differentiate the compounds with similar rough mass but with a different molecular formula.

Camphor gets reduced to isoborneol through utilizing a reducing agent such as sodium borohydride. Isoborneol thus will have added hydrogens which could easily contribute to distinguish between it and the camphor via HRMS.

Thus different structures having same integer molecular weight but different chemical formulae can be distinguished using HRMS.¹H has 1.008 amu. HRMS can distinguish till 0.01 amu. So it is obvious that isoborneol and camphor could be easily distinguished by HRMS.