Functional groups identification with fragmentations

Until the second half of the twentieth century, the structure of a substance—a newly discovered natural product, for example—was determined using information obtained from chemical reactions. This information included the identification of functional groups by chemical tests, along with the results of experiments in which the substance was broken down into smaller, more readily identifiable fragments. Typical of this approach is the demonstration of the presence of a double bond in an alkene by catalytic hydrogenation and subsequent determination of its location by ozonolysis. After-considering all the available chemical evidence, the chemist proposed a candidate structure (or structures) consistent with the observations. Proof of structure was provided either by converting the substance to some already known compound or by an independent synthesis. 

If preliminary results indicate the presence of a Scheduled chemical, which is not in the spectral libraries, its structure elucidation is carried out. The GC/EI/MS, GC/CI/MS, and LC/MS spectra are interpreted. Molecular weight and presence of heteroatoms like sulfur, chlorine, and phosphorus is determined. GC/HRMS and LC/MS/MS assist in interpretation of the fragmentation of ions of interest. Elemental composition of the molecular and fragment ions can be determined with GC/HRMS. Interpretation of GC/FTIR spectrum provides information on functional groups (when reporting in a PT, note that IR spectrum interpretation is not considered sufficient for identification), and the different... 

---