Chapter 11 - Amines

Abstract

Amines are derivatives of ammonia, wherein one or more hydrogen atoms have been replaced by a substituent such as an alkyl or aryl group. Although capillary columns are generally preferred, there are many examples where separation is better by using packed columns, especially for low-boiling amines. This study concerns derivatization of amines and diamines and shows that MTBSTFA is the recommended reagent for silylation of the amine functionality because this reagent forms a more stable derivative than MSTFA, BSTFA, or BSA. The solvent used is important because amines can be difficult to silylate. A detailed description of mass spectral interpretation of amines is provided. Organic compounds with an odd number of nitrogen atoms will have an odd nominal mass; therefore, the M+• peak in the mass spectrum of compounds having an odd number of nitrogen atoms will be at an odd m/z value. Although EI mass spectrometry is considered to be the most reproducible of all the mass spectrometry techniques, this chapter presents an example, which is a good illustration of variabilities that can exist and have to be watched for in all GC/MS analyses. Underivatized aliphatic diamines are difficult to identify by their mass spectra alone because of the low abundance of the molecular ion.