PART 15: ALIPHATIC AMINES (MASS SPECTRUM FRAGMENTATION PATTERN) FOR CSIR NET/GATE/M.Sc

In this, I have explained the interpretation of mass spectrum of aliphatic amines. Alpha cleavage is the main fragmentation pattern along with the 1,5 hydrogen shift. The presence of nitrogen in an amine can be detected by its odd molecular weight and the even fragments that it produces. Often times the presence of the molecular ion in longer straight chain amines is not detectable. Like alcohols, if the α carbon is bonded to a hydrogen atom, a [M – H] peak is usually visible. In primary amines with an unbranched α carbon, cleavage of the β bond produces a peak at m/z 30. This peak is not conclusive proof of a primary amine because secondary and tertiary amines undergo a rearrangement similar to that of alcohols. Amines also produce even fragments caused by the cleavage of C – C bonds farther away from the functional group. The fragment containing the nitrogen group usually retains the charge resulting peaks characterized by CnH2n+2N spaced at 14 units. There is also the less prevalent hydrocarbon pattern of CnH2n+1, CnH2n, and CnH2n-1. Cyclic amines produce a discernable molecular ion peak unless the α carbon is substituted. The loss of hydrogen from the α carbon is also a prominent peak. The ring is cleaved when the β bond is broken and subsequent alkene molecules fragment from the remaining ring structure. #MASSSPECTRUM #ALIPHATICAMINES #FRAGMENTATIONPATTERN