Mass spectral fragmentation amines

An example of how information from fragmentation patterns can be used to solve structural problems is given in Worked Example 12.1. This example is a simple one, but the principles used are broadly applicable for organic structure determination by mass spectrometry. We ll see in the next section and in later chapters that specific functional groups, such as alcohols, ketones, aldehydes, and amines, show specific kinds of mass spectral fragmentations that can be interpreted to provide structural information. 

In several experimental papers dealing with the properties of 2-thiocytosine, usually the amine-thione form is assumed for the pyrimidine residue (e.g., ref. 80). Mass spectral fragmentation schemes of a number of s-triazines have been presented513 where 5-azathiocytosine has the amine-thione form. 

C. Mass and N.M.R. Spectra of Steroidal Amines.—A study has recently been made18 of the mass spectral fragmentation pattern of the dimer (28), obtained by reduction of the cyanamide of conanine with lithium aluminium hydride.19 As with certain benzylamines, a major fragment has been interpreted to arise from a heterolytic rupture of the C—N= bond. 

We ll see in the next section and in later chapters that specific fiinctional groups, such as alcohols, ketones, aldehydes, and amines, show specific kinds of mass spectral fragmentations that can be interpreted to provide structural information. 

The mass spectral fragmentation patterns of amines also aid in structural assignments. For example, the mass spectrum of V,V-diethylethanamine (triethylamine) shows the peak for the molecular ion at m/z = 101 (Figure 21-5). However, the more prominent base peak is at m/z = 86 and is caused by the loss of a methyl group by a-cleavage (Section 11-10). Such fragmentation is favored because it results in a resonance-stabilized iminium ion. 

Twelve volatile acyclic amines and amides (114-120,125-129) (Table VIII) from ponerine ants in the genus Mesoponera have been identified by gas chromatography-mass spectrometry and mass spectral comparison with authentic synthetic samples 41). The major aliphatic amine, A-isoamylnonylamine (114), shows a molecular ion at m/z 213, a-cleavage fragments at miz 156 (M — C4H9)... 

Derivatization of the reducing terminus, usually by reductive amination " (Figure 19.2), is necessary for detection of carbohydrates by optical methods and is frequently used for mass spectral analysis for purposes such as enhancement of signals or modification of fragmentation patterns. The reductive amination reaction with 2-aminopyridine (2-AP) can be reversed to recover the carbohydrate." Conversion to aminobenzoic acid alkyl esters increase hydrophobicity and can improve sensitivity, " " particularly for... 

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