| Abstract: | Various esters of choline and carnitine have been shown to undergo fragmentation dependent on both the structures of the molecules and the vapor and block temperatures when subjected to thermospray ionization mass spectrometry. The fragments observed vary with the structure of the ester portion and the backbone of the molecules, and are consistent with the compounds undergoing three types of reactions: (1) carbon—nitrogen bond cleavage to tertiary amines and alkyl compounds, (2) hydrolysis of the ester linkage, forming alcohols and organic acids, and (3) deacylation of the molecules to form acids and the corresponding quaternary alkene. The general applicability of the carbon—nitrogen bond cleavage mechanism was studied with other classes of quaternary compounds, but the sole products consistently detected for pyridinium, benzyldimethyldodecylammonium and tetraalkylammonium salts were amines. The fragments observed for the esters of choline and carnitine and also the anticholinergic 2,2-diphenyl-4-diisopropylaminobutyramide methiodide suggest that the mechanism of the thermospray fragmentation pathway is similar to that of the Hofmann elimination reaction. |
