Mass Spectra of Butyl Esters and N-Trifluoroacetyl Butyl Esters of Some Iminodicarboxylic Acids upon Electron Impact

Article abstract of DOI:10.1246/bcsj.57.1097

Mass spectra (electron impact at 20 eV) of butyl esters and N-trifluoroacetyl (TFA) butyl esters of some iminodicarboxylic acids (IDCAs) were determined by gas chromatography-mass spectrometry.The IDCAs included iminodiacetic acid (1), 2-(carboxymethylamino)propionic acid (2), 3-(carboxymethylamino)propionic acid (3), 2,2'-iminodipropionic acid (4), 2,3'-iminodipropionic acid (5), 3,3'-iminodipropionic acid (6), N-methylaminodiacetic acid (7), and nitrilotriacetic acid (8).The mass spectra of the butyl ester derivatives are simple, exhibiting the corresponding molecular (M⁺) ions with the exception of 5.The α,α'-IDCAs (1, 2, 4, 7, and 8) are characterized by M⁺, M -101 (COOC4H9) (base peak), and M - 157 (COOC4H9 + C4H8) ions.The β,β'-IDCA (6) is characterized by a more complex spectrum with M⁺, M - 73 (OC4H9), M - 115 (CH2COOC4H9) (base peak), M - 129 (OC4H9 + C4H9), and M - 171 (CH2COOC4H9 + C4H9) ions.The α,β'-IDCAs (3 and 5) in general show spectra in which both ions characteristic of α,α'- and β,β'-IDCAs are observed.The addition of TFA to the imino nitrogens of 1 - 6 increases complexity of the resulting spectra.In these instances, although M⁺ ions are usually present, neither M - 101 nor 115 ions are base peaks.The fragmentation pathways of these two volatile derivatives of the IDCAs upon electron impact are discussed.