Chemical ionization of amino acids. [H/sub 2/ chemical ionization mass spectra]

Journal Article · Wed Mar 17 00:00:00 EST 1976 · J. Am. Chem. Soc.; (United States)

DOI:https://doi.org/10.1021/ja00422a001· OSTI ID:7364382

Tsang, C W; Harrison, A G

The H/sub 2/ chemical ionization (CI) mass spectra of 14 ..cap alpha..-amino acids have been determined and compared with the CH/sub 4/CI mass spectra. The H/sub 2/ CI spectra show a much lower MH/sup +/ abundance and increased abundances of fragment ions formed by sequential fragmentation of MH/sup +/. The latter has potential advantages in determining the structure of R in RCH(NH/sub 2/)CO/sub 2/H. The CH/sub 4/ and H/sub 2/ CI mass spectra of ..beta..-alanine, 3-aminobutyric acid, 4-aminobutyric acid, and 6-amino-hexanoic acid also have been determined. For the ..beta..-amino acids, the dominant fragmentation of MH/sup +/ is sequential loss of H/sub 2/O and CH/sub 2/CO, while, for the terminal amino acids, MH/sup +/ fragments by loss of both NH/sub 3/ and H/sub 2/O. By using CD/sub 4/ as reagent gas it has been found that the peak previously attributed to loss of H/sub 2/O from MH/sup +/ in the CH/sub 4/ CI of ..cap alpha..-amino acids arises instead by C/sub 2/H/sub 5//sup +/ addition followed by the loss of the elements of formic acid. When R in RHC(NH/sub 2/)CO/sub 2/H contains a hydroxyl (including carboxyl) substituent loss of H/sub 2/O from MH/sup +/ is observed in addition to the ethyl ion addition reaction. Using both CD/sub 4/ and D/sub 2/ as reagent gases, it has been found that there is substantial deuterium retention in the ions originating from fragmentation of MD/sup +/. The results are not consistent with protonation at a specific site with the subsequent fragmentation being determined by the site of protonation, but rather indicate that there is extensive intramolecular proton transfer in MH/sup +/ prior to fragmentation. (auth)

• Research Organization: Univ. of Toronto
• OSTI ID: 7364382
• Journal Information: J. Am. Chem. Soc.; (United States), Vol. 98:6
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
ALANINES
IONIZATION
AMINO ACIDS
AMINOBUTYRIC ACID
ASPARTIC ACID
DEUTERIUM
ISOTOPE EFFECTS
GLYCINE
LEUCINE
METHIONINE
PHENYLALANINE
PROLINE
SERINE
THREONINE
TRYPTOPHAN
VALINE
FRAGMENTATION
HYDROGEN
MASS SPECTRA
METHANE
ALKANES
AMINES
AZOLES
CARBOXYLIC ACIDS
CRYOGENIC FLUIDS
ELEMENTS
FLUIDS
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
HYDROCARBONS
HYDROGEN ISOTOPES
HYDROXY ACIDS
INDOLES
ISOTOPES
LIGHT NUCLEI
LIPOTROPIC FACTORS
NONMETALS
NUCLEI
ODD-ODD NUCLEI
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANIC SULFUR COMPOUNDS
PYRROLES
PYRROLIDINES
SPECTRA
STABLE ISOTOPES
400302* - Organic Chemistry- Isotope Effects- (-1987)
400102 - Chemical & Spectral Procedures